Efficient optical input/output interfaces between photonic chips and fibers or free-space ports are indispensable building blocks for a wide range of applications. Here, we present our progress in the development of silicon nitride grating couplers and compact silicon antennas.

This paper presents our advancements in silicon integrated photonics for telecommunication and data communication. Our key innovations, including integrated subwavelength gratings, demonstrate promising improvements in device performance and fabrication tolerance.

We report on an optimized polarization-insensitive grating design based on subwavelength metamaterials and L-shaped structures in a 500 nm silicon on insulator platform. The grating achieves the same scattering angle of 10° with similar efficiency for TE and TM modes based on 3D FDTD simulations.

Coupling of light between integrated photonic chips and optical fibers or free-space ports requires high efficiency optical elements to accommodate demands for wide range of applications. Here, we present recent advances in the development of low-loss silicon nitride grating couplers and compact silicon-on-insulator nano-antennas with high-directionality.

Surface gratings are key devices on photonic chips to enable a free-space light coupling or chip interfacing with optical fibers. These elements can be employed in a variety of applications, ranging from optical interconnects and sensing, to light detection and ranging (LIDARs) and free-space communications. For LIDARs and free-space communications, dualpolarization gratings are important in modern optical phased arrays. However, surface gratings in silicon photonics are intrinsically polarization-sensitive due to the strong geometrical birefringence of the waveguides. In this work, we present a design of polarization-insensitive photonic nano-antennas in the silicon-on-insulator (SOI) platform. The proposed antennas have a L-shaped radiating profile with sub-wavelength metamaterials to simultaneously provide polarization independence and high radiation efficiency. The optical antennas are designed on a 300 nm thick SOI with a 3 μm thick buried oxide layer. The antenna has a compact footprint of 6.5 μm x 3.18 μm and critical dimensions larger than 50 nm, which are feasible for public silicon-foundry processing and fabrication. At the nominal wavelength of 1.55 μm, the antennas have a radiation efficiency of 50% and 21% for the TE and TM polarized light, with emission angles of -17° and -21°, respectively. Polarization-independent nano-antennas in mature SOI platform offer great potential for multi-element photonic circuits required by LIDARs and free-space communications.

Optical phased arrays in silicon photonics are an emerging technology for free-space communications and light detection and ranging (LIDAR). While traditional LIDARs with discrete components and mechanical beam steering are difficult to integrate and scale, silicon-based arrays have taken a massive leap forward in developing beam steering systems with compact footprint and high performance on a single chip. Here, we report our results in the development of chip-scale circular phased arrays. Arrays formed in a grid of concentric rings are shown to suppress the sidelobes, expand the steering range and obtain narrower beamwidths, with large spacing between optical elements.

Optical Phased Array (OPA) has emerged as one of the most popular technologies in recent years. The integration of optoelectronics components on-chip allows the OPA to steer the beam to achieve ranging, detection, and free-space communication without having any moving parts. The thesis includes two parts. Firstly, a polarization-independent optical surface grating antenna designed for OPA is presented. The designed antenna emits both quasi-transverse electric (TE) and quasi-transverse magnetic (TM) modes towards the same angle with similar beamwidth. With the increasing demanding for mode-division multiplexing systems, the incorporation of such antenna in an OPA system allows an additional channel of data transmission while preserving the steerability of the array. In the second part of the thesis, the optical testing setup for a fabricated on-chip OPA system is designed and presented. With the testing setup designed and assembled, a comparison between the observed and simulated far-field images is also presented.

The demand for optical technologies in space is growing rapidly driven by the advent of low-earth orbit satellite “mega-constellations” providing global communication services. Free space optical communications between satellites in low earth orbit presents a number of technology challenges related to maintaining stable links between two satellites separated by thousands of kilometers. One principal challenge is the development of mechanically robust, mass-producible beam-steering technologies with low SWaP, and recurring cost. One potential solution to this challenge is to replace costly mechanical steering mechanisms with beam-steering elements such as on-chip optical phase arrays. This work presents ongoing research towards the development of an on-chip wide-steering optical phase array for inter-satellite communications. The presentation will cover the system architecture, component design, and control algorithms for synchronizing many emitters into a single output beam.