Integrated optical phased arrays for lidar applications

Abstract

It is no wonder that research in Si photonics (optical components embedded on a silicon platform) has bloomed so rapidly the last few years. Combining low loss, strong refractive index contrast (and, thus, light confinement), with electro-optical and thermo-optical effects, allows for the fabrication of dense and complex electro-optical Si photonics systems. Moreover, because it is based on the well-established platforms of the CMOS industry, Si photonics is expected to rapidly shift from a research field to the production of high volume, low cost, complex, integrated electro-optical systems. One class of systems receiving increasing interest are Nanophotonic Phased Arrays (NPAs), which offer free space emission of a manipulated beam that can be steered, focused, have controlled angular momentum and even create holograms. Still, some substantial challenges remain in applying these NPAs to real systems. Large cell size and spacing between adjacent antennas produce multiple beams and reduce effective steering angle. In addition, small beam angle requirements and large aperture in NPAs receivers demand large phased array size. In order to allow for both steering angle and large aperture, a large array with small cell size is required resulting large number of unit cells in one array. In this work, we first propose two metallic nanoantennas to couple between a waveguide mode to free space radiation. Then, by combining existing Si photonic components like directional couplers and modulators with optical antennas and phase shifters that were designed for this goal we demonstrate, in this work, several NPAs for various applications. Using unique architecture, we then, specifically focus on a, NPA based, lidar. These lidar systems are essential components in any autonomous system maneuvering in an undefined environment. An on chip lidar like this one can serve, for example, in the automotive industry for safety enhancement and to allow autonomous driving functionality at an affordable price.