Research and Optimization of Groove Distribution for Variable Line-Space (VLS) Gratings in Non-Vacuum Ultraviolet Spectral Imaging

Ultraviolet remote sensing systems generally encounter the technical limitation of insufficient effective signal energy. Optical systems featuring a lightweight and compact layout are emerging as the mainstream research and development trend in this field. Varied-line-space (VLS) gratings can simultaneously achieve effective aberration correction and beam focusing in ultraviolet spectral imaging systems, enabling fewer system components and a simplified optical layout. On this basis, the modulation mechanisms of the groove distribution of planar VLS gratings for aberration correction and dispersion manipulation in the non-vacuum ultraviolet (non-VUV) band are thoroughly investigated. We elaborate on the theories concerning the line density function of VLS gratings based on phase distribution, and implement global optimization for the parameters of holographic gratings. The overall optical performance of the grating system is evaluated via ray tracing, which verifies the capability of VLS gratings to improve spectral resolution. We further perform optical design, device fabrication, and experimental validation using VLS gratings with a central groove density of 300 lp/mm. A spectral resolution of 0.345 nm is finally realized at the central wavelength of 300 nm. This work not only enriches the fundamental theories of VLS grating systems but also demonstrates that VLS gratings can significantly boost the aberration correction performance of ultraviolet spectrometers while adopting only a small number of optical elements. The theoretical conclusions are validated by measured data, and a complementary research framework integrating theoretical analysis and experimental testing is established. This study offers novel design ideas for hyperspectral and high-spatial-resolution spectral imaging systems.