A study of thermally-induced optical bistability and the role of surface treatments in Si-based mid-infrared photonic crystal cavities

TL;DR

This paper investigates thermal optical bistability in silicon-based mid-infrared photonic crystal cavities, demonstrating how surface treatments can improve quality factors and eliminate bistability.

Contribution

It provides new insights into the thermal origin of optical bistability and shows how surface treatments and annealing can enhance cavity performance and suppress bistability.

Findings

Thermal optical bistability observed at 4.5 μm in Si photonic cavities.

Surface treatments increase Q-factor from 11,500 to 29,300.

Annealing in N2 eliminates optical bistability.

Abstract

We report the observation of optical bistability in Si-based photonic crystal cavities operating around 4.5 \mum. Time domain measurements indicate that the source of this optical bistability is thermal, with a time constant on the order of 5 \mus. Quality (Q) factor improvement is shown by the use of surface treatments (wet processes and annealing), resulting in an increase of Q-factor from 11,500 to 29,300 at 4.48 \mum. After annealing in a N2 environment, optical bistability is no longer seen in our cavities.