Electromechanical phase shifters and power splitters for re-configurable integrated photonics

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Photonic integrated circuits (PICs) are part of many growing applications, from LIDAR to biosensors. The complexity and functionality of these systems are only expected to become more demanding, so programmable PICs are expected to simplify the development effort by providing the same re-configurable circuit functionality as field programmable gate arrays (FPGAs) did for electronics development. The key devices for the development of programmable PICS are phase shifters and power splitters that allow for the arbitrary complex weighting and routing of optical signals on a chip. Each operation to change the state of the circuit using a phase shifter or power splitter consumes energy, so technologies that scale well in terms of power consumption are critical to achieve the necessary integration density. Unfortunately, common thermo-optic devices available in most PIC process kits will always require constant power to change and maintain the circuits configurations. A different technology that changes the paradigm is needed. Micro-electromechanical system (MEMS) based devices have emerged as such a displacing technology because they can be designed to have zero static power consumption when holding the circuit state. This dissertation provides key insights into the development of MEMS phase shifters and power splitters. Specifically, techniques for low insertion loss and process integration with silicon nitride photonics are presented. Coupled mode theory is applied to the design of the MEMS phase shifter to define a loss-loss geometry based on the orthogonality of modes. The concept is then expanded to define optimization objectives based that only require mode solver simulations. In simulation, the optimized silicon nitride designs proposed could achieve as little as 0.022dB insertion loss for a 100um long device. To experimentally demonstrate the low-loss designs, a novel silicon nitride process was developed. High aspect ratio structures needed in the design are achieved via a trench filling process. The release of the MEMS is based on XeF2 etching of silicon and not the silicon dioxide substrate or cladding of the silicon nitride photonics. The fabricated 100 um long MEMS phase shifters achieved 0.48dB zero voltage insertion loss with less than 0.05dB phase dependent loss over a pi phase range. Using the same process stack, an initial demonstration of a novel tunable power splitter based on a MEMS tunable directional coupler is made.


Type of resource text
Form electronic resource; remote; computer; online resource
Extent 1 online resource.
Place California
Place [Stanford, California]
Publisher [Stanford University]
Copyright date 2022; ©2022
Publication date 2022; 2022
Issuance monographic
Language English


Author Abebe, Nathnael Solomon
Degree supervisor Solgaard, Olav
Thesis advisor Solgaard, Olav
Thesis advisor Miller, D. A. B
Thesis advisor Vuckovic, Jelena
Degree committee member Miller, D. A. B
Degree committee member Vuckovic, Jelena
Associated with Stanford University, Department of Electrical Engineering


Genre Theses
Genre Text

Bibliographic information

Statement of responsibility Nathnael Solomon Abebe.
Note Submitted to the Department of Electrical Engineering.
Thesis Thesis Ph.D. Stanford University 2022.
Location https://purl.stanford.edu/gt624vr5764

Access conditions

© 2022 by Nathnael Solomon Abebe
This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).

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