Quantum entanglement enabled ellipsometer for phase retardance measurement

TL;DR

This paper introduces a quantum ellipsometer combining entangled photons with classical methods, achieving nanometer-scale accuracy in phase retardance measurement under extremely low light conditions, useful for sensitive samples.

Contribution

The work presents the first quantum ellipsometer that integrates entangled photon sources with classical ellipsometry for enhanced low-light measurement precision.

Findings

Achieves nanometer-scale accuracy at low incident light intensity

Maintains stability within 1% across tested specimens

Enables measurement of photosensitive and biological samples

Abstract

An ellipsometer is a vital precision tool used for measuring optical parameters with wide applications in many fields, including accurate measurements in film thickness, optical constants, structural profiles, etc. However, the precise measurement of photosensitive materials meets huge obstacles because of the excessive input photons, therefore the requirement of enhancing detection accuracy under low incident light intensity is an essential topic in the precision measurement. In this work, by combining a polarization-entangled photon source with a classical transmission-type ellipsometer, the quantum ellipsometer with the PSA (Polarizer-Sample-Analyzer) and the Senarmount method is constructed firstly to measure the phase retardation of the birefringent materials. The experimental results show that the accuracy can reach to nanometer scale at extremely low input intensity, and the stability are within 1% for all specimens tested with a compensator involved. Our work paves the way for precision measurement at low incident light intensity, with potential applications in measuring photosensitive materials, active-biological samples and other remote monitoring scenarios.