A Co-Integrated Optical Phased Array, Mach-Zehnder Modulator and Mm-Wave Driver for Free-Space Communication

Fully integrated silicon-based optical phased arrays (OPAs) are promising devices due to their extremely narrow beam, compact size, and low power consumption. Their potential applications include light detection and ranging (LiDAR), three-dimensional (3D) imaging, holography and wireless optical communication (WOC) [1]–[6]. These applications require OPAs to have small size and efficient interfacing between the electronic and photonic integrated circuits (ICs). There have been substantial efforts to realize compact OPAs with CMOS ICs for LiDAR applications [2–3, 5]. [2] demonstrated a monolithic integration with 1024-element antennas and DACs into one single chip, and [3] employed 3D-integration to connect phase shifters in the OPA with DACs. For the interface between the phase shifters and their driving DACs, relatively low bandwidth (BW) signals below 200 MHz are sufficient [1]. In contrast, OPAs for WOC require broadband electrical driving signal up-to 30 Gbps from an RF-amplifier to a traveling-wave-electrode Mach-Zehnder modulator (TWE-MZM) [4]. For such broadband high frequencies, the electronic-to-photonic IC interface becomes highly vulnerable to parasitics, losses, and impedance mismatches. As a result, OPAs for high-speed WOC applications have only been presented using commercial MZMs and RF-amplifiers, which consume large area and power, as shown in Fig. 1 [4]–[6].