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Absorption line profile recovery based on residual amplitude modulation and first harmonic integration methods in photoacoustic gas sensing

Li, Li and Arsad, Norhana and Stewart, G. and Thursby, G.J. and Culshaw, B. and Wang, Yiding (2011) Absorption line profile recovery based on residual amplitude modulation and first harmonic integration methods in photoacoustic gas sensing. Optics Communications, 284 (1). pp. 312-316. ISSN 0030-4018

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Abstract

Two methods for recovery of gas absorption line profiles are presented in this paper using photoacoustic spectroscopy and tunable diode laser spectroscopy (TDLS) with wavelength modulation (WM). A theoretical analysis based on Fourier coefficients is given in order to describe the various components that arise under simultaneous intensity and frequency modulation. The first method makes use of the residual amplitude modulation (RAM) signal which is always present in current modulation of distributed feedback (DFB) tunable diode lasers. The second method involves integration of a near-pure first harmonic derivative signal, separated from other distorting components by appropriate choice of the lock-in detection phase in the case of low modulation index. Good agreement is obtained with both methods between the experimental results and the theoretical simulation for the P17 absorption line of acetylene at 1535.39 nm but the second method gives a much improved accuracy and signal-to-noise ratio in lineshape recovery with photoacoustic spectroscopy.

Item type: Article
ID code: 27790
Keywords: tunable diode, laser spectroscopy, wavelength modulation, absorption line profile recovery, residual amplitude modulation, first harmonic integration, Electrical engineering. Electronics Nuclear engineering, Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering
Subjects: Technology > Electrical engineering. Electronics Nuclear engineering
Department: Faculty of Engineering > Electronic and Electrical Engineering
Related URLs:
Depositing user: Dr Graham Thursby
Date Deposited: 15 Oct 2010 11:58
Last modified: 27 Mar 2014 08:57
URI: http://strathprints.strath.ac.uk/id/eprint/27790

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