Discretely tunable single-mode lasers on GaSb using two-dimensional photonic crystal intracavity mirrors.

We report on single-mode emitting coupled cavity ridge waveguide lasers on the GaSb material system in the 2 µm spectral range using two-dimensional (2D) photonic crystals (PhCs). Eight rows of 2D PhCs lateral to the ridge waveguides act as intermediate mirrors and are used to create two coupled cavities. This leads to preferential emission at one single longitudinal mode in the emission spectrum with side mode suppression ratios of 30-35 dB. Monolithic integration of high reflectivity 2D PhC back mirrors allows the realization of cavity lengths as short as 300 µm with threshold currents as low as 18.5 mA while reaching output powers well above 18 mW. Under variation of driving current the lasers exhibit both discrete and continuous tuning behavior over a wide current range very well explicable by simulation of the sub-threshold spectra, rendering the devices especially interesting for multi-gas sensing by absorption spectroscopy.