Date of Award
Master of Science (MS)
Photonic integrated circuits (PICs) have significant value in today’s world of research. They enable devices to experience large reductions in size, weight, operation power, and cost (SWAPc), making photonic technology more accessible than ever. The functionality of PICs is greatly enhanced due to the realization of both active and passive devices within a single device structure. This is made possible through hybrid integration, which utilizes various coupling methods to transfer light from an active chip to a passive chip. Hybrid integration technology tremendously expands the capabilities of PICs, leading to a plethora of applications. One significant application is that of narrow linewidth lasers. Narrow linewidth lasers are necessary for many emerging applications including laser spectroscopy, light detection and ranging (LiDAR), optical communication, and other forms of optical measurement. Narrow linewidth lasers have a low phase noise, making them ideal for measurement applications. Achieving narrow linewidth within a semiconductor laser package is of increasing importance due to its smaller form factor, allowing such devices to be employed in a plethora of fields that require a small device footprint. External cavity lasers are usually employed to achieve these characteristics by using hybrid integration to couple light from an active source into a passive waveguide, the external cavity, which greatly extends the incident photon lifetime, thus decreasing linewidth. This passive device structure is highly dependent on micro-ring resonators to couple light to and from the waveguide, making the coupling coefficient an integral parameter to the success of external cavity lasers. The passive device structure in this work utilizes the thermo-optic effect of a passive waveguide within a Mach-Zehnder Interferometer integrated with a racetrack resonator to control how much light couples into a feedback waveguide, thus tuning the linewidth using a thermo-optic heater. This in turn shows the tuning of the ring resonator coupling coefficient. Devices of similar structure have previously been used to create widely tunable lasers and optical switches, but to our knowledge, have not been used to tune laser linewidth in such an application.
Porter, Charles, "Tunable Linewidth Chip-Level Lasers Using Hybrid Integration Methods" (2023). All Theses. 4095.