220–325GHz All-Photopolymer Bragg Horn Antennas Towards Eco-Friendly Terahertz Applications

220–325GHz All-Photopolymer Bragg Horn Antennas Towards Eco-Friendly Terahertz Applications | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article 220–325GHz All-Photopolymer Bragg Horn Antennas Towards Eco-Friendly Terahertz Applications Nonchanutt Chudpooti, Binbin Hong, Rungrat Viratikul, Feaveya Kheawprae, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6221054/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 30 Jul, 2025 Read the published version in Scientific Reports → Version 1 posted 14 You are reading this latest preprint version Abstract This paper presents the development of the world’s first high-gain, all-photopolymer Bragg horn antennas explicitly designed for the WR-3.4 band (220–325GHz), marking a groundbreaking advancement in terahertz (THz) antenna technology. Unlike conventional metallic horn antennas, which suffer from conductor losses and manufacturing complexity, this innovative design utilizes eco-friendly photopolymer materials and additive manufacturing, achieving a fractional bandwidth of 38.5% that fully covers the WR-3.4 band. The proposed antenna achieves a measured peak gain of 28.98 dBi at 300GHz, with a return loss better than − 20dB across the band and a consistent half-power beamwidth (HPBW) of ~ 5°, ensuring precise directivity and minimal sidelobe interference. By employing a novel horn-type adapter for seamless mode conversion from TE 10 to the fundamental HE 11 mode, the design significantly enhances coupling efficiency and reduces signal loss. Additionally, fabrication costs can be reduced by over 50% compared to traditional metallic designs, while maintaining repeatability and enabling rapid prototyping. As the first demonstration of photopolymer-based antennas achieving such high gains in the 220-325GHz THz spectrum, this work establishes a new benchmark in THz antenna technology, providing an eco-friendly, cost-effective, and high-performance solution for high-speed communication, medical diagnostics, security imaging, and spectroscopy applications. Physical sciences/Engineering Physical sciences/Engineering/Electrical and electronic engineering All-photopolymer horn antenna Bragg structure THz antennas Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction Recently, terahertz (THz) technology has attracted significant attention from researchers and engineers worldwide due to its vast potential across various applications, including high-resolution radar systems, imaging, sensing, security scanning, and high-speed communication networks [1]–[10]. Antennas play a critical role in realizing these applications. Over the years, numerous THz antenna designs have been proposed, such as horn antennas, slotted waveguide antennas, reflector antennas, and dielectric lens antennas [11]–[18]. Among these, dielectric lens antennas stand out for THz applications owing to their straightforward design, high gain, broad bandwidth, immunity to conductor losses, and ability to support circular polarization [19]–[28]. However, achieving efficient operation in the 220–325 GHz frequency range remains challenging. Traditional metallic horn antennas, optimized for lower frequencies, struggle to effectively handle THz radiation due to wavelength disparities. This impedance mismatch results in suboptimal signal transmission and reception, ultimately constraining the performance of THz technology. In comparison to conventional metallic horn antennas, all-photopolymer Bragg Horn Antennas offer numerous advantages within the THz spectrum. These antennas demonstrate exceptional efficiency in signal transmission and reception, significantly enhancing the performance of THz technology. Their intrinsic miniaturization capability facilitates seamless integration into compact THz devices and systems, aligning with the growing demand for smaller and more efficient components in THz technology. Furthermore, these antennas provide precise control over radiation patterns, making them highly adaptable for diverse THz applications, including high-speed wireless communication, advanced THz imaging for medical diagnostics and security scanning, and precise spectroscopy for chemical analysis. Notably, their material properties are meticulously optimized to ensure superior performance across the THz frequency range. All-photopolymer Bragg horn antennas offer several noteworthy advantages. They excel in repeatability and accuracy, ensuring consistent and precise results in terahertz measurements. Additionally, their user-friendly design simplifies setup and operation, reducing the complexity of measurement procedures and making them accessible to researchers and technicians. These antennas are also cost-effective, providing an economical solution for THz measurements compared to many conventional techniques. Their inherent miniaturization capabilities enable seamless integration into compact THz devices and systems, aligning with the ongoing trend toward miniaturization in THz technology and fostering the development of portable and efficient THz solutions. Notably, their ability to provide precise control over radiation patterns enhances their versatility, making them suitable for a wide range of THz applications. In [11], an all-dielectric terahertz horn antenna based on a hollow-core electromagnetic crystal structure (EMXT) was presented. The antenna operates in the frequency range of 100–190 GHz, with a reflection coefficient (S 11 ) lower than -30 dB. To optimize the horn antenna, key parameters such as the flare length and flare angle were investigated through parameter sweeps, allowing performance comparisons. This design employed a time-domain spectroscopy (TDS) transmitter as the feeding network. However, using a TDS transmitter presents practical challenges, as it requires experienced personnel for precise setup and calibration, which may be difficult for beginners. Furthermore, the high-precision alignment necessary for this antenna demands specialized scales and precision tools, potentially increasing setup complexity and cost. This paper provides a comprehensive exploration of the 220–325 GHz all-photopolymer Bragg horn antennas, presenting a novel approach to advancing THz antenna technology. It examines the underlying principles, design considerations, and advantages of this innovative technology. By integrating theoretical analysis, numerical simulations, and experimental validation, the study demonstrates the ability of these antennas to deliver high-performance radiation characteristics within the challenging THz frequency range. The proposed design holds significant promise for a wide range of applications, including high-speed wireless communication, advanced THz imaging for medical diagnostics and security scanning, precise spectroscopy for chemical analysis, and improved quality control processes across various industrial sectors. The distinctiveness of this research lies in its dedicated focus on the 220–325 GHz frequency range within the THz spectrum, a band that remains underrepresented in existing technologies. By leveraging all-photopolymer materials instead of traditional metallic horn antennas, this work introduces groundbreaking innovations. These advancements result in improved efficiency, enhanced miniaturization capabilities, precise radiation control, and optimized material properties tailored specifically for the challenging demands of the THz spectrum. This targeted and innovative approach paves the way for exploring new applications in high-speed communication, advanced THz imaging, precise chemical analysis, and improved quality control across diverse industries. In addition to their numerous advantages, these antennas exhibit material properties specifically optimized for operation within the THz frequency range. These optimizations include favorable permittivity and permeability characteristics, which significantly enhance antenna performance and establish a clear advantage over traditional metallic horn antennas. However, it is important to note that while all-photopolymer Bragg horn antennas deliver exceptional performance in the millimeter-wave (mmWave) and THz frequency ranges, their applicability at lower frequencies is inherently limited. This limitation arises from their precisely engineered design, which is tailored to the shorter wavelengths characteristic of the THz spectrum. 