Picture of neon light reading 'Open'

Discover open research at Strathprints as part of International Open Access Week!

23-29 October 2017 is International Open Access Week. The Strathprints institutional repository is a digital archive of Open Access research outputs, all produced by University of Strathclyde researchers.

Explore recent world leading Open Access research content this Open Access Week from across Strathclyde's many research active faculties: Engineering, Science, Humanities, Arts & Social Sciences and Strathclyde Business School.

Explore all Strathclyde Open Access research outputs...

Recovery of absorption line shapes with correction for the wavelength modulation characteristics of DFB lasers

Benoy, Thomas and Lengden, Michael and Stewart, George and Johnstone, Walter (2016) Recovery of absorption line shapes with correction for the wavelength modulation characteristics of DFB lasers. IEEE Photonics Journal, 8 (3). ISSN 1943-0655

[img]
Preview
Text (Benoy-etal-IEEEPF2016-recovery-of-absorption-line-shapes-with-correction-for-the-wavelength)
Benoy_etal_IEEEPF2016_recovery_of_absorption_line_shapes_with_correction_for_the_wavelength.pdf - Final Published Version
License: Creative Commons Attribution 4.0 logo

Download (1MB) | Preview

Abstract

Tunable diode laser spectroscopy combined with wavelength modulation spectroscopy (WMS) is an important technique for non-invasive measurements of gas parameters such as pressure, concentration and temperature in high noise, harsh environments. A variety of laser types are used for these applications and the modulation characteristics can have significant effects on line shape recovery. Here we identify important characteristics of distributed feedback (DFB) lasers that need to be taken into account in the context of WMS and illustrate the effects with a 2μm wavelength, multi quantum well DFB laser used for CO2 detection. The modulation response of the laser is measured and we demonstrate how the phasor decomposition method (PDM) may be used to obtain accurate line shapes from first harmonic WMS signals by correcting for phase variation across the laser’s low frequency current sweep. We also demonstrate how the PDM approach can be improved by removing the need to pre-set the orientation of the lock-in axis, to isolate the residual amplitude modulation(RAM)component, making it more suitable for field applications.