Slow thermo-optomechanical pulsations in suspended 1D photonic crystal nanocavities

TL;DR

This paper explores the nonlinear thermo-optical behavior of suspended 1D photonic crystal nanocavities, revealing self-sustained pulsations at low power levels and modeling their complex dynamics through a simplified mathematical framework.

Contribution

It demonstrates thermo-optical nonlinearities and pulsations at unprecedentedly low powers, and introduces a simplified model explaining the observed dynamics in these nanocavities.

Findings

Thermo-optical nonlinearities observed at input powers as low as 2 μW.

Emergence of self-sustained pulsations with periods of several seconds.

Theoretical model reproduces experimental behaviors and explains dynamics via a 1D critical manifold.

Abstract

We investigate the nonlinear optical response of suspended 1D photonic crystal nanocavities fabricated on a silicon nitride chip. Strong thermo-optical nonlinearities are demonstrated for input powers as low as $2\,\mu\text{W}$ and a self-sustained pulsing regime is shown to emerge with periodicity of several seconds. As the input power and laser wavelength are varied the temporal patterns change in period, duty cycle and shape. This dynamics is attributed to the multiple timescale competition between thermo-optical and thermo-optomechanical effects and closely resembles the relaxation oscillations states found in mathematical models of neuronal activity. We introduce a simplified model that reproduces all the experimental observations and allows us to explain them in terms of the properties of a 1D critical manifold which governs the slow evolution of the system.