2. Design and Fabrication of All-Photopolymer Bragg Horn Antennas 2.1 Design of All-Photopolymer Bragg Horn Antennas All-photopolymer Bragg horn antennas, fabricated from Accura ClearVue [29], are specialized devices designed for operation in the terahertz (THz) frequency range, specifically between 220 GHz and 325 GHz. These antennas stand out due to their non-metallic construction, which makes them highly suitable for THz applications. Their unique horn-shaped design plays a critical role in precisely controlling signal emission, facilitating their use in various advanced fields. Figure 1(a) illustrates the perspective geometry of the Bragg fiber horn antenna integrated with the horn-type adapter [29]. Within the Bragg fiber structure, the outermost layer—measuring 4.6 mm in thickness with a support bridge width of 0.64 mm—serves as a robust protective polymer layer. This layer enhances mechanical stability, provides resistance to environmental conditions, absorbs residual electromagnetic waves, and effectively shields the fiber from external interference [29]. The horn-type adapter serves as a critical component, connecting a standard WR-3.4 waveguide to a Bragg fiber through its input aperture. It facilitates the conversion of the TE 10 mode from the rectangular waveguide into the fundamental HE 11 mode within the Bragg fiber, which is characterized by linear polarization [29]. Unlike the input mode described in [30], which corresponds to a free-space Gaussian beam, the mode in this work is a circular waveguide mode at the output aperture of the horn-type adapter. This hybrid mode consists of multiple competing components, with the fundamental TE 11 mode of the hollow metallic circular waveguide (HMCW) being the primary mode. Achieving proper phase matching is essential for minimizing signal loss and reflection, thereby ensuring efficient electromagnetic energy transfer between the waveguides. Effective phase matching allows seamless energy propagation from the horn-type adapter to the THz Bragg fiber, significantly enhancing measurement accuracy and reliability. Figure 1(b) provides a cross-sectional view of the all-photopolymer Bragg horn antenna, with the key parameters of both the Bragg fiber horn and the horn-type adapter summarized in Table I. The design of the Bragg horn antenna centers on three critical parameters: the flare angle (θ), the aperture length ( A L ), and the flare horn length ( F L ). However, due to the interdependence between the flare angle and the aperture length, this study focuses on varying the flare angle (θ) to assess the antenna's performance. The evaluation considers the reflection coefficient (S 11 ), radiation pattern, and realized gain of the antenna at 0°. In this study, the CST Studio Suite [31] was utilized to optimize the design parameters of the all-photopolymer Bragg horn antenna. The horn extension length was fixed at 100 mm to facilitate the transition of the electromagnetic field into the fundamental HE 11 mode within the Bragg fiber [30]. Additionally, the flare horn length (FL) was set at 50 mm to minimize insertion loss in the hollow Bragg fiber. As a result, the flare angle (θ) was identified as the primary variable for optimizing the gain performance of the Bragg fiber antenna. Figure 2 illustrates the simulated results for varying the flare angle from 5° to 30°. As shown in Figure 2(a), the reflection coefficient (S 11 ) across the full operating band of 220–325 GHz is slightly higher for a flare angle of 30° compared to 5° and 15°. Despite this, the antenna exhibits favorable performance, maintaining S 11 values below -20 dB across the entire band. Figure 2(b) presents the simulated realized gain of the Bragg fiber horn antenna at 0° for the three flare angles: 5°, 15°, and 30°. The results reveal that all configurations achieve a realized gain exceeding 20 dBi across the band, with the 5° flare angle delivering the highest performance. For the 5° configuration, the realized gain surpasses 25.3 dBi throughout the band, peaking at 29.48 dBi at 300 GHz. Figure 3 depicts the radiation patterns at three sampling frequencies—220 GHz, 270 GHz, and 320 GHz—representing the lower, middle, and upper frequencies of the WR-3.4 band, respectively. At 220 GHz, the maximum gains achieved for the three flare angles (5°, 15°, and 30°) are 25.3 dBi, 22.0 dBi, and 20.2 dBi, with corresponding half-power beamwidths (HPBWs) of 6.7°, 10.9°, and 15.4°. At the center frequency of 270 GHz, the maximum gains for the same flare angles are 26.0 dBi, 25.2 dBi, and 22.0 dBi, with HPBWs of 5.6°, 6.3°, and 11.1°, respectively. At 320 GHz, representing the upper end of the operating band, the maximum gains for the three configurations are 29.0 dBi, 28.6 dBi, and 25.2 dBi, with corresponding HPBWs of 4.3°, 4.5°, and 5.2°. The simulation results for the three evaluated parameters—reflection coefficient (S 11 ), realized gain at 0°, and radiation patterns across flare angles of 5°, 15°, and 30°—indicate that the Bragg fiber horn antenna with a 5° flare angle delivers the best overall performance under all conditions. This configuration consistently outperforms the other flare angles in terms of gain, efficiency, and beamwidth, making it the optimal choice for the studied frequency range. 2.2 Fabrication of All-Photopolymer Bragg Horn Antennas The fabrication process of the Bragg fiber horn antenna began with its design, which was meticulously developed using CST simulation software to optimize performance parameters. The finalized design was then implemented using a 3D Systems PolyJet 7000 HD 3D printer, leveraging the stereolithography technique to achieve high precision in manufacturing the all-photopolymer structure. Following this, the horn-type adapter was fabricated using CNC milling to ensure dimensional accuracy and surface quality. A copper connector was specifically flared to match the diameter of the Bragg fiber, ensuring proper alignment and minimal signal loss. The CNC milling process provided the precision necessary to meet the design specifications and facilitated seamless integration of the adapter with the Bragg fiber horn antenna. The final assembly, depicted in Figure 4, features an all-photopolymer Bragg horn antenna optimized for the 220–325 GHz frequency range. The design includes a flare angle of 5°, which was selected for its superior performance in simulations, and integrates efficiently with the horn-type adapter to enhance overall functionality. 3. Measurement Results To evaluate the performance of the all-photopolymer Bragg horn antenna, measurements were conducted using a Keysight Technologies PNA-X N5242 Vector Network Analyzer (VNA), equipped with two OML WR-3.4 frequency extender heads. These measurements included the reflection coefficient (S 11 ) and radiation pattern over the 220–325 GHz frequency range. The Line-Reflect-Line (LRL) calibration technique was employed to ensure accurate and reliable data across the operating band. A laser alignment system, commonly utilized in terahertz (THz) measurements, was implemented to achieve precise alignment and controlled rotation of the antenna during testing, minimizing alignment errors and enhancing measurement accuracy. The measurement setup, illustrated in Figure 5, consists of a standard conical horn antenna connected to a WR-3.4 frequency extender acting as the transmitter (Tx) and the all-photopolymer Bragg horn antenna, integrated with a horn-type adapter and WR-3.4 frequency extender, serving as the receiver (Rx) and antenna under test (AUT). This configuration ensured a controlled and repeatable environment for assessing the antenna's performance metrics. Figure 6 compares the measured and simulated results for the reflection coefficient (S 11 ) across the full WR-3.4 frequency band (220–325 GHz). The data confirm that the antenna design achieves excellent performance, maintaining an S 11 value consistently below -20 dB across the entire band. This indicates minimal signal reflection and efficient energy transfer. The results also highlight a fractional bandwidth of approximately 38.5%, underscoring the antenna's capability to operate effectively over a broad frequency range while meeting the stringent requirements of THz applications. The broadband gain of the proposed all-photopolymer Bragg horn antenna was determined by recording the transmission coefficients (S 21 ) and using them to calculate the realized gain in units of dBi. Figure 7 illustrates the comparison between the simulated and measured realized gain of the antenna across the 220–320 GHz frequency range, with data collected at 10 GHz intervals. Table II provides the detailed results, including the calculated percentage differences between the simulated and measured values. The findings indicate that the maximum error between the simulated and measured gain is within 4.28%, demonstrating the high accuracy and reliability of the measurement system employed in this study. These results validate the robustness of the design and the effectiveness of the testing methodology. For radiation pattern measurements, a WR-3.4 horn antenna with a nominal gain of 26 dBi and a half-power beamwidth (HPBW) of 10° was utilized as the standard reference antenna. The radiation characteristics of the all-photopolymer Bragg horn antenna were measured using a Keysight VNA equipped with frequency extender heads. Precise antenna positioning and rotation during the measurements were ensured using a laser alignment system, which minimized alignment errors and enhanced measurement accuracy. The test setup maintained a 50 mm separation between the antenna under test (AUT) and the reference antenna, a