Fabrication of silver helix microstructures in a large area

The fabrication of metamaterials working in the wavelength region from visible to infrared is very attractive for beam treatment toward negative refraction and beyond the diffraction limit. The two photon absorption direct laser writing (TPA-DLW) method is a powerful tool to fabricate metamaterials with compact, dense, intricate, and periodic microstructures on the micrometer and submicrometer scales and is sensitive in the wavelength region from visible to infrared. In this study, large-area helix microstructures intended for metamaterials were fabricated using a negative photoresist, SU-8. To stabilize the fabricated free-standing helix microstructures with a 1 µm radius, circular foundations with a radius of 1.3 µm and elevation angle of 10, 12, or 14 ° were built in advance. The foundation is useful to avoid collapsing the helix microstructures. Due to the useful foundation, over 18,000 helical structures were fabricated in a large area. The obtained helical structures have the potential for metamaterials to control the handedness of a circularly polarized infrared beam.