Small and scalable laser source for AR glasses by flip chip of bare laser diode in silicon nitride PIC technology

A laser engine for AR glasses is demonstrated based on a silicon-nitride PIC using a flip-chip assembly process. By etching recesses in the silicon nitride PIC and flip chipping of bare Red, Green and Blue laser diodes a passive alignment method is provided. Process optimizations are demonstrated to optimize the output to ~30mW for Red, with a coupling efficiency > 70%. This shows the scalability of the approach to manufacture a small device (footprint is 4x4x1.5mm) in high volume The small form factor chip combined the 3 wavelengths into one spot and the optical output is optimized in performance for use in AR systems: Circular mode (1:1) and low Numerical Aperture difference (<0.06) over all 3 wavelengths. The device is tested with a Laser Beam Scanning test bed resulting in crisp and clear images, due to the optimized beam spot. The thermal behaviour of the device is modeled and measured. Given the LBS modulation techniques for AR applications, only passive cooling is needed, that fits the form factor of AR glasses. With this laser engine an LBS system is proposed with a volume < 0.8 cc and a weight of < 0.5 gram.