Suspended silicon nitride thin films with enhanced and electrically tunable reflectivity

TL;DR

This paper demonstrates the fabrication of suspended silicon nitride membranes with a patterned grating that exhibits a Fano resonance, enabling electrically tunable reflectivity from 10% to 78% at near-infrared wavelengths.

Contribution

It introduces a method to create electrically tunable, high-reflectivity silicon nitride membranes with a patterned grating for optical applications.

Findings

Reflectivity increased from 10% to 78% at 937 nm.

Fano resonance observed in transmission spectrum.

Spectral shift of 0.23 nm under applied force.

Abstract

We report on the realization of silicon nitride membranes with enhanced and electrically tunable reflectivity. A subwavelength one-dimensional grating is directly patterned on a suspended 200 nm-thick, high stress commercial film using electron beam lithography. A Fano resonance is observed in the transmission spectrum of TM polarized light impinging on the membrane at normal incidence, leading to an increase in its reflectivity from 10% to 78% at 937 nm. The observed spectrum is compared to the results of rigorous coupled wave analysis simulations based on measurements of the grating transverse profile through localized cuts of the suspended film with a Focused Ion Beam. By mounting the membrane chip on a ring piezoelectric transducer and applying a compressive force to the substrate we subsequently observe a shift of the transmission spectrum by 0.23 nm.