The side-lobe level (SLL) in optical phased array (OPA) systems should be reduced to ensure their high performance. We investigate theoretically the performance of an OPA based on optically injection-locked (OIL) semiconductor lasers. The phase and amplitude of the OIL laser are modulated by controlling the injection-locking parameters to reduce the SLL as well as to achieve beam steering. We successfully achieved an SLL reduction of >16 dB when compared with the uniform amplitude profile based on the application of the Taylor window function profile to the injection-locked OPA elements. The reduced SLL and high power efficiency achieved in this study can expedite the use of OPA in real field applications, such as free-space communication, imaging, and light detection and ranging (LIDAR).

We propose an equivalent electrical circuit model to evaluate the direct modulation performance of optically injection-locked (OIL) semiconductor lasers. We modeled the equivalent circuit of the OIL laser based on alternating complex envelope representations, simulated it using the Simulation Program with Integrated Circuit Emphasis (SPICE), and analyzed the frequency response of the OIL laser. Although the frequency response of the OIL laser is better than that of a free-running laser, its 3-dB modulation performance is degraded by the relaxation oscillation that occurs during direct modulation of the semiconductor laser. To overcome this limitation and maintain the maximum modulation performance within the entire locking range, we also designed an electrical filter to preprocess the electrical modulation signal and compensate for the non-flat modulation output of the OIL laser. The damping ratio of the directly modulated OIL laser increased by 0.101 (280%) and its settling time decreased by >0.037 (44%) when the electrical compensation circuit was added, exhibiting a flat 3-dB modulation bandwidth of 28.79 GHz.