distance exceeding the simulated far-field requirement for the upper frequency of 320 GHz. The AUT was manually rotated and adjusted across a range of angles from −45° to +45°. Within the central range of −10° to +10°, 1° increments were used, while 5° increments were applied for the wider range of ±10° to ±45°. This controlled rotation ensured comprehensive angular coverage for the evaluation. The radiation pattern of the Bragg fiber horn antenna was measured at three representative frequencies—220 GHz, 270 GHz, and 320 GHz—corresponding to the lower, middle, and upper ranges of the WR-3.4 band (220–325 GHz). Figure 8 (a)–(c) illustrates the normalized comparison between the measured and simulated radiation patterns of the antenna at these frequencies, highlighting the performance and agreement between the two datasets. The results indicate that the radiation pattern shows a strong correlation between the simulated and measured data within the angular range of −30° to +30°. This agreement highlights the accuracy of the antenna design and measurement setup in capturing the intended performance characteristics. However, beyond ±30°, a noticeable mismatch is observed between the simulated and measured results. This discrepancy is attributed to significant free-space path loss, which reduces the dynamic range of the VNA and impacts the accuracy of measurements in these angular regions. The antenna design presented in this work strikes an effective balance between achieving high gain and maintaining a compact form factor, while carefully accounting for the material loss characteristics of the chosen photopolymer. Although higher realized gains could potentially be obtained using lower-loss materials such as high-resistivity silicon or GaAs, these alternatives come with significantly higher costs and require complex manufacturing processes, such as those involving advanced cleanroom facilities. In contrast, the additive manufacturing approach employed in this study, particularly the 3D-printing technique, offers a simpler, more accessible fabrication method that is well-suited for rapid prototyping and mass production at substantially reduced costs. This approach not only simplifies the production process but also aligns with the growing demand for eco-friendly and cost-effective solutions in terahertz (THz) technology. Table III provides a detailed comparison of eight key performance parameters—including structure, coupling efficiency, repeatability, user expertise requirements, fabrication and material costs, and environmental impact—between the THz antenna proposed in this work and other state-of-the-art designs reported in the literature [32]–[40]. 4. Conclusion This study introduces the all-photopolymer Bragg horn antenna, specifically designed to operate within the WR-3.4 band, covering the 220–325 GHz frequency range. To evaluate its performance, three flare horn angles—5°, 15°, and 30°—were analyzed and compared based on key parameters, including the reflection coefficient (S 11 ), realized gain, and half-power beamwidth (HPBW). To address coupling challenges resulting from the mismatch between the WR-3.4 aperture and the Bragg fiber aperture, a horn-type adapter was employed. This adapter facilitates the transition by connecting the standard WR-3.4 waveguide to the Bragg fiber input aperture, converting the TE 10 mode from the rectangular waveguide into the fundamental HE 11 mode within the Bragg fiber. Experimental results demonstrate that the all-photopolymer Bragg horn antenna achieves a fractional bandwidth of 38.5%, effectively covering the entire WR-3.4 band. The antenna exhibits a measured peak gain of approximately 28.98 dBi at 0°, a return loss better than −20 dB across the operating band, and a consistent HPBW of approximately 5° throughout the WR-3.4 frequency range. Declarations CRediT authorship contribution statement Nonchanutt Chudpooti: Writing – review & editing, Writing – original draft, Validation, Resources, Investigation, Formal analysis, Data curation. Rungrat Viratikul: Writing – original draft. Binbin Hong: Conceptualization, Project administration. Feaveya Kheawprae: Methodology. Akkarat Boonpoonga: Supervision. Panuwat Janpugdee: Supervision, Funding acquisition. Weijia Zhan: Supervision. Prayoot Akkaraekthalin: Supervision, Funding acquisition. Joachim Oberhammer: Supervision. Nutapong Somjiti: Writing – review & editing, Conceptualization, Funding acquisition. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper Acknowledgements This research was supported in part by the National Natural Science Foundation of China under Grant 62105213; in part by Guangdong Basic and Applied Basic Research Fund under Grant 2020A1515111037; in part by the National Science, Research and Innovation Fund (NSRF), and King Mongkut’s University of Technology North Bangkok, under Contract KMUTNB-FF-67-A-02; in part by the Ph.D. Matching Fund granted by the Electrical Engineering Department, Chulalongkorn University; in part by the Engineering and Physical Science Research Council under Grant EP/S016813/1; and in part by the Swedish Research Council (VR) under Grant 2021-05842_VR. Data availability Data will be made available on request. References Cooper, K. B. et al. A high-resolution imaging radar at 580 GHz. 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Tables Table 1: The Key Parameters of the All-Photopolymer Bragg Horn Antennas and Horn-Type Adapter Parameter Description Value A L Aperture length 55.60, 73.65, 104.58 mm F L Flare horn length 50 mm H L Horn extension length 100 mm θ Flare angle 5, 15, 30 degrees W L WR-3.4 aperture length 3 mm T L Tapered length 45.3 mm L 1 Horn-type adapter length 53 mm W 1 Horn-type adapter width 50 mm H 1 Horn-type adapter height 50 mm Table 2: The Calculated Comparison Results of Simulated and Measured Realized Gain at 0 degree Frequency (GHz) Simulated realized gain (dBi) Measured realized gain (dBi) Error (%) 220 25.31 24.61 2.77 230 25.72 25.19 2.06 240 25.85 25.53 1.24 250 26.10 25.74 1.38 260 26.31 25.83 1.82 270 26.67 25.91 2.85 280 28.14 27.72 1.49 290 29.07 28.67 1.38 300 29.48 28.98 1.70 310 29.39 28.92 1.60 320 28.98 27.74 4.28 Table 3: Comparisons of Key Properties between Different THz Antennas Ref. No. Antenna Structure Operating Band (THz) Coupling efficiency Measurement repeatability Operator experience requirement Fabrication cost Material Cost Eco-Friendly Material [32] Multi-angle Horn 1.7-2.1 Medium Repeatable High High High Non-biodegradable [33] Corrugated conical horn 0.211-0.275 High Repeatable High High High Non-biodegradable [34] 3D-printed back-to-back horn 0.22-0.325 Medium Repeatable High High High Non-biodegradable [35] Hemispherical lens antennas 0.22-0.32 Medium Repeatable High Low Low Non-biodegradable [36] Integrated an E -plane flare and dual H -plane reflectors 0.325-0.5 Medium Repeatable High Low High Non-biodegradable [37] Step-profiled corrugated horn antennas integrated in LTCC 0.242-0.33 Medium Repeatable High High Low Non-biodegradable [38] Pyramidal horn antenna 0.191 Medium Repeatable High High High Non-biodegradable [39] Circularly polarized antennas 0.22-0.32 Medium Repeatable High High High Non-biodegradable [40] Metallic lens antenna 0.37-0.46 Medium Repeatable High Low High Non-biodegradable This work All-photopolymer Bragg Horn Antenna 0.22-0.325 High Highly Repeatable Low Low Low Biodegradable Additional Declarations No competing interests reported. Supplementary Files DataFigure7.xlsx DataFigure2b.xlsx DataFigure3.xlsx DataFigure8.xlsx DataFigure6.xlsx DataFigure2a.xlsx Cite Share Download PDF Status: Published Journal Publication published 30 Jul, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 05 May, 2025 Reviews received at journal 23 Apr, 2025 Reviews received at journal 19 Apr, 2025 Reviews received at journal 09 Apr, 2025 Reviewers agreed at journal 04 Apr, 2025 Reviewers agreed at journal 04 Apr, 2025 Reviewers agreed at journal 03 Apr, 2025 Reviewers agreed at journal 31 Mar, 2025 Reviewers agreed at journal 30 Mar, 2025 Reviewers invited by journal 30 Mar, 2025 Editor assigned by journal 26 Mar, 2025 Editor invited by journal 26 Mar, 2025 Submission checks completed at journal 26 Mar, 2025 First submitted to journal 26 Mar, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6221054","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":440673387,"identity":"a85b54fa-b7ab-4979-9838-aa9366ebeafd","order_by":0,"name":"Nonchanutt Chudpooti","email":"","orcid":"","institution":"King Mongkut’s University of Technology North Bangkok","correspondingAuthor":false,"prefix":"","firstName":"Nonchanutt","middleName":"","lastName":"Chudpooti","suffix":""},{"id":440673388,"identity":"2d36ede9-e2f1-460c-8a88-47fd57ebc115","order_by":1,"name":"Binbin Hong","email":"","orcid":"","institution":"Beijing Normal University","correspondingAuthor":false,"prefix":"","firstName":"Binbin","middleName":"","lastName":"Hong","suffix":""},{"id":440673389,"identity":"2251c4d0-683a-43b8-93e8-809174882a35","order_by":2,"name":"Rungrat