# Analytical Fresnel laws at generic curved interfaces

## TL;DR

This paper derives new Fresnel laws for curved interfaces, extending classical ray optics to accurately describe light reflection in complex micro- and nano-optical structures with curved boundaries.

## Contribution

It provides the first analytical Fresnel laws for concavely curved interfaces, addressing a key gap in optical theory for curved boundary conditions.

## Key findings

- Derived Fresnel laws for concave interfaces.
- Showed deviations from classical laws at micro-scale curvature.
- Enables accurate modeling of light in complex optical structures.

## Abstract

Fresnel laws, the quantitative information of the amount of light that is reflected from a planar interface in dependence on its angle of incidence, are at the core of ray optics. However, these formulae do not hold at curved interfaces and deviations are appreciable when wavelength and radius of curvature are comparable. This is of particular interest for optical microcavities that play an important role in many modern research fields and applications such as microlasers. Their convexly curved interfaces modify Fresnel's law in a characteristic manner: the onset of total internal reflection is shifted to angles larger than the critical angle. Here, we derive the missing Fresnel laws for concavely curved refractive index boundaries, enabling the analytical description of light in complex mesoscopic optical structures that will be important in future nano- and microphotonic applications.

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Source: https://tomesphere.com/paper/1904.05663