Reconstruction and fitting of second-harmonic signals by wavelength modulation spectroscopy method based on fast Fourier transform

Linquan Lai; Yue Chen; Kongtao Chen; Jiale Tang; Kaiwen Yin; Fuqiang Jia; Dun Qiao; Yuanlong Fan; Kang Li; Nigel Copner

doi:10.3788/COL202220.093001

Chinese Optics Letters, Volume. 20, Issue 9, 093001(2022)

Reconstruction and fitting of second-harmonic signals by wavelength modulation spectroscopy method based on fast Fourier transform

Linquan Lai¹, Yue Chen¹, Kongtao Chen¹, Jiale Tang¹, Kaiwen Yin¹, Fuqiang Jia^1,*, Dun Qiao², Yuanlong Fan², Kang Li², and Nigel Copner²

Author Affiliations

¹Fujian Key Laboratory of Ultrafast Laser Technology and Applications, School of Electronic Science and Technology, Xiamen University, Xiamen 361005, China

²Wireless & Optoelectronics Research & Innovation Centre, Faculty of Computing, Engineering & Science, University of South Wales, Wales CF37 1DL, UK

show less

Abstract Get PDF View Full Text

Figures&Tables (5)

Equations (8)

References &Cited By (0)

Tools

Paper Information

Topics

Conventional wavelength modulation spectroscopy (WMS) is vulnerable to the influence of low-frequency noise. Accuracy of the method highly depends on the performance of the costly lock-in amplifier. In this article, we report a new and effective method for reconstructing second-harmonic signals through WMS based on fast Fourier transform (FFT). This method is less disturbed by low-frequency noise because it does not use a low-frequency ramp wave. Formulation and detection procedures were presented. The discrete second-harmonic waveform can be obtained by continuously changing the DC signal and FFT analysis in this method. Second-harmonic waveforms acquired by the two means are generally consistent. The experimental study validates the obtained gas concentration from 5% to 30%, showing a good linear relationship by the proposed method. The maximum relative error on concentration extraction is 2.87%; as for conventional WMS, this value is 4.50%. The developed measurement method may have potential in computed tomography.

Keywords

fast Fourier transform second-harmonic waveform wavelength modulation spectroscopy

1. Introduction

The progress of laser and spectroscopy technology has greatly promoted the development of material detection technology^[1,2]. Among them, tunable diode laser absorption spectroscopy (TDLAS) has been widely employed in gas detection across the energy, petrochemical, and mining industries because of its non-intrusiveness and high accuracy^[3–8]. It is developed into two major approaches: direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS). WMS has high sensitivity and signal-to-noise ratio (SNR) through harmonic detection. Numerous measurement results have shown that WMS is more sensitive by one to two orders of magnitude than DAS^[9].

Tools

Get Citation

Copy Citation Text

Linquan Lai, Yue Chen, Kongtao Chen, Jiale Tang, Kaiwen Yin, Fuqiang Jia, Dun Qiao, Yuanlong Fan, Kang Li, Nigel Copner. Reconstruction and fitting of second-harmonic signals by wavelength modulation spectroscopy method based on fast Fourier transform[J]. Chinese Optics Letters, 2022, 20(9): 093001

Download Citation

EndNote(RIS)BibTex Plain Text

Set citation alerts for article

Save article for my favorites