Parameter-tuning stochastic resonance as a tool to enhance wavelength modulation spectroscopy using a dense overlapped spot pattern multi-pass cell

The parameter-tuning stochastic resonance (SR) method can convert part of the noise energy into the signal energy to suppress the noise and amplify the signal, comparing with traditional weak periodic signal detection methods (e.g., time average method, filtering method, and correlation analysis method). In this work, the numerical calculation is conducted to find the optimal resonance parameters for applying the SR method to the wavelength modulation spectroscopy (WMS). Under the stochastic resonance state, the peak value of 2f signal (a constant concentration of CH4 similar to 20 ppm) is effectively amplified to similar to 0.0863V, which is 3.8 times as much as the peak value of 4000-time average signal (similar to 0.0231 V). Although the standard deviation also increases from similar to 0.0015 V(1 sigma) to similar to 0.003 V(1 sigma), the SNR can be improved by 1.83 times (from similar to 25.9 to similar to 15.8) correspondingly. A linear spectral response of SR 2f signal peak value to raw 2f signal peak value is obtained. It suggests that the SR method is effective for enhancing photoelectric signal under strong noise background. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement