Theses Doctoral

Scaling high performance photonic platforms for emerging applications: from air-cladded resonators to graphene modulators

Lee, Brian Sahnghoon

Silicon photonics accelerated the advent of complex integrated photonic systems where multiple devices and elements of the circuits synchronize to perform advanced functions such as beam formation for range detection, quantum computation, spectroscopy, and high-speed communication links. The key ingredient for silicon's growing dominance in integrated photonics is scalability: the ability to monolithically integrate large number of devices.

There are emerging device designs and material platforms compatible with silicon photonics that offer performances superior to silicon alone, yet their lack of scalability often limits the demonstrations to device-level. Here we discuss two of such platforms, suspended air-cladded microresonators and graphene modulators. In this thesis, we demonstrate methods to scale these devices and enable more complex applications and higher performance than a single device can ever acheive.

We present an effective method to thermally tune optical properties of suspended and air-cladded devices. We utilize released MEMs-like wire structures and integrated heaters and demonstrate efficient thermo-optic tuning of suspended microdisk resonators without affecting optical performance of the device. We further scale this method to a system of two evanescently coupled resonators and demonstrate on-demand control of their coupling dynamics.

We present an approach to achieve large yield of high bandwidth graphene modulators to enable Tbits/s data transmission. Despite their high performance, graphene modulators have been demonstrated at single device-level primarily due to low yield, ultimately limiting their total data transmission capacity. We achieve large yield by minimizing performance variation of graphene modulators due to random inhomogeneous doping in graphene by optimizing device design and leveraging state-of-the-art electrochemical delamination graphene transfer. We present for the first time, to the best of our knowledge, a statistical analysis of graphene photonic devices.

Finally, we present a graphene modulator that is versatile for photonic links at cryogenic temperature. We demonstrate the operation of high bandwidth graphene modulator at 4.9 K, a feat that is fundamentally challenging other electro-optic materials. We describe its performance enhancement at cryogenic temperature compared to ambient environment unlike modulators based on other electro-optic materials whose performance degrades at cryogenic temperature.


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More About This Work

Academic Units
Electrical Engineering
Thesis Advisors
Lipson, Michal
Ph.D., Columbia University
Published Here
October 20, 2020