Beam steering in quantum cascade lasers with optical feedback

Abstract

Quantum cascade lasers are semiconductor lasers based on intersubband transitions that have developed rapidly and become the most suitable mid-infrared laser sources, due to their compactness, efficiency and high room temperature performances. High-power mid-infrared quantum cascade lasers are performant sources for optical countermeasures, including night vision blinding and missile out steering. However, some drawbacks arise with high power lasers that usually lead to a strong degradation of the beam quality. For instance, beam steering is known to be one of the limiting factors inducing an irregular distribution of the optical power within the near-field beam profile. This phenomenon has already been observed in high power quantum cascade lasers before and can be explained by four-wave mixing interaction among the existing transverse modes. It dramatically degrades the far-field of the laser emission, and prevents its use for applications where high beam quality is required. In this work, we show for the first time that the use of a small amount of optical feedback reinjected into a high power quantum cascade laser emitting at 4.6 μm and with poor beam quality allows a total suppression of the beam steering effect without sacrificing the near-field profile.