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Silicon photonic MEMS building blocks for low-power programmable circuits

Time: Fri 2022-11-25 09.00

Location: F3, Lindstedtsvägen 26 & 28, Stockholm

Video link: Zoom link for online defense

Language: English

Subject area: Electrical Engineering

Doctoral student: Pierre Edinger , Mikro- och nanosystemteknik

Opponent: Assistant Professor Sangyoon Han, Daegu Gyeongbuk Institute of Science and Technology

Supervisor: Kristinn Gylfason, Mikro- och nanosystemteknik; Frank Niklaus, Mikro- och nanosystemteknik

QC 20221104


Silicon photonics, or the confinement and control of light in integrated silicon waveguides, has rapidly grown from research labs to high-end chips for telecommunications. With the associated improvements in waveguide performance, the technology is promising for a wide range of new applications, from computing to sensing. However, current chip implementations of such applications are limited in scale. The available actuators used to control the circuits do not have the performance needed as building blocks for large circuits requiring thousands of actuators.

Today’s silicon photonic circuits rely mainly on heaters and the thermo-optic effect for actuation. It enables the monolithic integration of reconfigurable building blocks in silicon photonic foundries with low optical losses and relatively short optical lengths. However, such heater-based building blocks consume over 1mW per device. Opto-electronic actuators are also available in silicon photonic foundries for high-speed modulation but are lossy and long.

Micromechanical actuators for silicon photonics could provide the missing technology for scaling photonic circuits. Silicon is a material with excellent mechanical properties, and MEMS actuators can therefore be designed on the same layers used for waveguides. Electrostatic MEMS actuators consume very low power (<1nW static leakage per device), can achieve optical losses on par with state-of-the-art thermo-optic devices, within shorter optical lengths, and have response times in the μs range. However, such actuators require the partial suspension of silicon structures for movement, which is not currently available in silicon photonic foundries and presents additional challenges for commercial packaging.

This thesis aims to bring large-scale photonic circuits closer to reality by integrating low-power and scalable silicon photonic MEMSactuators in a silicon photonics foundry platform. MEMS-based building blocks with scalable optical performance were developed and included in photonic circuits. The devices and circuits were implemented on a silicon photonics foundry platform (IMEC’s iSiPP50G)with a few foundry-compatible post-processing steps. Finally, a solution for wafer-level sealing of the MEMS actuators was developed, compatible with subsequent packaging and enhancing the mechanical performance of the devices.