Design and Testing of Cavity Decay Spectroscopy Photodetector

CRDS is a spectroscopy method widely used for trace gas detection. It can be used to measure the trace component detection of insulation gas decomposition in power systems, providing a reliable guarantee for the safe operation of power systems. And the photodetector is a very critical part of the CRDS. For the requirements of low noise, high bandwidth and fast response of cavity decay spectra, an InGaAs photodiode and a low-noise operational amplifier were selected to design a photodetector with a response wavelength range of 800-1700 nm. The photodetector has an amplification of 10M, a response bandwidth of 1 MHz, a noise level of less than 0.1 mV, and a minimum detectable light intensity of 20 nW. The FFT analysis and sensitivity check of the output signal are performed through simulation, and the results show that the distortion rate can reach 0.0001. In the optical cavity decay signal detection platform, the signal collected by the photoelectric detector was processed to obtain the fitted curves of absorption spectral lines and decay time of the cavity, and the absorption peaks of the decay curve and fine sweep spectrogram were verified, and the detector can be used for gas concentration analysis of CRDS equipment.