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[Editor's Pick] Current Optics and Photonics Vol. 6 no. 3 (2022 June)

사무국 hit 273 date 2022-06-24

Spectral Reconstruction for High Spectral Resolution in a Static Modulated Fourier-transform Spectrometer

Ju Yong Cho1, Seunghoon Lee2, Hyoungjin Kim1, and Won Kweon Jang1*

 

Current Optics and Photonics  Vol. 6 No. 3 (2022 June) pp. 244-251
DOI: https://doi.org/10.3807/COPP.2022.6.3.244

 

  Fig. 1  The static modulated Fourier-transform spectrometer during the reconstruction process and a magnified optical layout for its optical-path difference. (a) Schematic view of the static modulated Fourier-transform spectrometer consisting of a modified Sagnac interferometer. S, source; SD, source driver; M1, fixed mirror; M2, displaced mirror; BS, beam splitter; FL, focusing lens; D, onedimensional detector; CI, computer interface; SI, sample interferogram; TM, transfer-function matrix of the spectrometer; RS, reconstructed spectrum. (b) Magnified optical layout near the one-dimensional detector array.

 

Keywords: Interferometer, Reconstruction, Spectrometry, Static modulation
OCIS codes: (000.4430) Numerical approximation and analysis; (070.4790) Spectrum analysis;(120.3180) Interferometry; (300.6300) Spectroscopy, Fourier transforms


Abstract
We introduce a spectral reconstruction method to enhance the spectral resolution in a static modulated Fourier-transform spectrometer. The optical-path difference and the interferogram in the focal plane, as well as the relationship of the interferogram and the spectrum, are discussed. Additionally, for better spectral reconstruction, applications of phase-error correction and apodization are considered. As a result, the transfer function of the spectrometer is calculated, and then the spectrum is reconstructed based on the relationship between the transfer function and the interferogram. The spectrometer comprises a modified Sagnac interferometer. The spectral reconstruction is conducted with a source with central wave number of 6,451 cm−1 and spectral width of 337 cm−1. In a conventional Fourier-transform method the best spectral resolution is 27 cm−1, but by means of the spectral reconstruction method the spectral resolution improved to 8.7 cm−1, without changing the interferometric structure. Compared to a conventional Fourier-transform method, the spectral width in the reconstructed spectrum is narrower by 20 cm−1, and closer to the reference spectrum. The proposed method allows high performance for static modulated Fourier-transform spectrometers.