Mode-hop compensation for intracavity sensing via chip voltage in an external-cavity QCL

In this paper, we describe a technique to perform intracavity gas sensing by detecting changes in the QCL voltage. The influence of mode-hops is compensated by a data acquisition and processing based on a dual wavelength scanning. This allows to perform gas detection over the full cavity spectral range ( 1277 cm^-1-1348 cm^-1 ) without the use of a mode-hop free setup. First results of measurement of the CH_4 absorption spectrum are presented.