Low-parasitic-resistance and fabrication-tolerant silicon microring modulators operating beyond 100 GHz

Silicon microring modulators (MRMs) are promising for compact, energy-efficient optical interconnects, yet their electro-optic bandwidth is constrained by the RC time constant, and their resonance wavelength is highly susceptible to fabrication variations. In this work, we present a carrier-depletion MRM that mitigates these issues by integrating an adiabatic transition with a widened low-parasitic-resistance region. The design extends the low-resistance cross-section over 61% of the cavity circumference, reducing the junction series resistance to 36.9 ohms, which is 35.9% lower than conventional designs. Across eight dies, the resonance wavelength spread is reduced from 3.58 to 1.07 nm. The modulator exhibits a measured 3-dB electro-optic bandwidth exceeding 100 GHz over a bias range of −1 to −5 V. It supports 144 Gbps NRZ and 224 Gbps PAM-4, with the latter demonstrating a bit error rate below the 7% hard-decision forward-error-correction threshold. Moreover, the device can operate in a self-bias mode at 0 V bias, achieving 128 Gbps NRZ with an estimated energy consumption of 0.861 fJ/bit, while depletion-mode operation consumes 8.878 fJ/bit.