The laser-as-detector approach exploiting mid-infrared emitting interband cascade lasers: A potential for spectroscopy and communication applications

Abstract

Interband cascade lasers are exceptionally versatile, high-tech semiconductor lasers. They represent the latest generation of semiconductor lasers that generate radiation in the mid-infrared wavelength domain and are therefore preferred as coherent light sources in spectroscopy and free-space-communication setups. In this thesis they are used to evaluate the so-called laser-as-detector approach. The laser-as-detector approach is a well-known but little used technique that allows dispensing external optical detection units. A semiconductor laser itself is used as a detector, even though it is operating as usual. The principle is based on the fact that external optical perturbation change the charge carrier density in the interband-cascade-laser and manifest themselves accordingly in changes of the terminal voltage. Using the laser-as-detector approach, two spectroscopic methane sensors are then set up and their detection limits are evaluated. The laser-as-detector approach is then used to build a free-space-communication communication device without any detector.