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Elimination of residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy using an optical fiber delay line

Chakraborty, Arup Lal and Ruxton, Keith C. and Johnstone, W. and Lengden, Michael and Duffin, K. (2009) Elimination of residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy using an optical fiber delay line. Optics Express, 17 (12). pp. 9602-9607. ISSN 1094-4087

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Abstract

A new fiber-optic technique to eliminate residual amplitude modulation in tunable diode laser wavelength modulation spectroscopy is presented. The modulated laser output is split to pass in parallel through the gas measurement cell and an optical fiber delay line, with the modulation frequency / delay chosen to introduce a relative phase shift of pi between them. The two signals are balanced using a variable attenuator and recombined through a fiber coupler. In the absence of gas, the direct laser intensity modulation cancels, thereby eliminating the high background. The presence of gas induces a concentration-dependent imbalance at the coupler's output from which the absolute absorption profile is directly recovered with high accuracy using 1f detection.

Item type: Article
ID code: 14762
Keywords: pressure, temperature, frequency, gases, Electrical engineering. Electronics Nuclear engineering, Physics
Subjects: Technology > Electrical engineering. Electronics Nuclear engineering
Science > Physics
Department: Faculty of Engineering > Electronic and Electrical Engineering
Related URLs:
    Depositing user: Strathprints Administrator
    Date Deposited: 16 Jun 2010 15:02
    Last modified: 12 Mar 2013 11:49
    URI: http://strathprints.strath.ac.uk/id/eprint/14762

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