Energy-efficient Integrated Optical Phased Array on Silicon-on-Insulator Platform

As a non-mechanical beam steering technique, optical phased array (OPA) is becoming a promising method for solid-state light detection and ranging (LiDAR) and
free-space optical communication. Significant progress has been achieved for the integrated OPA, such as large scalability, low power consumption, and large beam steering range. Moreover, silicon photonics is becoming a mature technique for large-scale photonic integrated circuits (PICs) owing to its compatibility with Complementary Metal Oxide Semiconductor (CMOS) process. Now, silicon photonics has been widely regarded as a suitable platform for large-scale OPA integration. In this thesis, we successfully demonstrated two kinds (racetrack-spiral and roundspiral) of energy-efficient silicon integrated optical phase shifter based on the thermooptic effect. Besides the low power consumption of the proposed phase shifters, they also exhibit a well-balanced overall performance on low insertion loss, high modulation bandwidth, and a small footprint. The best experimental result that we have already achieved on a round-spiral phase shifter for the insertion loss, power consumption, modulation bandwidth, and footprint are 0.6 dB, 3.1 mW/π, 34 kHz, and 42 µm × 42 µm, respectively. The proposed round-spiral phase shifter can benefit the large-scale silicon photonics integrated circuits as an efficient fundamental unit and is already been used in large-scale OPAs. By utilizing the well-balanced performance phase shifter, we fabricated two energyefficient 120-channel 1D-OPAs. The first demonstrated 1D-OPA utilizes Gaussian power distribution in both horizontal (φ) and vertical (θ) directions to achieve high sidelobe suppression ratios (15.1 dB and 25.8 dB, respectively). The steering angle range is 25° × 13.2°, and the beamwidth is 0.31° × 0.07° with an aperture size of 0.363 mm × 2 mm. The measured total power consumption and efficiency are 332 mW and 2.7 mW/π. The second demonstrated 1D-OPA has ultra-sparse nonuniform pitches to achieve high resolution of 0.13° and large steering angle range of 162° × 13.7°. The maximum side lobe suppression ratio (SLSR) is measured to be 6 dB. The measured total power consumption and efficiency are 469 mW and 3.5 mW/π. An attempt on large-scale 2D-OPA has been made. we fabricate a 32 × 32 2D-OPA with a uniform pitch of 28 µm. Next step, the 2D-OPA will be characterized.