Noise Properties of Coherent Perfect Absorbers and Critically-coupled Resonators

TL;DR

This paper analyzes the noise characteristics of coherent perfect absorbers and critically-coupled resonators, focusing on quantum and thermal noise effects near resonance, and evaluates their potential as sensitive background-free detectors.

Contribution

It provides a detailed theoretical analysis of noise limits in coherent perfect absorbers, highlighting their performance constraints and potential as highly sensitive detectors.

Findings

Quantum shot noise dominates near resonance at zero temperature.

Noise vanishes exactly at the resonance frequency.

Sensitivity is limited by finite bandwidth effects.

Abstract

The performance of a coherent perfect absorber (time-reversed laser) is limited by quantum and thermal noise. At zero temperature, the quantum shot noise dominates the signal for frequencies close to the resonance frequency, and both vanish exactly at the resonance frequency. We compute the sensitivity of the absorbing cavity as a background-free detector, limited by finite signal or detector bandwidth.