Optimum design of a flat-field micro-spectrometer

In this paper a flat-field micro-spectrometer is designed by using varied-pitch gratings. The geometrical parameters which affect the focal curve, i.e. the radius of curvature, pitch variation, incidence angle, and the position of the focal plane, are analyzed. Then a planar concave grating is optimized by the Simulated Annealing Algorithm. The spectral region covers 400-800nm and the Linear dispersion is about 6 mum/nm. The obtained linearity of the focal curve is better than 98%. Furthermore, to get better aberration, the concave grating with arbitrary grating pro-file is also discussed.