Johannes Henriksson

EECS Department, University of California, Berkeley

Technical Report No. UCB/

December 1, 2025

Fueled by growing demand for cloud computing applications, such as machine learning, the scale, bandwidth, and power consumption of data center networks continue to increase, and with it, a demand for novel network technologies and architectures. One such emerging technology is the optical circuit switch, which can increase the performance, flexibility, and power consumption of data centers. The optical circuit switch presented here is an integrated, non-blocking, switch built on a scalable silicon photonics platform. The switching mechanism is based on vertically movable adiabatic coupler waveguides controlled by micro-electromechanical-system actuators, enabling sub-microsecond switching time. By using a crossbar architecture, where light traverses an ON-state switch unit cell only once, independent of switch radix, the switch exhibits low-loss performance even for large-scale switches. The first chapter of this thesis covers the design, fabrication, and characterization of a small-scale 4 x 4 switch which, was then, incorporated in a successful network demonstration, showing sub-microsecond optical circuit switching. The switch was also fully packaged to further prove the feasibility of the technology. Next, a novel switch architecture, based on multi-level bus waveguides to eliminate in-plane waveguide crossings, is presented. This design enables lower crosstalk, optical loss, and more broadband performance at the expense of greater fabrication complexity. To demonstrate the new architecture, a 32 x 32 switch was fabricated using a wafer bonding process. The resulting device exhibited 4.6 dB maximum on-chip loss, less than -80 dB crosstalk and 1.5 μs and 0.9 μs switch ON- and OFF-time, respectively. Finally, a silicon photonic switch was heterogeneously integrated with high-voltage driver chiplets to enable scalable electrical packaging. An application-specific integrated circuit, comprised of a 32 x 32 array of high-voltage driver cells that match the optical switch unit cells, was designed and successfully flip-chip-bonded to a 128 x 128 photonic integrated circuit switch chip. The resulting 32 x 32 packaged switch had 99.7 % switch cell yield and average switch-ON and switch-OFF time of 0.81 μs and 0.41 μs, respectively.

Advisors: Ming C. Wu

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BibTeX citation:

@phdthesis{Henriksson:31753,
    Author= {Henriksson, Johannes},
    Editor= {Wu, Ming C.},
    Title= {Large-Scale Silicon Photonic Switches with Sub-Microsecond Switching Time},
    School= {EECS Department, University of California, Berkeley},
    Year= {2025},
    Number= {UCB/},
    Abstract= {Fueled by growing demand for cloud computing applications, such as machine learning, the scale, bandwidth, and power consumption of data center networks continue to increase, and with it, a demand for novel network technologies and architectures. One such emerging technology is the optical circuit switch, which can increase the performance, flexibility, and power consumption of data centers.
The optical circuit switch presented here is an integrated, non-blocking, switch built on a scalable silicon photonics platform. The switching mechanism is based on vertically movable adiabatic coupler waveguides controlled by micro-electromechanical-system actuators, enabling sub-microsecond switching time. By using a crossbar architecture, where light traverses an ON-state switch unit cell only once, independent of switch radix, the switch exhibits low-loss performance even for large-scale switches.
The first chapter of this thesis covers the design, fabrication, and characterization of a small-scale 4 x 4 switch which, was then, incorporated in a successful network demonstration, showing sub-microsecond optical circuit switching. The switch was also fully packaged to further prove the feasibility of the technology.
Next, a novel switch architecture, based on multi-level bus waveguides to eliminate in-plane waveguide crossings, is presented. This design enables lower crosstalk, optical loss, and more broadband performance at the expense of greater fabrication complexity. To demonstrate the new architecture, a 32 x 32 switch was fabricated using a wafer bonding process. The resulting device exhibited 4.6 dB maximum on-chip loss, less than -80 dB crosstalk and 1.5 μs and 0.9 μs switch ON- and OFF-time, respectively. 
Finally, a silicon photonic switch was heterogeneously integrated with high-voltage driver chiplets to enable scalable electrical packaging. An application-specific integrated circuit, comprised of a 32 x 32 array of high-voltage driver cells that match the optical switch unit cells, was designed and successfully flip-chip-bonded to a 128 x 128 photonic integrated circuit switch chip. The resulting 32 x 32 packaged switch had 99.7 % switch cell yield and average switch-ON and switch-OFF time of 0.81 μs and 0.41 μs, respectively.},
}

EndNote citation:

%0 Thesis
%A Henriksson, Johannes 
%E Wu, Ming C. 
%T Large-Scale Silicon Photonic Switches with Sub-Microsecond Switching Time
%I EECS Department, University of California, Berkeley
%D 2025
%8 December 1
%@ UCB/
%F Henriksson:31753