Research On Tunable Spatial Heterodyne Spectroscopy With Grating-Mirror Structure

Spatial Heterodyne Spectroscopy(SHS) technology, which is an interferometric spectrum analysis technology, has the capability of very high spectral resolution and also has the characteristics of high light flux, high S/N ratio. It combines the advantages of grating dispersion and Fourier-transform spectroscopy(FTS) techniques. In the study of faint, extended sources at high resolving power, Spatial Heterodyne Spectroscopy(SHS) offers significant etendue advantages relative to conventional dispersive grating spectrometers. The sampled bandpass of SHS is limited by the highest spatial frequency that can be sampled by the detector, which is typically less than 10 nm.This limitation has made these instruments useful primarily for studies of single emission line features or molecular bands, but restricted its wider application range. The research of broadband Spatial Heterodyne Spectroscopy has been paid attention abroad, but has little research in China.The common way to widen the spectral coverage of Spatial Heterodyne Spectrometer has a high requirement for the grating(echelle grating or symmetrically ruled grating), and the Spatial Heterodyne Spectrometer with the echelle grating has the problems of separating multi-dispersion orders and the algorithm of the recover spectrum.Aiming at the shortcomings of the narrow bandpass of Spatial Heterodyne Spectroscopy, a tunable SHS with Grating-Mirror structure is designed in this paper. The spectral coverage is widened to a much broader spectral range by rotating grating, and the mirror is slightly tilted to ensure the monodromy of the recover spectra. The feasibility of this design to expand the bandpass is proved. By increasing the rotated times of the grating and introducing methods to eliminate stray light etc, the bandpass will be expanded farther and the spectral resolution will be higher. The chief research work on the instrument is as following.Firstly, a tunable SHS with Grating-Mirror structure is designed. In order to widen the application field of the spectrometer, the spectral coverage is widened to a much broader spectral range by rotating grating, and the mirror is slightly tilted to ensure the monodromy of the recover spectra.Secondly, the parameters of tunable Spatial Heterodyne Spectroscopy with Grating-Mirror structure are designed. The parameters of Spatial Heterodyne Spectroscopy mainly include spectral resolution and spectral range, which depend on the selection of structure parameters such as grating, detector and so on.Thirdly, simulation and error analysis of the tunable Spatial Heterodyne Spectroscopy with the Grating- Mirror structure. The feasibility of this design to expand the bandpass is proved by ZEMAX and the influence of error on the performance of the instrument has been discussed.Fourthly, we build the prototype on optical platform in the laboratory, the experiment result shows that the designed SHS structure has the bandpass range up to about 100 nm and its spectral resolution is better than 0.29 nm. The feasibility of this design to expand the bandpass is proved. By increasing the rotated times of the grating and introducing methods to eliminate stray light etc, the bandpass will be expanded farther and the spectral resolution will be higher.