Investigation on high-speed ring modulators

As increasing demand on high-speed transceivers for CPO applications, e.g. 400G per lane, we want to look for the solutions and designs of ring modulator operating beyond 100GHz bandwidth. There is a clear trade-off between efficiency (transmitter penalty, TP) and bandwidth observed [1], but high bandwidth beyond 100GHz is challenging even if we can sacrifice the efficiency.

We have some designs with low Q-factor ring modulators (expecting higher BW), so the task of internship will be

1. Verify and measure (if needed) the various ring modulator design for high-speed operation in different operating points (e.g. bias, detuning wavelength, etc)
   Required skill: analysis on measured data (Python), understanding of ring odu
2. Characterize and model the fabricated device’s performance, and find the limitation of the device where the bandwidth limitation comes from
   Required skill: understanding of ring modulator’s behavior in model (theoretical understanding), fitting the measured data and compare to the theoretical equation (Python)
3. (If available) Looking for the solution/design for high-speed ring modulator beyond 100GHz
   Required skill: TCAD, Lumerical simulation for design, Layout skill if needed

[1] Minkyu Kim, Yoojin Ban, Filippo Ferraro, David Coenen, Natarajan Rajasekaran, Peter Verheyen, Rafal Magdziak, Huseyin Sar, Peter De Heyn, Dimitrios Velenis, Philippe Absil, and Joris Van Campenhout, "O-Band Silicon Ring Modulators With Highly Efficient Electro- and Thermo-Optic Modulation," J. Lightwave Technol. 43, 1328-1334 (2025)