Viratikul","email":"","orcid":"","institution":"Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Rungrat","middleName":"","lastName":"Viratikul","suffix":""},{"id":440673390,"identity":"41b5cf75-af3f-4a4a-952d-e08c0f0bbd5d","order_by":3,"name":"Feaveya Kheawprae","email":"","orcid":"","institution":"King Mongkut’s University of Technology North Bangkok (Rayong Campus)","correspondingAuthor":false,"prefix":"","firstName":"Feaveya","middleName":"","lastName":"Kheawprae","suffix":""},{"id":440673391,"identity":"c06b4606-1fab-40ab-9a8b-ffa101dab3a1","order_by":4,"name":"Akkarat Boonpoonga","email":"","orcid":"","institution":"King Mongkut’s University of Technology North Bangkok","correspondingAuthor":false,"prefix":"","firstName":"Akkarat","middleName":"","lastName":"Boonpoonga","suffix":""},{"id":440673392,"identity":"cbe11157-b20e-4747-9a31-a8676a065147","order_by":5,"name":"Panuwat Janpugdee","email":"","orcid":"","institution":"Chulalongkorn University","correspondingAuthor":false,"prefix":"","firstName":"Panuwat","middleName":"","lastName":"Janpugdee","suffix":""},{"id":440673393,"identity":"71181768-a7c2-4f99-94f1-2cd900eb98bd","order_by":6,"name":"Weijia Zhang","email":"","orcid":"","institution":"Shaoxing University","correspondingAuthor":false,"prefix":"","firstName":"Weijia","middleName":"","lastName":"Zhang","suffix":""},{"id":440673394,"identity":"d26616b9-0f55-4a8c-9157-d36493f7843f","order_by":7,"name":"Prayoot Akkaraekthalin","email":"","orcid":"","institution":"King Mongkut’s University of Technology North Bangkok","correspondingAuthor":false,"prefix":"","firstName":"Prayoot","middleName":"","lastName":"Akkaraekthalin","suffix":""},{"id":440673395,"identity":"e473f78f-bc44-415d-92c2-925460c3f17c","order_by":8,"name":"Joachim Oberhammer","email":"","orcid":"","institution":"KTH Royal Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Joachim","middleName":"","lastName":"Oberhammer","suffix":""},{"id":440673396,"identity":"82e5f659-dabb-4b34-8731-edece02efe8e","order_by":9,"name":"Nutapong Somjit","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA00lEQVRIiWNgGAWjYNACHgkGfnYQDeEyE6VFQrKZNC0MDBIGh4nVYs7A/vDRDRmLOuPDzAcfvPnDIM/fwGNsgE+LJVCBcQ7QYWaH2ZIN57YxGM44wGOcgE+LwQEeNmmIFh4zad4GBsYNDDzGB/BrYX8G1mLczP/9N88fBnsitDCYgbUYMPOwARFDIkgLfocdhvhFcsZhNmPJuW0SyUBGMV7vGxxvf/g4t6eOn7+9+eGHN39sbPvbmzdL4NMCjgPGHjhXgtiI/EGUqlEwCkbBKBipAAAAfzlVNo2x4gAAAABJRU5ErkJggg==","orcid":"","institution":"University of Leeds","correspondingAuthor":true,"prefix":"","firstName":"Nutapong","middleName":"","lastName":"Somjit","suffix":""}],"badges":[],"createdAt":"2025-03-13 14:38:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6221054/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6221054/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-025-11978-9","type":"published","date":"2025-07-30T16:20:59+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":81022775,"identity":"20db7660-be6a-4610-a8c2-035091fe9712","added_by":"auto","created_at":"2025-04-21 10:05:13","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":842557,"visible":true,"origin":"","legend":"\u003cp\u003eThe geometry of the 220–325 GHz all-photopolymer Bragg horn antenna, consisting of two components: the horn-type adapter and the all-photopolymer Bragg horn antenna (a) perspective view and (b) The cross-sectional view in \u003cem\u003eYZ\u003c/em\u003e-plane.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/28b9b84d45fa6c07f66d26d8.jpeg"},{"id":81024255,"identity":"d203a541-86b3-48f9-b8a9-fd5d8b228042","added_by":"auto","created_at":"2025-04-21 10:13:13","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":670768,"visible":true,"origin":"","legend":"\u003cp\u003eSimulated parametric study of the flare angle, \u003cem\u003eθ\u003c/em\u003e, for (a) reflection coefficient, \u003cem\u003eS\u003c/em\u003e\u003csub\u003e11\u003c/sub\u003e, and (b) realized gain of antenna at 0 degree.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/b2272a048d85477a4394683a.jpeg"},{"id":81024254,"identity":"26d489e3-70c6-4e00-bfb4-a5324ca5a7e8","added_by":"auto","created_at":"2025-04-21 10:13:13","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":153968,"visible":true,"origin":"","legend":"\u003cp\u003eThe simulated radiation patterns for three flare angle (𝜃) configurations of 5 degrees, 15 degrees, and 30 degrees at (a) 220 GHz, (b) 270 GHz, and (c) 320 GHz.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/40588edc476a995c2d1e4619.jpg"},{"id":81025107,"identity":"e545dbcd-4cc6-436c-8b6c-c85ccdd641b4","added_by":"auto","created_at":"2025-04-21 10:29:13","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1133049,"visible":true,"origin":"","legend":"\u003cp\u003eThe fabricated 220–325 GHz all-photopolymer Bragg horn antenna with a flare angle of 5 degrees, integrated with the horn-type adapter.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/0c7f8bac79c10e054c590ede.jpg"},{"id":81022785,"identity":"b12262ea-04af-42d2-9fb7-06e568f3ea82","added_by":"auto","created_at":"2025-04-21 10:05:13","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":143258,"visible":true,"origin":"","legend":"\u003cp\u003eMeasurement setup used in this study, comprising a standard conical horn antenna in the transmitter section (T\u003csub\u003ex\u003c/sub\u003e) and the all-photopolymer Bragg horn antenna in the receiver section (R\u003csub\u003ex\u003c/sub\u003e), serving as the antenna under test (AUT).\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/43e8d313fc924bffc3312834.jpg"},{"id":81022788,"identity":"f14ce446-6e55-4707-a25a-e15c9cd8d228","added_by":"auto","created_at":"2025-04-21 10:05:13","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":580828,"visible":true,"origin":"","legend":"\u003cp\u003eThe comparison results of simulated and measured reflection coefficient, S\u003csub\u003e11\u003c/sub\u003e for the whole WR-3.4 band (220 – 325 GHz).\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/c274182cdc8254cef34b7684.jpg"},{"id":81022782,"identity":"e3b39a1a-c8d2-419c-8f34-da3248059791","added_by":"auto","created_at":"2025-04-21 10:05:13","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":21335,"visible":true,"origin":"","legend":"\u003cp\u003eThe comparison results of simulated and measured realized gain at 0 degree for the whole WR-3.4 band (220 – 325 GHz).\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/8c72ccac4ea01e84fda36b2c.jpg"},{"id":81024261,"identity":"04ce98b9-1d42-4a6e-835a-49de21aee7cb","added_by":"auto","created_at":"2025-04-21 10:13:13","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":121659,"visible":true,"origin":"","legend":"\u003cp\u003eThe simulated and measured radiation patterns for flare angle (𝜃) configurations of 5 degrees at (a) 220 GHz, (b) 270 GHz, and (c) 320 GHz.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/1a586794df352d14f0a9dfcd.jpg"},{"id":88268197,"identity":"bf6ca3cb-faa5-449d-9a14-f9bc6d5946c1","added_by":"auto","created_at":"2025-08-04 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10:21:13","extension":"xlsx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":33520,"visible":true,"origin":"","legend":"","description":"","filename":"DataFigure8.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/8ffb463261984c58021c4a78.xlsx"},{"id":81024509,"identity":"30fd6dcc-4325-407e-a430-911471c219c6","added_by":"auto","created_at":"2025-04-21 10:21:13","extension":"xlsx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":46033,"visible":true,"origin":"","legend":"","description":"","filename":"DataFigure6.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/3553e48a6d0afe565c1d9df2.xlsx"},{"id":81022786,"identity":"89668ec2-9fd9-49c0-958a-2114e959f774","added_by":"auto","created_at":"2025-04-21 10:05:13","extension":"xlsx","order_by":5,"title":"","display":"","copyAsset":false,"role":"supplement","size":49799,"visible":true,"origin":"","legend":"","description":"","filename":"DataFigure2a.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6221054/v1/b7f6c889bdaa5030282f8bb3.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"220–325GHz All-Photopolymer Bragg Horn Antennas Towards Eco-Friendly Terahertz Applications","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eRecently,\u0026nbsp;terahertz (THz) technology has attracted significant attention from researchers and engineers worldwide due to its vast potential across various applications, including high-resolution radar systems, imaging, sensing, security scanning, and high-speed communication networks [1]–[10]. Antennas play a critical role in realizing these applications. Over the years, numerous THz antenna designs have been proposed, such as horn antennas, slotted waveguide antennas, reflector antennas, and dielectric lens antennas [11]–[18]. Among these, dielectric lens antennas stand out for THz applications owing to their straightforward design, high gain, broad bandwidth, immunity to conductor losses, and ability to support circular polarization [19]–[28]. However, achieving efficient operation in the 220–325 GHz frequency range remains challenging. Traditional metallic horn antennas, optimized for lower frequencies, struggle to effectively handle THz radiation due to wavelength disparities. This impedance mismatch results in suboptimal signal transmission and reception, ultimately constraining the performance of THz technology.