Light detection and ranging (LiDAR) is a remote sensing technology that can actively detect and obtain spatial distance, speed, and other information with high precision, realizing four-dimensional (4D) imaging of targets. It has broad application prospects in emerging fields such as intelligent driving and unmanned aerial vehicle (UAV) surveying and mapping. In the traditional mechanical LiDAR, the optical system is usually composed of multiple optical components arranged in a specific spatial order, such as laser arrays, lens systems, and detector arrays. The use of discrete components makes assembly difficult, costly, and less mechanically stable. The number and type of components, arrangement order, and component spacing all affect the optical system’s performance. It is not suitable for applications such as small unmanned systems and the precision motion and control of robotic arms. Therefore, there is an urgent need for LiDAR to develop in the direction of solid-state and miniaturization.

In this paper, we introduce the technical development requirements of LiDAR from traditional mechanical techniques to all-solid-state applications. It focuses on the all-solid-state and miniaturization characteristics of silicon-based optical phased array LiDAR chips, detailing the basic principles and typical implementation methods of one-dimensional and two-dimensional phased arrays. The state-of-art research on silicon-based optical phased array chips for a large field of view is elaborated. Silicon photonic integrated optical phased arrays are compatible with proven complementary metal-oxide-semiconductor (CMOS) manufacturing process, enabling large-scale integration. They offer advantages such as low cost, low power consumption, fast scanning speed, and arbitrary direction control. Relying on the rapid development of silicon-based photonics, these arrays have gradually become a hotspot in all-solid-state LiDAR research. Currently, there are two main schemes to achieve two-dimensional beam scanning in silicon-based optical phased array chips: the first scheme uses a one-dimensional phased array antenna array, with a phase shifter array to control scanning in one dimension, while the other dimension utilizes the diffraction characteristics of optical gratings to adjust the wavelength of the light source. The second scheme uses a two-dimensional phased array antenna array with two-dimensional phase tuning to achieve two-dimensional beam steering. For the first scheme, the beam scanning field of a one-dimensional optical phased array is related to the array element spacing; smaller array element spacing results in a larger field of view in the phase control dimension. In particular, aliasing-free scanning of a 180° full field of view can be achieved when the array period is less than half wavelength. Based on the principle of waveguide refractive index mismatch, a periodic bending modulated array is an effective method to reduce crosstalk between dense waveguides. Our research group implements a one-dimensional optical phased array chip based on the half-wave interval of a sinusoidal waveguide array, achieving a transverse beam scanning field of view of 120° with crosstalk between arrays less than -13 dB. In addition, the optical phased array based on sparse array technology breaks the periodicity in the waveguide array space, ensuring the position of the far-field high-order grating lobe no longer meets the interference phase length condition, thus expanding the beam scanning field of view. In the wavelength regulation dimension, the field of view is mainly limited by the tunable wavelength range of the light source and the antenna’s wavelength tuning efficiency. Ultra-high bandwidth tunable laser technology is challenging and costly, making it more feasible to improve wavelength tuning efficiency by optimizing the optical phased array antenna structure, a focus of researchers domestically and internationally. Reported schemes mainly include multi-wire and mode multiplexing. For the second scheme, a two-dimensional optical phased array with a rectangular antenna array can achieve grid-lobe compression to some extent. However, due to the large spacing of sparse array elements, there are still grid lobes at large angles, and the achievable field of view remains small. Our research group proposes an optical phased array chip with a sparse circular aperture architecture. The fabricated chip can realize full field of view scanning without grating lobes, effectively improving the optical phased array’s scanning field of view.

The two schemes for optical phased array chip technology each have their advantages and disadvantages. One-dimensional optical phased arrays depend on the performance of tunable laser light source, and their wavelength tuning efficiency needs further improvement. Although multi-dimensional multiplexing can improve wavelength tuning efficiency, a wavelength tuning bandwidth of 100 nm is needed to achieve large-angle beam scanning. Two-dimensional optical phased arrays eliminate the need for multi-wavelength tunable lasers, but the beam divergence angle and system loss are mutually restricted, primarily limited by the number and spacing of antenna array elements. Large-scale array integration and optical antenna optimization are necessary breakthroughs. As a remote sensing technology that can be used for active detection, LiDAR systems can obtain spatial distance, speed, and other information with high precision, enabling four-dimensional imaging of targets. It has broad application prospects in emerging fields such as intelligent driving and unmanned aerial vehicle surveying and mapping. In summary, achieving high-performance all-solid-state LiDAR with a large field of view, low loss, and low beam divergence angle still requires more in-depth research. With the rapid development of modern semiconductor processing technology, which is moving toward greater precision and large-scale integration, there is great potential for the commercial application of silicon-based optical phased array LiDAR chips in intelligent fields.