Logarithmic conversion of absorption detection in wavelength modulation spectroscopy with a current-modulated diode laser.
Logarithmic-conversion data processing used in wavelength modulation spectroscopy (WMS) with a current-modulated diode laser as its source is analyzed and compared with second-to-first ratio detection. Analytic Fourier coefficients of logarithmic-converted residual amplitude modulation (RAM) of a light source are given. An experimental setup for methane absorption detection at 1650 nm is described. It is shown theoretically and experimentally that logarithmic-converted WMS cannot only eliminate the fluctuation of received light power, but also improve the signal-to-noise ratio significantly.
Wang
Yuntao
Y
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800, China. fica@163.com
Cai
Haiwen
H
Geng
Jianxin
J
Fang
Zujie
Z