Fabrication of high-Q suspended AlGaAs microresonators for efficient Kerr comb generation

AlGaAs is a promising integrated nonlinear photonics material with enormous optical nonlinearity and high refractive index. Nevertheless, presently AlGaAs microring resonators exhibiting high-quality factors and tight optical confinement rely predominantly on wafer bonding techniques, which entail an intricate fabrication process. Here, we present suspended AlGaAs waveguides and resonators as a viable platform for high efficiency integrated nonlinear photonics. The suspended microring resonator formed by combined plasma dry etching and chemical wet etching exhibits an intrinsic quality factor Q of 2.1×106, corresponding to an optical loss of 0.28 dB/cm, and Kerr comb generation with milliwatt level threshold is recorded. The proposed scheme can be implemented with a relatively simple fabrication process, as it eliminates the need for wafer bonding. Without the hinderance of SiO2 or Al2O3 claddings, the air-clad suspended AlGaAs platform lends itself directly to applications in the mid-infrared region. Our demonstration opens up a prospect for employing AlGaAs devices in integrated nonlinear photonics.