Theoretical analysis of saturated spectral line shape of noise immune cavity enhanced optical heterodyne molecular spectroscopy

• Published in: Guang pu xue yu guang pu fen xi Vol. 34; no. 8; p. 2180
• Main Authors: Ma, Wei-guang, Tan, Wei, Zhao, Gang, Li, Zhi-xin, Fu, Xiao-fang, Dong, Lei, Zhang, Lei, Yin, Wang-bao, Jia, Suo-tang
• Format: Journal Article
• Language: Chinese
• Published: China 01.08.2014
• ISSN: 1000-0593
• DOI: 10.3964/j.issn.1000-0593(2014)08-2180-05

In the present paper a theoretical description of the line shapes of frequency modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) under saturated conditions is presented. Expressions for both Doppler broadened and Doppler free frequency modulated NICE-OHMS signals at their absorption and dispersion phases are given. The modulation frequency, saturation parameter and frequency modulation index are set to 384 MHz, 10 and 0.2, respectively in the simulation. Based on the simulated line shape curves, in the absorption detection phase there are four sub Doppler structures existing in the spectral envelope of absorption signals of two sidebands, and in the dispersion phase there are five sub-Doppler structures existing in the spectral envelope of dispersion signals of carrier and two sidebands. The sub-Doppler structure originates from the fact that two counter propagating waves interact with the same group of molecules and one can act as a detecting beam and the other can