Coherent beam combining of optical phased array chips enabled by low-frequency half-wave voltage measurement

To enhance the far-field beam quality of the optical phased array (OPA) chip, this paper proposes what we believe is a novel OPA coherent combining architecture based on inter-chip interference. In this architecture, phase modulators are employed for inter-chip phase control, with their half-wave voltages serving as critical parameters for achieving high-precision phasing. To address the low-frequency (DC-kHz) phasing requirements in OPA coherent combining, a half-wave-voltage measurement method is proposed, based on which closed-loop coherent combining of two OPA chips is realized. Experimental results demonstrate that the far-field beam can be stably combined into a single-main lobe, with the divergence angle reduced from 0.181° to 0.066°. This significantly enhances beam quality, validating the effectiveness of the proposed architecture and measurement method.