Tunable linear-optical phase amplification

TL;DR

This paper introduces a method for nonlinear phase amplification using linear optics, enabling tunable phase shifts that significantly enhance interferometric sensitivity.

Contribution

It presents a novel principle of linear-optical phase amplification and demonstrates an experimentally tunable phase shifter with improved interferometric performance.

Findings

Achieved over twentyfold increase in intensity-phase slope

Demonstrated tunable phase enhancement parameter

Validated the concept with experimental realization

Abstract

We combine lossless, phase-only transformations with fully-transmitting linear-optical scatterers to define the principle of linear-optical phase amplification. This enables a physical phase shift $\phi$ to be nonlinearly mapped to a new space $\gamma(\phi)$ using linear optics, resulting in a completely general and enhanced phase shifter that can replace any standard one. A particular phase amplifier is experimentally realized, allowing the phase enhancement parameter $d\gamma/d\phi$ to be continuously tuned. Placing this enhanced phase shifter in one arm of a Mach-Zehnder interferometer led to an intensity-phase slope more than twenty times steeper than what can be obtained with its unamplified counterpart.