Study on convex grating in hyperspectral imaging spectrometers

Abstract

The convex grating is one of the key elements in Offner hyperspectral imaging spectrometers. In this paper the design of the holographic convex grating focuses on the optimization of its recording parameters for aberration correction. Meantime, the diffraction efficiency of the convex grating is discussed by using rigorous coupled-wave theory. The results show: within the wavelength range from 0.4μm to 0.78μm, the diffraction efficiency can be over 20% and up to 40% through controlling the groove depth and duty cycle of rectangular grating; the diffraction efficiency can be over 35% through controlling the blaze degree of the blazed grating. The rectangular surface-relief convex grating with the period of 5μm in the center, and the ruled area - a convex with its radius 100mm and aperture 40mm has been fabricated by holographic-ion beam etching. A prototype blazed convex grating will be fabricated in late 2010.