Spectroscopy system using waveguide and employing a laser medium as its own emissions detector

A spectrometer comprising:

• (a) a sample chamber having at least one vapor sample therein;
• (b) a quantum cascade laser (QCL) comprising:
• (i) a QCL crystal having a first and second emitting facet for providing an electromagnetic beam, and an active region adjacent each of said emitting facets;
• (ii) an optical cavity comprising at least one mirror being external to said QCL crystal, and for redirecting the electromagnetic beam into the active region of said QCL crystal to provide optical feedback;
• (iii) the sample chamber being positioned to allow the electromagnetic beam to pass through there through;
• (iv) an excitation energy source to provide the QCL crystal with a constant current;
• and
• (v) a controller coupled to said QCL to determine absorption by the at least one vapor sample in the sample chamber based upon at least one detection signal from said QCL crystal.

A method of operating a quantum cascade laser (QCL) comprising:

• (a) providing a QCL crystal having:
• (i) a first and second emitting facet, and an active region adjacent at least one emitting facet, the at least one emitting facet for providing an electromagnetic beam;
• (ii) and a QCL excitation source for providing the QCL crystal with a constant current;
• and
• (b) determining the absorption by the at least one vapor sample in the sample chamber based upon at least one detection signal from said QCL crystal.