Empirical model of optical sensing via spectral shift of circular Bragg phenomenon

TL;DR

This paper develops an empirical model for optical sensing using the spectral shift of the circular Bragg phenomenon in chiral sculptured thin films, demonstrating high sensitivity to infiltrated fluid refractive index changes.

Contribution

It introduces an empirical model linking the circular Bragg phenomenon in CSTFs to fluid refractive index sensing, including effects of a twist defect.

Findings

Spectral shifts are highly sensitive to fluid refractive index changes.

Presence of a twist defect creates a spectral hole useful for sensing.

CSTFs show promise as optical sensors for fluid detection.

Abstract

Setting up an empirical model of optical sensing to exploit the circular Bragg phenomenon displayed by chiral sculptured thin films (CSTFs), we considered a CSTF with and without a central twist defect of $\pi/2$ radians. The circular Bragg phenomenon of the defect-free CSTF, and the spectral hole in the co-polarized reflectance spectrum of the CSTF with the twist defect, were both found to be acutely sensitive to the refractive index of a fluid which infiltrates the void regions of the CSTF. These findings bode well for the deployment of CSTFs as optical sensors.