A review of photonic integrated optical phased array (OPA) for space optical communication is presented. We review and summarize the typical works of the photonic integrated OPAs with onedimensional and two-dimensional optical antenna array in recent years. The basic components of the photonic integrated OPA are introduced separately, including optical coupler, optical power division network, phase shifter, and optical antenna. In addition, the configuration of the optical antenna array and the control circuit are introduced for OPA beam steering. The basic principle and experiment setup for testing the radiation properties of the OPA are presented. A proof-of-concept nonuniform silicon integrated OPA with 64 antennas is designed and a one-dimensional beam steering range of 28° is achieved with beam width of about 0.25°. The challenges and development trends of large-scale integrated OPA chip applied in space optical communication are also discussed. INDEX TERMS Beam steering, large scale, optical phased array, photonic integration, space optical communication I. INTRODUCTION Recently, radio frequency (RF) communication has been widely used in our daily life, but the communication speed is low and cannot reach to a few Gbps. With the demand of large-capacity and high-speed communication, the communication frequency gradually expands to high frequency. Space optical communication possesses significant advantages of large communication capacity, convenient networking, concentrated energy and good security. With the rapid growth of satellite-to-ground and inter-satellite transmission bandwidth requirements, space optical communication will be an important means of highspeed inter-satellite communication and networking. The current satellite-borne laser communication terminal achieves acquisition, tracking and pointing (ATP) by using the mechanic servo and optical lens, but this method has some shortcomings, such as low steering speed, no beam agility, large volume and heavy weight. In the practical application of low earth orbit (LEO) satellite network with inter-satellite links, one of the satellite nodes of inter-satellite laser communication network needs to establish at least four links with its neighbors. As shown in Fig. 1, four links between LEO satellite A and its neighboring satellites B, C, D, and E are established, which include two links with satellite nodes in the same orbit and other two links with satellite nodes in different orbits. Due to the limitation of heavy weight and large volume of the mechanical servo and optical lens, the traditional beam-steering system cannot meet the requirement of inter-satellite networking for fast establishment of multiple links simultaneously.
