Ultra-low-crosstalk Silicon Switches Driven Thermally and Electrically

TL;DR

This paper introduces two silicon Mach-Zehnder interferometer switches with ultra-low crosstalk below -40 dB, achieved through device and circuit optimization, including novel use of self-heating effects for phase control, suitable for high-speed data transmission.

Contribution

The paper presents the first use of self-heating in carrier-injection MZI switches to create phase shifters with matched insertion loss, significantly reducing crosstalk in silicon photonic switches.

Findings

Achieved crosstalk below -40 dB in both thermo-optic and electro-optic switches.

Demonstrated high-speed data transmission at 50 Gb/s with high fidelity.

On-chip losses of less than 5 dB (T-O) and 8.5 dB (E-O).

Abstract

Silicon photonic switches are widely considered as a cost-effective solution for addressing the ever-growing data traffic in datacenter networks, as they offer unique advantages such as low power consumption, low latency, small footprint and high bandwidth. Despite extensive research efforts, crosstalk in large-scale photonic circuits still poses a threat to the signal integrity. In this paper, we present two designs of silicon Mach-Zehnder Interferometer (MZI) switches achieving ultra-low-crosstalk, driven thermally and electrically. Each switch fabric is optimized at both the device and circuit level to suppress crosstalk and reduce system complexity. Notably, for the first time to the best of our knowledge, we harness the inherent self-heating effect in a carrier-injection-based MZI switch to create a pair of phase shifters that offer arbitrary phase differences. Such a pair of phase shifters induces matched insertion loss at each arm, thus minimizing crosstalk. Experimentally, an ultra-low crosstalk ratio below -40 dB is demonstrated for both thermo-optic (T-O) and electro-optic (E-O) switches. The T-O switch exhibits an on-chip loss of less than 5 dB with a switching time of 500 microseconds, whereas the E-O switch achieves an on-chip loss as low as 8.5 dB with a switching time of under 100 ns. In addition, data transmission of a 50 Gb/s on-off keying signal is demonstrated with high fidelity on the E-O switch, showing the great potential of the proposed switch designs.