InP-based grating antennas for high resolution optical beam steering

Optical beam steerers on InP integrated photonics have not been able to offer high angular resolution, due to the technological challenges in realizing a large emission aperture. In this paper, we propose the creation of waveguide-based grating antennas fabricated in SiO2 super-cladding on InP membrane on silicon (IMOS) to achieve simultaneously high resolution and good compatibility with InP-based active devices. By exploiting the high dry etch selectivity between SiO2 and InP, a tolerant fabrication process is proposed and demonstrated, allowing for high controllability in the process. Device parameters including buffer thickness and pitch have been explored to obtain an optimized design. A 2-mm long grating antenna is fabricated and shows a record narrow full-width-half-maximum angular beam width of 0.05° and a high spatial resolution of more than 250 points when the wavelength is tuned over a range of 100 nm.