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 0030-4018Full text not available in this repository. (Request a copy from the Strathclyde author)
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.
|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|
|Depositing user:||Dr Graham Thursby|
|Date Deposited:||15 Oct 2010 10:58|
|Last modified:||22 Mar 2017 11:06|