Silicon photonics leverages advanced microelectronics fabrication platforms to realize ultra-miniaturized, complex, low cost, size, weight and power optical systems on chip that can be monolithically integrated alongside state-of-the-art electronic circuits. The applications for silicon photonics require ever more stringent performance specifications, needing lower loss, higher performance devices. However, the design of high performance devices is often impeded due to the sensitive nature of light-matter interaction and the tendency of light to scatter and radiate.
In this dissertation, I present the design of high performance radiative and resonant silicon photonic devices by efficiently controlling light propagation and radiation. Two types of radiative photonic devices are presented. The first are grating couplers for low-loss fiber-to-chip coupling. These grating couplers are designed to be readily implementable in wafer-scale CMOS and CMOS-photonics platforms by using a dual-layer structure to break vertical symmetry. A unique bandstructure synthesis method is presented for designing the grating couplers from first principles. A variety of grating couplers are designed for both the 45RFSOI CMOS platform and the 45CLO CMOS-photonics platform, with measured insertion losses comparable to the state-of-the-art. Along with low-loss grating coupler designs, I also conceive and demonstrate a new type of polarization-insensitive 1D grating coupler (PIGC) using a "corelet" metamaterial waveguide that removes effective index birefringence.
I demonstrate a PIGC in the 45CLO platform with a measured 1 dB polarization-dependent-loss bandwidth of 73 nm. The second type of radiative photonic devices are a new type of large-area, dispersive optical phased array named the serpentine optical phased array (SOPA). The SOPA combines a serpentine delay line with rows of grating couplers to realize a wavelength-controlled beam steering aperture. The design was conceived to maximize the radiating aperture while having minimal operating complexity. The theory and design of SOPA devices are presented, and a variety of SOPA devices are fabricated and characterized. Two applications for the SOPAs are investigated. The first is lidar and imaging, with initial demonstrations of ranging, Vernier'ed bi-static arrays for grating lobe link suppression, and F-BASIS imaging. The second is using SOPAs for spectroscopy. By combining the SOPA with a detector array, I am able to realize a compact and high-resolution spectrometer. An initial prototype has a spectral resolution of approximately 16 pm and working bandwidth from 1540 to 1650 nm, resulting in a resolving power of approximately 100k which is comparable to crossed-dispersion spectrometers but over 100 times smaller in volume. Finally, I present the design and characterization of high Q and compact racetrack resonators using a thick-SOI platform. Using the racetrack resonators, I demonstrate a four-channel, 100 MHz passband filter bank for RF-photonic signal processing.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/45485 |
| Date | 17 January 2023 |
| Creators | Zhang, Bohan |
| Contributors | Popovic, Milos A. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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