Analytical study of optical dielectric interfaces for sensing applications

TL;DR

This paper analytically derives formulas for the sensitivity of optical dielectric interface sensors, revealing how device parameters and angles influence their ability to detect small refractive index changes.

Contribution

It provides explicit formulas for sensor sensitivity, clarifying the effects of incidence angle and polarization modes, advancing understanding of optical sensing mechanisms.

Findings

Sensitivity increases near the angle of total reflection.

P mode sensitivity exceeds S mode near the critical angle.

Explicit formulas improve sensor design accuracy.

Abstract

Dynamic optical sensors, as those based on the reflectivity of isotropic dielectrical interfaces, can be useful for measuring small changes in the refractive index of fluid media. Exact and approximated explicit formulas for their sensitivity are developed. These expressions clarify the influence of each of the constructive parameters of the device, both in partial and in total reflection. It is analytically found that sensitivities are always greater when the angle of incidence approaches the angle of total reflection. It is also demonstrated that close to the critical angle for both types of reflection, the sensitivity of the p mode is greater than that of the s mode.