Light detection and ranging (LiDAR), combining traditional radar technology with modern laser technology, has much potential for applications in navigation, mapping, and so on. Benefiting from the superior performance, an all-solid-state beam steering realized by integrated optical phased array (OPA) is one of the key components in the LiDAR system. In this review, we first introduce the basic principle of OPA for beam steering. Then, we briefly review the detailed advances of different solutions such as micro-electromechanical system OPA, liquid crystal OPA, and metasurface OPA, where our main focus was on the recent progress of OPA in photonic integrated chips. Finally, we summarize the different solutions and discuss the challenges and perspectives of all-solid-state beam steering for LiDAR.

We propose and demonstrate a 1×2 power splitter enabling arbitrary power splitting ratios. The device is based on a directional coupler with subwavelength structure in the coupling region and a trapezoid-structure in one arm. The measurement shows that arbitrary power splitting ratios, equal to 50:50, 60:40, 70:30, 80:20 and 90:10, can be obtained over an >80 nm bandwidth with an excess loss about 0.65 dB at 1550 nm, while the footprint is only 11.5 μm ×1.315 μm. The proposed arbitrary ratio power splitter shows promising application prospect in photonic integrated circuits.

We propose the silicon photonic optical phased array (OPA) with large scanning angle by using polarization multiplexing. A Mach-Zehnder interferometer (MZI) switch together with a polarization splitter/rotator is utilized to select the polarization mode input to the OPA. By optimizing the OPA grating emitter, the steering angle can be doubled with the input of the TE/TM polarization modes. An 1 × 16 silicon-based optical phased array with polarization multiplexing is designed as an example. The simulation results show that 77.4° lateral beam steering with no sidelobes via phase tuning and 28.2° longitudinal beam steering via wavelength tuning can be realized.

We propose and demonstrate a silicon photonic optical phased array (OPA) with ultra‐low sidelobe level. The arbitrary ratio power splitters (ARPSs) are introduced to manipulate the amplitude distribution between different channels and suppress the sidelobe level. A 32‐channel OPA has been designed and demonstrated with the amplitude distribution determined by preferred Chebyshev method. The experimental results indicate that the sidelobe suppression ratio (SLSR) can be up to 25.3 dB. The measured field of view (FOV) is 84° × 13° with divergence of 2.8° × 1.7°. Furthermore, the frequency‐modulated continuous‐wave (FMCW) based ranging has been also demonstrated experimentally by utilizing the OPA as the transmitter.

A grating coupler structure on a X-cut lithium niobate on insulator (LNOI) platform is designed and demonstrated. The utilized inverse design method is based on gradient-based adjoint optimization method, which is time saving and with more optimization degrees of freedom. For TE polarization, the high coupling efficiency of −3.3 dB is experimentally obtained. The maximum coupling efficiency is still −3.9 dB with the broadband 3-dB bandwidth of 90 nm. The grating coupler of high performance is realized by only single step etching and without bottom metal reflection layer.

We propose a large scanning range silicon optical phased array (OPA), which is polarization multiplexed and bi-directional with only one waveguide grating antenna array. Mach-Zehnder interferometers (MZIs) and polarization splitter-rotator (PSR) are utilized to select the polarization states and propagation directions of the input light to the waveguide grating emitter array. By optimizing the parameters of the waveguide grating, the longitudinal far-field steering range is increased by four times compared to that of the conventional ones among the same wavelength range. The simulation results show that the 54.5° longitudinal scanning range could be realized with the tuning wavelength ranging from 1500 nm to 1600 nm. The high wavelength tuning efficiency is up to 0.545 °/nm. The beam steering range in the lateral direction is 77.8° via phase tuning.