Optimum design of a holographic parallel flat-field grating

摘要

To widen the working waveband, a new holographic parallel flat-field grating (HPFG) with two sub-gratings lying parallel on the same substrate is designed. Grating parameters of the two gratings, one for 2～5 nm and the other for 5～30 nm, are optimized based on the aberration theory of concave grating. The radius tolerances of curvature of the substrate are also analyzed. Ray-traced spectral images indicate that errors cased by ± 1 % deviation of radius can be offset by shifting the detector position within 2.5 mm. Finally, we analyze the spectral image-focusing properties. Theoretical spectral resolution of this new HPFG is pretty much the same as that of existing holographic flat-field grating. The simulation results demonstrate that our work probably can be used in the compact spectrometers with a broad spectral region and moderately high resolution.