Silicon nitride integrated optical phased array devices, applications and systems.

Abstract

LiDAR (Light Detection and Ranging) relies on capturing 3D high-definition images of the surrounding environment using optical laser technology. Current technology focuses on expensive modules based on mechanical beam scanners which are susceptible to mechanical failure and high detection inaccuracies. The focus of this thesis is on silicon nitride integrated LiDAR systems and devices based on optical phased array (OPA) solid-state beam steering technology, which holds great potential for reducing the cost of LiDAR modules. The results of this work aim to address several key challenges of OPA technology such as power budget, scalability, fabrication limitations, broadband operation, and polarization-independent response. This work elaborates on the development of a 1D OPA system architecture based on Pockels effect optical phase shifters and 2D dispersive OPA transceiver and receiver systems. Specifically, it demonstrates the building blocks for such systems and it reports on a demonstration of a hybrid silicon nitride-lithium niobate OPA array with an aperture size of 1.5x0.3 mm², achieving a beam width of 0.2721^◦x0.196^◦ and a steering rate of 0.025 ± 0.0133^◦/nm. Nitrogen-rich SiN films are then patterned to create an etch-less OPA by means of a UV light emitting diode (LED), achieving a beam width of 0.4319^◦x0.1277^◦ and wavelength sensitivity of 0.025^◦/nm. To address challenges attributed to the bandwidth of grating coupler technology, the use of facet metallic mirror-based OPA is explored, yielding a simulated beam width of 1.161^◦ in θ-direction for a 32-element 1D array spaced at 2 μm, while showing no beam steering when swept from λ = 1.52 - 1.63 μm. It then explores the use of integrated-mirror 1D and 2D OPA frameworks to reduce in half the number of active elements and the footprint required for free-space optical switching applications. Using the same concept, we have designed, fabricated, and characterised a double-port 1D OPA that has a large angular field of view of 20.9^◦. Finally, the integration of low-loss non-volatile phase change materials Sb₂S₃ (<0.04 dB μm⁻¹) and Sb₂Se₃ (<0.09 dB μm⁻¹) in the SiN platform are explored as means of enabling tunable photonic devices such as Mach-Zehnder interferometers and bi-directional Ring Resonators, to alleviate the power requirements of a LiDAR system.

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Identifiers

ORCID for Frederic Gardes: orcid.org/0000-0003-1400-3272

ORCID for Harold Chong: orcid.org/0000-0002-7110-5761

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