An efficient and aberration-free off-plane grating spectrometer and monochromator for EUV – soft X-ray applications

Abstract We demonstrate a novel dual-optic imaging EUV-X-ray spectrometer and monochromator that attains an unprecedented throughput efficiency exceeding 60% theoretically, along with a superior spectral resolution of λ/Δλ>200. Exploiting the benefits of the conical diffraction geometry, the optical system is globally optimized in multidimensional parameter space to guarantee optimal imaging performance over a broad spectral range while maintaining circular and elliptical polarization states at the first, second, and third diffraction orders. Moreover, our analysis indicates minimal temporal dispersion, with pulse broadening confined within 80 fs, which enables ultrafast spectroscopic and pump-probe measurements with femtosecond accuracy. Furthermore, the spectrometer can be effortlessly transformed into a monochromator spanning the EUV–soft X-ray spectral region. Such capability allows coherent diffractive imaging applications to be conducted with highly monochromatic light in a broad spectral range and extended to the soft X-ray region with minimal photon loss. Thus, enhancing the imaging resolution and enabling the investigation of bio and nano samples. In addition, the advanced design incorporates optimized spatio-temporal parameters, facilitating cutting-edge versatile EUV - X-ray applications.