UC Irvine

The Free space optical (FSO) communication has long been considered a promising solution for high-speed broadband data transfer. A conventional FSO receiver consisting of a focusing lens and a small high-speed detector works efficiently for a limited range of angles of arrival (AoA). This makes the optical link vulnerable to AoA fluctuations jitter. Even with a dedicated Pointing, Acquisition, and Tracking (PAT) system, residual jitter with variance in the range of microradian is unavoidable in FSO communication. The jitter causes BER fluctuations over a long time. Moreover, multi-beam optical communication in which one receiver needs to connect with multiple transmitters dispersed in 3D space at the same time cannot be implemented with the conventional receiver. This thesis presents two receiver designs based on metalenses that can offer solutions for these problems. To reduce the AoA fluctuation, a metalens is introduced at the focal plane of the bulk aperture lens of a conventional receiver. The phase profile of the lens is optimized to allow efficient capture of beams with AoAs as large as 2.5mrad. This is a significant improvement over a conventional receiver without metalens, which can capture only 195μrad with the same efficiency. For multi-beam communication, a two-metalens receiver system with optimized phase profiles is proposed. A proof-of-concept three-beam communication link is demonstrated in which the maximum AoA of 2° can be captured with 67% efficiency. This shows 35X improvement over conventional systems with a single detector in terms of acceptable AoA. The performances of the proposed receivers are analyzed with diffractive optics calculation. Metalens unit cells at two different wavelengths (1μm and 1.55 μm) are presented in this thesis. Full metalens systems are created based on the phase response of unit cells with varying diameters and simulated in Lumerical and COSMSOL. The simulation result validates the efficiency of the proposed receivers. When implemented, the proposed receiver will increase the capacity of communication links as well as maintain the same capacity over a long period of time. The proposed method can further be used to design receiver modules for specific situations such as for CubeSat/ astrophysical observation.