Analysis and Optimization of Order Overlap in Echelle Imaging Spectrometers

In the currently deployed scheme utilizing Acousto-Optic Tunable Filter (AOTF) in conjunction with the echelle grating, the maximum spectral overlap for low diffraction orders exceeds 2/3, while encountering the issue of spectral discontinuity at higher diffraction orders. We propose a method to address the issue of image plane order overlap in echelle imaging spectrometers. This method utilizes the principle of matching the spectral resolution of the AOTF with the free spectral range of the echelle to eliminate order overlap, while ensuring that there are no gaps between the spectral bands in each output. With this method, we recalculate the spectral bands corresponding to the orders of the echelle and make enhancements to the imaging spectrometer based on the calculation results. The results of the design show that the improved imaging spectrometer has excellent imaging quality, validating the effectiveness and practicality of this method.