End-fire optical phased array with a wide beam-steering for near-visible infrared applications

Recent emerging applications in LiDAR, free-space data link, projection, and imaging increase the demand for high performance optical phased array (OPA). The radiating elements considered for most applications are mainly diffractive elements such as gratings or photonic crystal waveguides. It has been shown recently that edge-emitting waveguide arrays, also known as end-fire, facilitate subwavelength spacing in IR range, which results in a large beam steering. For several applications such as data centers, sensing, and spectroscopy, the near-visible infrared OPAs are in high demand. We demonstrated an end-fire-based OPA at a wavelength of 852nm. The OPA is fabricated on a PECVD SiN-on-insulator platform offered by imec available through BioPIX300 technology. The waveguide is designed for the first fundamental mode with a cross-section of 550×300nm 2 . As shown in Fig. 1(a) , the optical input is divided into eight branches using a tree of optically optimized Y-splitters (insertion loss < 0.03dB). After each splitting level, four thermo-optical phase shifters are connected electrically in parallel. Phase shifting is enabled by a TiN heater on top of the waveguide with a length of L=90μm. The effect of thermal coupling length is considered after the first, second, and third splitter 4L, 2L, and L, respectively. This configuration provides a simple three-level resolution for beam steering resolution, all with the same applied voltage. To reduce the thermal crosstalk, adjacent channels are not active at the same time. Even- and odd channels are separated in an active mode, each responsible for left and right beam steering. The channels finally end at two microns before the chip’s edge with a center-to-center spacing of 800nm.

Recommended citation: K. Jamshidi et. al. (2021) "End-fire optical phased array with a wide beam-steering for near-visible infrared applications" Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) https://doi.org/10.1109/CLEO/Europe-EQEC52157.2021.9542770