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Real-time gas sensing based on optical feedback in a terahertz quantum-cascade laser
We report on real-time gas sensing with a terahertz quantum-cascade laser (QCL). The method is solely based on the modulation of the external cavity length, exploiting the intermediate optical feedback regime. While the QCL is operated in continuous-wave mode, optical feedback results in a change of the QCL frequency as well as its terminal voltage. The first effect is exploited to tune the lasing frequency across a molecular absorption line. The second effect is used for the detection of thedoi:10.1364/oe.25.030203 pmid:29221052 fatcat:s3fp53qc3bam7pryfwbib6jqka