Thin liquid film as an optical nonlinear-nonlocal medium and memory element in integrated optofluidic reservoir computer

TL;DR

This paper explores the use of a thin liquid film in integrated photonics as a nonlinear, nonlocal medium and optical memory element, enabling novel light-matter interactions and reservoir computing capabilities.

Contribution

It introduces a new optofluidic platform with thermocapillary-driven effects that enable optical phase modulation and memory functions in integrated photonics.

Findings

Self-induced phase change in waveguides due to liquid film deformation

Nonlocal interactions between adjacent waveguides

Demonstration of reservoir computing using the liquid film as a nonlinear, memory element

Abstract

Understanding light-matter interaction enables harnessing physical effects to translate into new capabilities realized in modern integrated photonics platforms. Here, we present the design and characterization of optofluidic components in integrated photonics platform, and numerically predict a series of novel physical effects which rely on thermocapillary-driven interaction between waveguide modes to topography changes of optically thin liquid dielectric film. Our results indicate that this coupling introduces substantial self-induced phase change in a single channel waveguide, transmittance through Bragg grating waveguide and nonlocal interaction between adjacent waveguides. We then employ the self-induced phase change together with the inherent built-in finite relaxation time of the liquid film, to demonstrate that its light-driven deformation can serve as a reservoir computer capable to perform digital and analog tasks, where the gas-liquid interface operates both as a nonlinear actuator and as an optical memory element.