Design and measurement of convex grating in conical diffraction Offner spectrometer

摘要

Offner spectrometer is widely applied in hyperspectral imaging spectrometers, in which the design, fabrication, and testing of convex gratings are crucial to ensure the spectral and imaging performance of the whole system. A conical diffraction Offner spectrometer is proposed with the spectral range of 400 to 900 nm, spectral resolution of 5 nm, slit length of 1 mm, and spectral dispersive width of 10 mm. A finite-element analysis is adopted to optimize the groove parameters of the conical diffraction blazed convex grating that is used in the aforesaid spectrometer. Holographic scan ion beam etching method is employed to fabricate such convex grating. Experimental facilities for testing the diffraction efficiency are built in the lab, showing that the efficiency is higher than 50% in the whole waveband and the peak efficiency is over 75%, which is consistent with the design result. The result indicates that it is feasible to design and optimize the grating groove using the finite-element analysis method.