Limits to superweak amplification of beam shifts

TL;DR

This paper investigates the limits of superweak amplification of beam shifts in optics, deriving formulas for maximum shifts near critical angles and showing these are bounded by higher-order reflection effects.

Contribution

It provides a theoretical analysis of the maximum achievable beam shifts near specific angles, including the Brewster angle, highlighting fundamental limits to superweak amplification.

Findings

Maximum beam shifts are limited by higher-order reflection effects.

Derived formulas include the Brewster angle and other critical angles.

Amplification is constrained despite near-zero transmission conditions.

Abstract

The magnitudes of beam shifts (Goos-H\"anchen and Imbert-Fedorov, spatial and angular) are greatly enhanced when a reflected light beam is postselected by an analyzer, by analogy with superweak measurements in quantum theory. Particularly strong enhancements can be expected close to angles at which no light is transmitted for a fixed initial and final polarizations. We derive a formula for the angular and spatial shifts at such angles (which includes the Brewster angle), and we show that their maximum size is limited by higher-order terms from the reflection coefficients occurring in the Artmann shift formula.