# Co-Design of BW-Enhanced Dual-Path Driver and Segmented Microring Modulator for Energy Efficient Si-Photonic Transmitters

## TL;DR

This paper introduces a new design for silicon photonic transmitters that improves bandwidth and energy efficiency for high-speed optical communication.

## Contribution

A tunable co-design approach for dual-path drivers and segmented microring modulators to enhance bandwidth and extinction ratio.

## Key findings

- The 3 dB electro-optical bandwidth improved from ~50 to >70 GHz.
- A 200 Gb/s PAM4 optical eye diagram showed an open eye with 1.44 pJ/bit energy efficiency.
- The extinction ratio increased from 2 dB to 4.1 dB.

## Abstract

Artificial intelligence computing systems increasingly demand high-bandwidth, high-extinction-ratio, chip-to-chip optical transceivers. Silicon microring modulators (MRMs) are attractive for such transmitters due to their compact footprint and wavelength-division multiplexing capability. However, for a specified extinction ratio, the optical bandwidth for high-Q MRMs and the driver’s RC time constant prevent conventional single-segment MRM drivers from supporting 100 GBaud class PAM4 transmission. This work presents a broadband driver exploiting the feedforward technique for dual-segment MRMs. It extends electro-optical bandwidth while maintaining a high Q-factor and extinction ratio. The input signal is split into low- and high-frequency components that drive the long and short segments of the MRM, respectively. The long segment uses a broadband low-pass driver, whereas the short segment employs a driver with a programmable bandpass response near the Nyquist frequency. The design space is obtained from an equivalent electro-optical model under constant group-delay constraints. Simulations at 1310 nm show that the 3 dB electro-optical bandwidth improves from ~50 to >70 GHz and that a 200 Gb/s PAM4 optical eye diagram exhibits an open eye; the energy efficiency is 1.44 pJ/bit, and the extinction ratio improves from 2 dB to 4.1 dB. The proposed technique provides a tunable electro-optical co-design approach for high-bandwidth-density, high-extinction-ratio silicon photonic transmitters.