A miniature Fourier transform spectrometer based on an electrothermal MEMS mirror with asynchronous calibration

In a MEMS mirror-based dual interference Fourier transform spectrometer (FTS) with a laser interferometer as the position sensing mechanism, making the two interferometers coaxial is very challenging. To solve this problem, a single interference MEMS FTS based on asynchronous calibration is designed. This single interference FTS uses a dichroic mirror to couple a laser beam and a broadband light beam into the same interferometer. Since the two optical beams share the same optical path, they will experience the same change when the position of any optical component along the optical path is adjusted. In data acquisition, the two interference signals are acquired asynchronously by the same InGaAs photodetector. This asynchronous calibration can effectively eliminate the laser coupling issue. According to the experimental results, compared with the dual interference spectrometer, the proposed spectrometer based on asynchronous calibration can improve the spectral repeatability and make the system simpler and lower power consumption.