\u003c/p\u003e\n\u003cp\u003eIn comparison to conventional metallic horn antennas, all-photopolymer Bragg Horn Antennas offer numerous advantages within the THz spectrum. These antennas demonstrate exceptional efficiency in signal transmission and reception, significantly enhancing the performance of THz technology. Their intrinsic miniaturization capability facilitates seamless integration into compact THz devices and systems, aligning with the growing demand for smaller and more efficient components in THz technology. Furthermore, these antennas provide precise control over radiation patterns, making them highly adaptable for diverse THz applications, including high-speed wireless communication, advanced THz imaging for medical diagnostics and security scanning, and precise spectroscopy for chemical analysis. Notably, their material properties are meticulously optimized to ensure superior performance across the THz frequency range.\u003c/p\u003e\n\u003cp\u003eAll-photopolymer Bragg horn antennas offer several noteworthy advantages. They excel in repeatability and accuracy, ensuring consistent and precise results in terahertz measurements. Additionally, their user-friendly design simplifies setup and operation, reducing the complexity of measurement procedures and making them accessible to researchers and technicians. These antennas are also cost-effective, providing an economical solution for THz measurements compared to many conventional techniques. Their inherent miniaturization capabilities enable seamless integration into compact THz devices and systems, aligning with the ongoing trend toward miniaturization in THz technology and fostering the development of portable and efficient THz solutions. Notably, their ability to provide precise control over radiation patterns enhances their versatility, making them suitable for a wide range of THz applications.\u003c/p\u003e\n\u003cp\u003eIn [11], an all-dielectric terahertz horn antenna based on a hollow-core electromagnetic crystal structure (EMXT) was presented. The antenna operates in the frequency range of 100–190 GHz, with a reflection coefficient (S\u003csub\u003e11\u003c/sub\u003e) lower than -30 dB. To optimize the horn antenna, key parameters such as the flare length and flare angle were investigated through parameter sweeps, allowing performance comparisons. This design employed a time-domain spectroscopy (TDS) transmitter as the feeding network. However, using a TDS transmitter presents practical challenges, as it requires experienced personnel for precise setup and calibration, which may be difficult for beginners. Furthermore, the high-precision alignment necessary for this antenna demands specialized scales and precision tools, potentially increasing setup complexity and cost.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis paper provides a comprehensive exploration of the 220–325 GHz all-photopolymer Bragg horn antennas, presenting a novel approach to advancing THz antenna technology. It examines the underlying principles, design considerations, and advantages of this innovative technology. By integrating theoretical analysis, numerical simulations, and experimental validation, the study demonstrates the ability of these antennas to deliver high-performance radiation characteristics within the challenging THz frequency range. The proposed design holds significant promise for a wide range of applications, including high-speed wireless communication, advanced THz imaging for medical diagnostics and security scanning, precise spectroscopy for chemical analysis, and improved quality control processes across various industrial sectors.\u003c/p\u003e\n\u003cp\u003eThe distinctiveness of this research lies in its dedicated focus on the 220–325 GHz frequency range within the THz spectrum, a band that remains underrepresented in existing technologies. By leveraging all-photopolymer materials instead of traditional metallic horn antennas, this work introduces groundbreaking innovations. These advancements result in improved efficiency, enhanced miniaturization capabilities, precise radiation control, and optimized material properties tailored specifically for the challenging demands of the THz spectrum. This targeted and innovative approach paves the way for exploring new applications in high-speed communication, advanced THz imaging, precise chemical analysis, and improved quality control across diverse industries.\u003c/p\u003e\n\u003cp\u003eIn addition to their numerous advantages, these antennas exhibit material properties specifically optimized for operation within the THz frequency range. These optimizations include favorable permittivity and permeability characteristics, which significantly enhance antenna performance and establish a clear advantage over traditional metallic horn antennas. However, it is important to note that while all-photopolymer Bragg horn antennas deliver exceptional performance in the millimeter-wave (mmWave) and THz frequency ranges, their applicability at lower frequencies is inherently limited. This limitation arises from their precisely engineered design, which is tailored to the shorter wavelengths characteristic of the THz spectrum.\u003c/p\u003e"},{"header":"2. Design and Fabrication of All-Photopolymer Bragg Horn Antennas","content":"\u003ch2\u003e2.1\u0026nbsp;Design of All-Photopolymer Bragg Horn Antennas\u003c/h2\u003e\n\u003cp\u003eAll-photopolymer Bragg horn antennas, fabricated from Accura ClearVue [29],\u0026nbsp;are specialized devices designed for operation in the terahertz (THz) frequency range, specifically between 220 GHz and 325 GHz. These antennas stand out due to their non-metallic construction, which makes them highly suitable for THz applications. Their unique horn-shaped design plays a critical role in precisely controlling signal emission, facilitating their use in various advanced fields. Figure 1(a) illustrates the perspective geometry of the Bragg fiber horn antenna integrated with the horn-type adapter [29]. Within the Bragg fiber structure, the outermost layer—measuring 4.6 mm in thickness with a support bridge width of 0.64 mm—serves as a robust protective polymer layer. This layer enhances mechanical stability, provides resistance to environmental conditions, absorbs residual electromagnetic waves, and effectively shields the fiber from external interference [29].\u003c/p\u003e\n\u003cp\u003eThe horn-type adapter serves as a critical component, connecting a standard WR-3.4 waveguide to a Bragg fiber through its input aperture. It facilitates the conversion of the TE\u003csub\u003e10\u003c/sub\u003e mode from the rectangular waveguide into the fundamental HE\u003csub\u003e11\u003c/sub\u003e mode within the Bragg fiber, which is characterized by linear polarization [29]. Unlike the input mode described in [30], which corresponds to a free-space Gaussian beam, the mode in this work is a circular waveguide mode at the output aperture of the horn-type adapter. This hybrid mode consists of multiple competing components, with the fundamental TE\u003csub\u003e11\u003c/sub\u003e mode of the hollow metallic circular waveguide (HMCW) being the primary mode. Achieving proper phase matching is essential for minimizing signal loss and reflection, thereby ensuring efficient electromagnetic energy transfer between the waveguides. Effective phase matching allows seamless energy propagation from the horn-type adapter to the THz Bragg fiber, significantly enhancing measurement accuracy and reliability.\u003c/p\u003e\n\u003cp\u003eFigure 1(b) provides a cross-sectional view of the all-photopolymer Bragg horn antenna, with the key parameters of both the Bragg fiber horn and the horn-type adapter summarized in Table I. The design of the Bragg horn antenna centers on three critical parameters: the flare angle (θ), the aperture length (\u003cem\u003eA\u003csub\u003eL\u003c/sub\u003e\u003c/em\u003e), and the flare horn length (\u003cem\u003eF\u003csub\u003eL\u003c/sub\u003e\u003c/em\u003e). However, due to the interdependence between the flare angle and the aperture length, this study focuses on varying the flare angle (θ) to assess the antenna's performance. The evaluation considers the reflection coefficient (S\u003csub\u003e11\u003c/sub\u003e), radiation pattern, and realized gain of the antenna at 0°.\u003c/p\u003e\n\u003cp\u003eIn this study, the CST Studio Suite [31] was utilized to optimize the design parameters of the all-photopolymer Bragg horn antenna. The horn extension length was fixed at 100 mm to facilitate the transition of the electromagnetic field into the fundamental HE\u003csub\u003e11\u003c/sub\u003e mode within the Bragg fiber [30]. Additionally, the flare horn length (FL) was set at 50 mm to minimize insertion loss in the hollow Bragg fiber. As a result, the flare angle (θ) was identified as the primary variable for optimizing the gain performance of the Bragg fiber antenna.