Quasi PT-symmetric design for single-mode high-power edge-emitting semiconductor lasers

Large-area lasers are utilized for generating higher optical powers. However, enlarged cross-sections for increased current injection lead to the introduction of high-order modes, decreased beam qualities, and limited applicability. Available mode filtering approaches such as adiabatic amplifiers, tapered designs, laterally inhomogeneous structures, and refractive index modulations mostly adversely affect the fundamental mode and require added steps and complexities in the fabrication. As a novel concept in quantum mechanics, PT-symmetric (PTS) designs have found their only experimental validation in optical devices. They have shown capabilities in high-order mode filtering by inducing selective modal losses on the coupled higher-order mode from a pumped main potential to a lossy partner potential. Again, these systems require precise adjustments to avoid affecting the fundamental mode. Here, we introduce the quasi-PTS concept, with reduced operational sensitivity, to selectively force loss on the high-order mode while keeping the fundamental mode intact. This design is based on adjusting the width of the passive partner to support the higher-order mode of the main potential as its first mode. We present experimental evidence for an electrically pumped, large-area edge-emitting laser with high-power emission above 400mW and high beam qualities below 1.2. Beyond prior proof-of-concept investigations, this study provides the first unambiguous demonstration of PTS applicability in designing laser geometries with industrial output power levels and emission characteristics.