On‐Chip Metamaterial Antenna Array with Distributed Bragg Deflector for Generation of Collimated Steerable Beams

Abstract The generation of collimated steerable beams of light is a fundamental function in optics needed in many applications, including free‐space optical communications, remote sensing, and light detection and ranging. Implementing large‐aperture light emitters directly on a photonic integrated chip without using external optics and expensive alignment systems is an outstanding challenge in integrated photonics. Here, the experimental demonstration of a new integrated antenna array architecture that uses a compact feeding circuit is reported. The design is based on an apodized Bragg deflector working as a low‐loss (<0.3 dB) ultra‐compact beam expander, which generates a 40‐µm‐wide on‐chip Gaussian beam that illuminates a one‐dimensional array of 112 optical antennas with a length of 1.5 mm. Each antenna comprises a metamaterial subwavelength grating waveguide core that is laterally loaded with an array of periodic radiative silicon segments. The device is fabricated on a 220‐nm silicon‐on‐insulator platform using a single etch process with a minimum feature size of 80 nm. An antenna array with a power gain of 50 dB, a radiation efficiency of −3.8 dB, and a far‐field angular divergence of 1.8° × 0.2°, in a wavelength range of 1500–1580 nm is presented.