\u003c/p\u003e\n\u003cp\u003eFigure 2 illustrates the simulated results for varying the flare angle from 5° to 30°. As shown in Figure 2(a), the reflection coefficient (S\u003csub\u003e11\u003c/sub\u003e) across the full operating band of 220–325 GHz is slightly higher for a flare angle of 30° compared to 5° and 15°. Despite this, the antenna exhibits favorable performance, maintaining S\u003csub\u003e11\u003c/sub\u003e values below -20 dB across the entire band. Figure 2(b) presents the simulated realized gain of the Bragg fiber horn antenna at 0° for the three flare angles: 5°, 15°, and 30°. The results reveal that all configurations achieve a realized gain exceeding 20 dBi across the band, with the 5° flare angle delivering the highest performance. For the 5° configuration, the realized gain surpasses 25.3 dBi throughout the band, peaking at 29.48 dBi at 300 GHz.\u003c/p\u003e\n\u003cp\u003eFigure 3 depicts the radiation patterns at three sampling frequencies—220 GHz, 270 GHz, and 320 GHz—representing the lower, middle, and upper frequencies of the WR-3.4 band, respectively. At 220 GHz, the maximum gains achieved for the three flare angles (5°, 15°, and 30°) are 25.3 dBi, 22.0 dBi, and 20.2 dBi, with corresponding half-power beamwidths (HPBWs) of 6.7°, 10.9°, and 15.4°. At the center frequency of 270 GHz, the maximum gains for the same flare angles are 26.0 dBi, 25.2 dBi, and 22.0 dBi, with HPBWs of 5.6°, 6.3°, and 11.1°, respectively. At 320 GHz, representing the upper end of the operating band, the maximum gains for the three configurations are 29.0 dBi, 28.6 dBi, and 25.2 dBi, with corresponding HPBWs of 4.3°, 4.5°, and 5.2°.\u003c/p\u003e\n\u003cp\u003eThe simulation results for the three evaluated parameters—reflection coefficient (S\u003csub\u003e11\u003c/sub\u003e), realized gain at 0°, and radiation patterns across flare angles of 5°, 15°, and 30°—indicate that the Bragg fiber horn antenna with a 5° flare angle delivers the best overall performance under all conditions. This configuration consistently outperforms the other flare angles in terms of gain, efficiency, and beamwidth, making it the optimal choice for the studied frequency range.\u003c/p\u003e\n\u003ch2\u003e2.2 Fabrication of All-Photopolymer Bragg Horn Antennas\u003c/h2\u003e\n\u003cp\u003eThe fabrication process of the Bragg fiber horn antenna began with its design, which was meticulously developed using CST simulation software to optimize performance parameters. The finalized design was then implemented using a 3D Systems PolyJet 7000 HD 3D printer, leveraging the stereolithography technique to achieve high precision in manufacturing the all-photopolymer structure. Following this, the horn-type adapter was fabricated using CNC milling to ensure dimensional accuracy and surface quality. A copper connector was specifically flared to match the diameter of the Bragg fiber, ensuring proper alignment and minimal signal loss. The CNC milling process provided the precision necessary to meet the design specifications and facilitated seamless integration of the adapter with the Bragg fiber horn antenna. The final assembly, depicted in Figure 4, features an all-photopolymer Bragg horn antenna optimized for the 220–325 GHz frequency range. The design includes a flare angle of 5°, which was selected for its superior performance in simulations, and integrates efficiently with the horn-type adapter to enhance overall functionality.\u003c/p\u003e"},{"header":"3. Measurement Results","content":"\u003cp\u003eTo evaluate the performance of the all-photopolymer Bragg horn antenna, measurements were conducted using a Keysight Technologies PNA-X N5242 Vector Network Analyzer (VNA), equipped with two OML WR-3.4 frequency extender heads. These measurements included the reflection coefficient (S\u003csub\u003e11\u003c/sub\u003e) and radiation pattern over the 220–325 GHz frequency range. The Line-Reflect-Line (LRL) calibration technique was employed to ensure accurate and reliable data across the operating band. A laser alignment system, commonly utilized in terahertz (THz) measurements, was implemented to achieve precise alignment and controlled rotation of the antenna during testing, minimizing alignment errors and enhancing measurement accuracy. The measurement setup, illustrated in Figure 5, consists of a standard conical horn antenna connected to a WR-3.4 frequency extender acting as the transmitter (Tx) and the all-photopolymer Bragg horn antenna, integrated with a horn-type adapter and WR-3.4 frequency extender, serving as the receiver (Rx) and antenna under test (AUT). This configuration ensured a controlled and repeatable environment for assessing the antenna's performance metrics.\u003c/p\u003e\n\u003cp\u003eFigure 6 compares the measured and simulated results for the reflection coefficient (S\u003csub\u003e11\u003c/sub\u003e) across the full WR-3.4 frequency band (220–325 GHz). The data confirm that the antenna design achieves excellent performance, maintaining an S\u003csub\u003e11\u003c/sub\u003e value consistently below -20 dB across the entire band. This indicates minimal signal reflection and efficient energy transfer. The results also highlight a fractional bandwidth of approximately 38.5%, underscoring the antenna's capability to operate effectively over a broad frequency range while meeting the stringent requirements of THz applications.\u003c/p\u003e\n\u003cp\u003eThe broadband gain of the proposed all-photopolymer Bragg horn antenna was determined by recording the transmission coefficients (S\u003csub\u003e21\u003c/sub\u003e) and using them to calculate the realized gain in units of dBi. Figure 7 illustrates the comparison between the simulated and measured realized gain of the antenna across the 220–320 GHz frequency range, with data collected at 10 GHz intervals. Table II provides the detailed results, including the calculated percentage differences between the simulated and measured values. The findings indicate that the maximum error between the simulated and measured gain is within 4.28%, demonstrating the high accuracy and reliability of the measurement system employed in this study. These results validate the robustness of the design and the effectiveness of the testing methodology.\u003c/p\u003e\n\u003cp\u003eFor radiation pattern measurements, a WR-3.4 horn antenna with a nominal gain of 26 dBi and a half-power beamwidth (HPBW) of 10° was utilized as the standard reference antenna. The radiation characteristics of the all-photopolymer Bragg horn antenna were measured using a Keysight VNA equipped with frequency extender heads. Precise antenna positioning and rotation during the measurements were ensured using a laser alignment system, which minimized alignment errors and enhanced measurement accuracy. The test setup maintained a 50 mm separation between the antenna under test (AUT) and the reference antenna, a distance exceeding the simulated far-field requirement for the upper frequency of 320 GHz. The AUT was manually rotated and adjusted across a range of angles from −45° to +45°. Within the central range of −10° to +10°, 1° increments were used, while 5° increments were applied for the wider range of ±10° to ±45°. This controlled rotation ensured comprehensive angular coverage for the evaluation. The radiation pattern of the Bragg fiber horn antenna was measured at three representative frequencies—220 GHz, 270 GHz, and 320 GHz—corresponding to the lower, middle, and upper ranges of the WR-3.4 band (220–325 GHz). Figure 8 (a)–(c) illustrates the normalized comparison between the measured and simulated radiation patterns of the antenna at these frequencies, highlighting the performance and agreement between the two datasets.\u003c/p\u003e\n\u003cp\u003eThe results indicate that the radiation pattern shows a strong correlation between the simulated and measured data within the angular range of −30° to +30°. This agreement highlights the accuracy of the antenna design and measurement setup in capturing the intended performance characteristics. However, beyond ±30°, a noticeable mismatch is observed between the simulated and measured results. This discrepancy is attributed to significant free-space path loss, which reduces the dynamic range of the VNA and impacts the accuracy of measurements in these angular regions.