Red, green, and blue edge-emitting devices for beam scanning light engine architectures: from single emitters to arrays

Laser beam scanners are of strong interest, as they offer a compact and low-power consumption solution for head-worn AR-displays and, more in general, for efficient and focus-free projection displays. In this framework, EXALOS has been leading the research and development of active light sources, focusing on optimizing red, green, and blue edge-emitting devices, including superluminescent diodes (SLEDs) and laser diodes (LDs). This work provides an overview of the performance achieved by single-emitter SLEDs and low-threshold LDs based on GaN, as well as AlGaInP, III-V semiconductors. Furthermore, we report on the development of emitter arrays. In particular, narrow-pitch devices with an emitter-to-emitter spacing of 10 μm and also a novel device design featuring both anodes and cathodes on the top chip surface are reported. The individual cathodes are fully independent and electrically insulated, ensuring an emitter-to-emitter resistance close to 1MOhm. Compared to conventional arrays with common cathode, the new architecture allows for integration with industry-standard current-sink drivers for efficient multi-LD modulation.