Phase-locked taper array for mid-infrared quantum cascade lasers with Talbot cavities

Power scaling in large-area quantum cascade lasers (QCLs) often leads to a degradation of beam quality and the emission of multi-lobed far-field patterns. In this study, we present a tapered QCL array featuring an integrated Talbot cavity on one side of the array, employing a diffraction coupling scheme. By controlling the Talbot length to one-half the Talbot distance (Zt/2), phase mode operation can be selectively achieved. Optimized in-phase mode operation is attained through careful adjustment of the Talbot cavity length. The far-field radiation pattern for in-phase operation comprises five lobes, with a central maximum lobe exhibiting a half-maximum width of 4.8°, accompanied by four side lobes. The separation between adjacent lobes measures approximately 14.3°. Ongoing research efforts are crucial to achieving enhanced beam performance and minimizing optical losses associated with integrated Talbot cavities.