Visible Fourier Transform Spectrometer Based on Double Beam-Folding Interferometers

A Visible Fourier Transform Spectrometer(FTS) based on double beam-folding interferometers is reported. The FTS comprises two back-to-back interferometers, that share the same translation stage, used for position tracking and spectral measurement of the measured light. Therefore, the change of the optical path difference (OPD) of the position-tracking interferometer is always synchronous to that of the measured light interferometer during the scanning process. The beam folding technique is used in both interferometers. The position tracking interferometer is 4-fold, while the measured light interfeormeter is 2-fold, thus the FTS can cover the visible range. The advantage of double beam-folding setup is the reduced demand for translation range, that makes the FTS more compact. We have demonstrated a Visible FTS with a standard quality ball-bearing translation stage, and a He-Ne laser and a S60 lamp were used the light source to evaluates the FTS. It achieved a resolution of ~0.5 cm^-1 and a peak position deviation of 0.24 cm^-1 at the He-Ne laser wavelength when the scan distance reaches the travel distance of over 1 cm. This was achieved without the need for elaborate optics, sophisticated detecting electronics and high precision servo motion control. The optical components used in the detecting system limit the spectral range to 350nm-1.1μm. High quality translation stage should be used in order to achieve higher instrumental spectral resolutions.