\u003c/p\u003e\n\u003cp\u003eThe antenna design presented in this work strikes an effective balance between achieving high gain and maintaining a compact form factor, while carefully accounting for the material loss characteristics of the chosen photopolymer. Although higher realized gains could potentially be obtained using lower-loss materials such as high-resistivity silicon or GaAs, these alternatives come with significantly higher costs and require complex manufacturing processes, such as those involving advanced cleanroom facilities. In contrast, the additive manufacturing approach employed in this study, particularly the 3D-printing technique, offers a simpler, more accessible fabrication method that is well-suited for rapid prototyping and mass production at substantially reduced costs. This approach not only simplifies the production process but also aligns with the growing demand for eco-friendly and cost-effective solutions in terahertz (THz) technology. Table III provides a detailed comparison of eight key performance parameters—including structure, coupling efficiency, repeatability, user expertise requirements, fabrication and material costs, and environmental impact—between the THz antenna proposed in this work and other state-of-the-art designs reported in the literature [32]–[40].\u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThis study introduces the all-photopolymer Bragg horn antenna, specifically designed to operate within the WR-3.4 band, covering the 220–325 GHz frequency range. To evaluate its performance, three flare horn angles—5°, 15°, and 30°—were analyzed and compared based on key parameters, including the reflection coefficient (S\u003csub\u003e11\u003c/sub\u003e), realized gain, and half-power beamwidth (HPBW). To address coupling challenges resulting from the mismatch between the WR-3.4 aperture and the Bragg fiber aperture, a horn-type adapter was employed. This adapter facilitates the transition by connecting the standard WR-3.4 waveguide to the Bragg fiber input aperture, converting the TE\u003csub\u003e10\u003c/sub\u003e mode from the rectangular waveguide into the fundamental HE\u003csub\u003e11\u003c/sub\u003e mode within the Bragg fiber. Experimental results demonstrate that the all-photopolymer Bragg horn antenna achieves a fractional bandwidth of 38.5%, effectively covering the entire WR-3.4 band. The antenna exhibits a measured peak gain of approximately 28.98 dBi at 0°, a return loss better than −20 dB across the operating band, and a consistent HPBW of approximately 5° throughout the WR-3.4 frequency range.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNonchanutt Chudpooti:\u003c/strong\u003e Writing – review \u0026amp; editing, Writing – original draft, Validation, Resources, Investigation, Formal analysis, Data curation. \u003cstrong\u003eRungrat Viratikul:\u003c/strong\u003e Writing – original draft. \u003cstrong\u003eBinbin Hong:\u003c/strong\u003e Conceptualization, Project administration. \u003cstrong\u003eFeaveya Kheawprae:\u003c/strong\u003e Methodology. \u003cstrong\u003eAkkarat Boonpoonga:\u003c/strong\u003e Supervision. \u003cstrong\u003ePanuwat Janpugdee:\u003c/strong\u003e Supervision, Funding acquisition. \u003cstrong\u003eWeijia Zhan:\u003c/strong\u003e Supervision. \u003cstrong\u003ePrayoot Akkaraekthalin:\u003c/strong\u003e Supervision, Funding acquisition. \u003cstrong\u003eJoachim Oberhammer:\u003c/strong\u003e Supervision. \u003cstrong\u003eNutapong Somjiti:\u003c/strong\u003e Writing – review \u0026amp; editing, Conceptualization, Funding acquisition.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported in part by the National Natural Science Foundation of China under Grant 62105213; in part by Guangdong Basic and Applied Basic Research Fund under Grant 2020A1515111037; in part by the National Science, Research and Innovation Fund (NSRF), and King Mongkut’s University of Technology North Bangkok, under Contract KMUTNB-FF-67-A-02; in part by the Ph.D. Matching Fund granted by the Electrical Engineering Department, Chulalongkorn University; in part by the Engineering and Physical Science Research Council under Grant EP/S016813/1; and in part by the Swedish Research Council (VR) under Grant 2021-05842_VR.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData will be made available on request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eCooper, K. 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Lett.\u003c/em\u003e \u003cb\u003e56\u003c/b\u003e, 11\u0026ndash;13 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHao, Z. C. et al. Development of a low-cost THz metallic lens antenna. \u003cem\u003eIEEE Antennas. Wirel. Propag. Lett.\u003c/em\u003e \u003cb\u003e16\u003c/b\u003e, 1751\u0026ndash;1754 (2017).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1: The Key Parameters of the All-Photopolymer Bragg Horn Antennas and Horn-Type Adapter\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"552\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003eParameter\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eDescription\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003eValue\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003eA\u003csub\u003eL\u003c/sub\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eAperture length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e55.60, 73.65, 104.58 mm\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003eF\u003csub\u003eL\u003c/sub\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eFlare horn length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e50 mm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003eH\u003csub\u003eL\u003c/sub\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eHorn extension length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e100 mm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026theta;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eFlare angle\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e5, 15, 30 degrees\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003eW\u003csub\u003eL\u003c/sub\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eWR-3.4 aperture length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e3 mm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003eT\u003csub\u003eL\u003c/sub\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eTapered length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e45.3 mm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003eL\u003csub\u003e1\u003c/sub\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eHorn-type adapter length\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e53 mm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003eW\u003csub\u003e1\u003c/sub\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eHorn-type adapter width\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e50 mm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 144px;\"\u003e\n \u003cp\u003e\u003cem\u003eH\u003csub\u003e1\u003c/sub\u003e\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 210px;\"\u003e\n \u003cp\u003eHorn-type adapter height\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 198px;\"\u003e\n \u003cp\u003e50 mm\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eTable 2: The Calculated Comparison Results of Simulated and Measured Realized Gain at 0 degree\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"510\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003eFrequency (GHz)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eSimulated realized gain (dBi)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003eMeasured realized gain\u003c/p\u003e\n \u003cp\u003e(dBi)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eError\u003c/p\u003e\n \u003cp\u003e(%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e220\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e25.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e24.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e2.77\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e230\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e25.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e25.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e2.06\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e240\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e25.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e25.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e1.24\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e250\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e26.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e25.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e1.38\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e260\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e26.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e25.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e1.82\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e270\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e26.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e25.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e2.85\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e280\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e28.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e27.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e1.49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e290\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e29.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e28.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e1.38\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e29.