[1] Fan Fengying, Song Zengyun. Mesurement of CO2 concentration with tunable diode laser absorption spectroscopy near 2 μm [J]. Chinese J Lasers, 2012, 39(2): 0215002.

[2] Wang Guishi, Cai Tingdong,Wang Lei, et al.. Application of digital frequency locking techniques in real-time measurement of methane in atmosphere [J]. Chinese J Lasers, 2011, 38(10): 1008002.

[3] Kan Ruifeng, Liu Wenqing, Zhang Yunjun, et al.. Infrared absorption spectrometer of monitoring ambient methane [J]. Acta Optica Sinica, 2006, 26(1): 67-70.

[4] Xia Hua, Dong Fengzhong,Tu Guojie, et al.. Sensitive detection of carbon monoxide based on novel multi pass cell [J]. Acta Optica Sinica, 2010, 30(9): 2596-2601.

[5] Gao Nan, Du Zhenhui, Qi Rubin, et al.. Data preprocessing of broad-spectrum tunable-diode-laser absorption spectroscopy [J]. Acta Optica Sinica, 2012, 32(4): 0430004.

[6] A M Russel, D A Torchia. Harmonic analysis in systems using phase sensitive detectors[J]. Sci Instrum, 1962, 33(4): 442-444.

[7] R Arndt. Analytical line shapes for Lorentzian signals broad ened by modulation [J]. Appl Phys, 1965, 36(8): 2522-2524.

[8] Pawel Kluczynski, Ove Axner. Theoretical description based on Fourier analysis of wavelength-modulation spectrometry in terms of analytical and background signals [J]. Appl Opt, 1999, 38(27): 5803-5815.

[9] S Schilt, L Thevenaz, P Robert. Wavelength modulation spectroscopy: combined frequency and intensity laser modulation [J]. Appl Opt, 2003, 42(33): 6728-6738.

[10] K Ruxtona, A L Chakrabortya, W Johnstonea. Tunable diode laser spectroscopy with wavelength modulation: elimination of residual amplitude modulation in a phasor decomposition approach [J]. Sens Actuators B, 2010, 150(1): 367-375.

[11] Andrew J McGettrick, Walter Johnstone, Robert Cunningham, et al.. Tunable diode laser spectroscopy with wavelength modulation: calibration-free measurement of gas compositions at elevated temperatures and varying pressure [J]. J Lightwave Technol, 2009, 27(15): 3150-3161.

[12] Kevin Duffin, Andrew James McGettrick, Walter Johnstone, et al.. Tunable diode-laser spectroscopy with wavelength modulation: a calibration-free approach to the recovery of absolute gas absorption line shapes [J]. J Lightwave Technol, 2007, 25(10): 3114-3125.

[13] Bao Weiyi, Zhu Yong, Chen Jun, et al.. Signal analysis and spectrum distortion correction for tunable diode laser absorption spectroscopy system [J]. Spectroscopy and Spectral Analysis, 2011, 31(4): 1015-1019.

[14] Gao Nan, Du Zhenhui, Tang Mao, et al.. System parameters selection and optimization of tunable diode laser absorption spectroscopy [J]. Spectroscopy and Spectral Analysis, 2010, 30(12): 3174-3178.

[15] Zhang Rui, Zhao Xuehong, Hu Yajun, et al.. Background elimination method based on harmonic detection in no absorption spectral region [J]. Acta Optica Sinica, 2013, 33(4): 0430006.

[16] Hejie Li, Gregory B Rieker, Xiang Liu, et al.. Extension of wavelength-modulation spectroscopy to large modulation depth for diode laser absorption measurements in high-pressure gases [J]. Appl Phys, 2006, 45(5): 1052-1061.

[17] Arup Lal Chakraborty, Keith Ruxton, Walter Johnstone. Suppression of intensity modulation contributions to signals in second harmonic wavelength modulation spectroscopy [J]. Opt Lett, 2010, 35(14): 2400-2402.

[18] Pawel Kluczynski, Jorgen Gustafsson, Asa M Lindberg, et al.. Wavelength modulation absorption spectrometry an extensive scrutiny of the generation of signals [J]. Spectrochimica Acta Part B: Atomic Spectroscopy, 2001, 56(8): 1277-1354.

[19] Masaaki Imai, Koji Kawakita. Measurement of direct frequency modulation characteristics of laser diodes by Michelson interferometry [J]. Appl Phys, 1990, 29(3): 384-353.