The convex grating with high efficiency for Hyperspectral Remote Sensing

The convex grating is one of the key elements in Offner imaging spectrometers. In this paper the diffraction efficiency of the convex grating is investigated by using rigorous coupled-wave analysis (RCWA), which indicates that within the visible and near infrared broadband, the first-order diffraction efficiency can be over 40% through controlling the blaze angle of blazed convex grating. The blazed convex grating with the period of 6.17 mu m in the center, the blaze angle about 2.9 degree, the antiblaze angle about 21 degree, and the ruled area - a convex substrate with its radius 36.31mm and aperture 23.6mm has been fabricated by holographic lithography -scan ion beam etching. Experimental measurements show that the first-order diffraction efficiency is more than 30%, and the first-order diffraction efficiency at blazed wavelength can reach 62%.