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e28.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e1.70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e310\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e29.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e28.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e1.60\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e320\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e28.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 127px;\"\u003e\n \u003cp\u003e27.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 128px;\"\u003e\n \u003cp\u003e4.28\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eTable 3: Comparisons of Key Properties between Different THz Antennas\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"686\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRef. No.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAntenna Structure\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOperating Band\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(THz)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCoupling efficiency\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMeasurement repeatability\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOperator experience requirement\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFabrication cost\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMaterial Cost\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEco-Friendly Material\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[32]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eMulti-angle Horn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e1.7-2.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[33]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eCorrugated conical horn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e0.211-0.275\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[34]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e3D-printed back-to-back horn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e0.22-0.325\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[35]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eHemispherical lens antennas\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e0.22-0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[36]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eIntegrated an \u003cem\u003eE\u003c/em\u003e-plane flare and dual \u003cem\u003eH\u003c/em\u003e-plane reflectors\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e0.325-0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[37]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eStep-profiled corrugated\u003c/p\u003e\n \u003cp\u003ehorn antennas integrated in LTCC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e0.242-0.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[38]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003ePyramidal horn antenna\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e0.191\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[39]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eCircularly polarized antennas\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e0.22-0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e[40]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003eMetallic lens antenna\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e0.37-0.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eMedium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003eRepeatable\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003eLow\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003eHigh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003eNon-biodegradable\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 54px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eThis work\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 128px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eAll-photopolymer\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e\u003cem\u003eBragg Horn Antenna\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003e0.22-0.325\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eHigh\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 77px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eHighly Repeatable\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 74px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eLow\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 69px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eLow\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 58px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eLow\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 98px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eBiodegradable\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"All-photopolymer horn antenna, Bragg structure, THz antennas","lastPublishedDoi":"10.21203/rs.3.rs-6221054/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6221054/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis paper presents the development of the world\u0026rsquo;s first high-gain, all-photopolymer Bragg horn antennas explicitly designed for the WR-3.4 band (220\u0026ndash;325GHz), marking a groundbreaking advancement in terahertz (THz) antenna technology. Unlike conventional metallic horn antennas, which suffer from conductor losses and manufacturing complexity, this innovative design utilizes eco-friendly photopolymer materials and additive manufacturing, achieving a fractional bandwidth of 38.5% that fully covers the WR-3.4 band. The proposed antenna achieves a measured peak gain of 28.98 dBi at 300GHz, with a return loss better than \u0026minus;\u0026thinsp;20dB across the band and a consistent half-power beamwidth (HPBW) of ~\u0026thinsp;5\u0026deg;, ensuring precise directivity and minimal sidelobe interference. By employing a novel horn-type adapter for seamless mode conversion from TE\u003csub\u003e10\u003c/sub\u003e to the fundamental HE\u003csub\u003e11\u003c/sub\u003e mode, the design significantly enhances coupling efficiency and reduces signal loss. Additionally, fabrication costs can be reduced by over 50% compared to traditional metallic designs, while maintaining repeatability and enabling rapid prototyping. As the first demonstration of photopolymer-based antennas achieving such high gains in the 220-325GHz THz spectrum, this work establishes a new benchmark in THz antenna technology, providing an eco-friendly, cost-effective, and high-performance solution for high-speed communication, medical diagnostics, security imaging, and spectroscopy applications.\u003c/p\u003e","manuscriptTitle":"220–325GHz All-Photopolymer Bragg Horn Antennas Towards Eco-Friendly Terahertz Applications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-21 10:05:08","doi":"10.21203/rs.3.rs-6221054/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-05-05T19:00:53+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-23T16:54:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-19T10:23:25+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-09T13:38:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"201901496583860795751734010548915850321","date":"2025-04-04T12:11:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"55616666981416706366945469404857251341","date":"2025-04-04T10:12:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"146189829207106666677318383379653753623","date":"2025-04-03T07:52:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"46218996755558887760001174883070519945","date":"2025-03-31T21:04:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"156759084994259322194002188858779407608","date":"2025-03-30T11:17:36+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-03-30T08:14:29+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-03-26T15:41:05+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-03-26T15:05:03+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-26T14:46:07+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-03-26T14:40:39+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f67cd956-8247-44a9-820e-11ecc7ead849","owner":[],"postedDate":"April 21st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":46917657,"name":"Physical sciences/Engineering"},{"id":46917658,"name":"Physical sciences/Engineering/Electrical and electronic engineering"}],"tags":[],"updatedAt":"2025-08-04T16:40:19+00:00","versionOfRecord":{"articleIdentity":"rs-6221054","link":"https://doi.org/10.1038/s41598-025-11978-9","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-07-30 16:20:59","publishedOnDateReadable":"July 30th, 2025"},"versionCreatedAt":"2025-04-21 10:05:08","video":"","vorDoi":"10.1038/s41598-025-11978-9","vorDoiUrl":"https://doi.org/10.1038/s41598-025-11978-9","workflowStages":[]},"version":"v1","identity":"rs-6221054","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6221054","identity":"rs-6221054","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}