Theoretical and Experimental Study of Heterodyne Phase-Sensitive Dispersion Spectroscopy with an Injection-Current-Modulated Quantum Cascade Laser

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

3 Scopus Citations
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Detail(s)

Original languageEnglish
Article number6176
Number of pages9
Journal / PublicationSensors (Switzerland)
Volume20
Issue number21
Online published29 Oct 2020
Publication statusPublished - Nov 2020

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Abstract

We report the theoretical and experimental study of calibration-free heterodyne phase-sensitive dispersion spectroscopy (HPSDS) in the mid-infrared using a direct current modulated mid-infrared quantum cascade laser (QCL). The modulation of QCL current at several hundred MHz or higher generates the synchronous frequency and intensity modulation of the QCL emission. An analytical model of the phase of the beat note signal in HPSDS is derived by considering the absorption and dispersion processes and incorporating the QCL modulation parameters. In the experiment, a 4.5 μm QCL modulated at 350 MHz was used to measure N2O at 200 Torr in a 10 cm gas cell. The N2O concentrations inferred from the analytical model were compared with the nominal values to show good agreement over the concentration range of 189−805 ppm with a standard deviation <3%. When the QCL wavelength was locked at the line-center of the molecular transition, it was of interest to find that the theoretical model was simplified to that used for near-infrared HPSDS with an electro-optical modulator for laser modulation.

Research Area(s)

  • Frequency modulation, Heterodyne detection, Laser dispersion spectroscopy, Quantum cascade laser

Citation Format(s)

Theoretical and Experimental Study of Heterodyne Phase-Sensitive Dispersion Spectroscopy with an Injection-Current-Modulated Quantum Cascade Laser. / Wang, Zhen; Cheong, Kin-Pang; Li, Mingsheng; Wang, Qiang; Ren, Wei.

In: Sensors (Switzerland), Vol. 20, No. 21, 6176, 11.2020.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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