Lasers à cristaux photoniques pour spectroscopie infrarouge – CRISPI

The wavelength range spanning from 2 to 4 µm is of particular interest for spectroscopy. Many molecules of industrial interest exhibit in that spectral region intense absorption lines, and lasers and detectors to mesure them work cw at room temperature, thus enabling industrial applications. However, the emitting lasers must exhibit some specific features, such as a single frequency emission and some wavelength tuning capacities. This project aims to realise for the first time single frequency tunable laser diodes using photonic crystals and emitting in the mid-infrared, for spectroscopy applications in the 2 to 4 µm wavelength range. IES will grow by molecular beam epitaxy on GaSb the GaInAsSb/AlGaAsSb quantum well heterostructures constituting of the device. Based on the large expertise of IES on GaInAsSb/AlGaAsSb structures emitting around 2.3 µm, an important step will be the first quantum wells lasers working cw at room temperature beyond 3 µm. They will be studied and realised using type I active zone with GaInAsSb quantum wells and AlGaInAsSb quinary barriers. A full technological workflow on GaSb will be developed at LAAS-CNRS to realise a waveguide surrounded by photonic crystals. The full laser cavity is inspired from cleaved coupled cavities geometry (C3) and uses photonic crystals to optimize and stabilize the spectral filtering of these cavities. This technique should make lasers single mode and tunable over the whole gain spectral range, a highly regarded property for spectroscopy. These devices will be the first lasers using photonic crystals on GaSb. Fully characterized devices will be tested at LSP for cavity ring down spectroscopy (CRDS) experiments to measure sub ppm traces of methane, carbon monoxide and ammonia.