Regrowth free monolithic integration platform on GaAs using vertical twin waveguides

Photonic integrated circuits (PICs) have revolutionized optical systems by integrating multiple components onto a single chip, reducing system cost, size, weight, and power. The PIC market is currently dominated by indium phosphide (InP) and silicon photonics (SiPh) platforms for optical communication in the 1.3 μm and 1.55 μm spectral bands. More recently, PICs have been explored for other applications including sensing, lidar, free-space optical communication, and quantum metrology, many of which require wavelengths that are inaccessible with traditional InP and SiPh PICs. The gallium arsenide (GaAs) material system in particular offers distinct advantages for applications requiring high optical output power or operation in the 0.65-1.3 μm wavelength range. In this work, we present simulation results for a regrowth-free approach to monolithic active-passive integration on GaAs using tapered couplers in a vertical twin waveguide architecture. Selectively oxidized aluminum gallium arsenide layers with high aluminum fraction are used to provide lateral optical and carrier confinement in the active region and to facilitate efficient active-passive coupling in the taper. This approach demonstrates a simulated coupling efficiency of more than 98% with significantly relaxed requirements for lithographic resolution compared to tapers without lateral oxide confinement. Active region simulations further validate the design with simulated Fabry-Perot lasers characterized by high slope efficiency (∼1 W/A) at a lasing wavelength of 975 nm. This regrowth-free solution paves the way for compact and efficient monolithic GaAs PICs with potential for applications such as satellite-based lidar and free-space optical communications.