Ultra-compact and wide-spectrum-range thermo-optic switch based on silicon coupled photonic crystal microcavities

TL;DR

This paper presents a compact silicon-based thermo-optic switch utilizing coupled photonic crystal microcavities, achieving wide-spectrum operation, high extinction ratio, and low insertion loss, suitable for integrated photonic circuits.

Contribution

It introduces a novel design of a thermo-optic switch with coupled photonic crystal microcavities that offers a wider operational spectrum and improved performance over traditional microring resonators.

Findings

6 nm-wide flat-bottom resonance enabling broad spectrum operation

20 dB optical extinction ratio achieved

Low on-chip loss of 1 dB

Abstract

We design, fabricate, and experimentally demonstrate a compact thermo-optic gate switch comprising a 3.78 um-long coupled L0-type photonic crystalmicrocavities on a silicon-on-insulator substrate. A nanohole is inserted in the center of each individual L0 photonic crystalmicrocavity. Coupling between identical microcavities gives rise to bonding and anti-bonding states of the coupled photonic molecules. The coupled photonic crystalmicrocavities are numerically simulated and experimentally verified with a 6 nm-wide flat-bottom resonance in its transmission spectrum, which enables wider operational spectrum range than microring resonators. An integrated micro-heater is in direct contact with the silicon core to efficiently drive the device. The thermo-optic switch is measured with an optical extinction ratio of 20 dB, an on-off switching power of 18.2 mW, a thermo-optic tuning efficiency of 0.63 nm/mW, a rise time of 14.8 us, and a fall time of 18.5 us. The measured on-chip loss on the transmission band is as low as 1 dB.