Self-aligned coupled cavity GaAs/AlGaAs midinfrared quantum-cascade laser

A monolithic GaAs/AlGaAs quantum-cascade laser with self-aligned focused ion beam-cut coupled cavities, emitting in the range of lambda=9.4 mu m is demonstrated. Separate pulsing of two optically coupled laser sections enables control of the lasing in single-mode and in multimode regimes. Side mode suppression ratios better than 25 dB are shown. Mode control over two single modes spaced by 3.6 cm(-1) is presented. An optical output intensity modulation in a range of 20 dB is achieved. The laser exhibits a peak output power in the range of 180 mW at cryogenic temperatures. The observed mode spacing is in a good agreement with the calculation. (C) 2000 American Institute of Physics. [S0003-6951(00)02734-0].