A wideband 1×4 optical beam-forming chip based on switchable optical delay lines for Ka-band phased array

Abstract Comparing with electronic beam forming, integrated optical beam forming is very promising for optical controlled phase array system, because much broader band beam steering can be achieved without the beam squint effect. The single channel optical true time delay lines based on the cascade mircoring resonators and switched optical delay waveguides have been extensively investigated. The optical beam forming chip based on multi-channel microring resonators have also been demonstrated, however only limited working bandwidth were obtained due to their inherent tradeoff between the delay and bandwidth. The bandwidth limitation can be overcome by using integrated optical beam forming chip composed of switched optical delay waveguides, which has not been demonstrated and evaluated. Here, a 1 × 4 optical beamforming chip with four integrated switchable delay lines units designed to control the Ka-band phased antenna arrays is proposed and demonstrated experimentally. The maximum delay of 96 ps with a delay increment about 3.02 ps/stage was obtained, which is in accordance with the design well. Based on the measured delay times, the directional diagrams of the optical beamforming network were simulated and beam angle coverage of 90° can be achieved. Furthermore, a magnitude response experiment was carried out to evaluate the performance of the optical beam forming chip, and a remarkable working bandwidth of 29 GHz was achieved.