Beam steering and lateral hole burning in mid-infrared quantum-cascade lasers

We investigated the beam-steering phenomenon of quantum-cascade lasers emitting at ~7.8 µm wavelength, operated in pulsed mode at heat sink temperatures around room-temperature. The lasers have a dimension of 12 µm × 1500 µm. The observed beam-steering phenomenon has been explained by considering spatial hole burning in the population inversion of conduction electrons along the lateral direction. Rate equations have been set up to describe the lateral hole burning effect. The simultaneous oscillation of at least two lateral modes, which are a consequence of the lateral hole burning and at the same time possible cause of beam steering, has been verified by high-resolution spectroscopy.