Quantum Limits and Robustness of Nonlinear Intracavity Absorption Spectroscopy

TL;DR

This paper explores the fundamental and practical limits of nonlinear intracavity absorption spectroscopy, demonstrating that while nonlinear media do not surpass quantum limits, they offer increased robustness against technical noise, aiding spectrometer design.

Contribution

It provides a comparative analysis of nonlinear and linear intracavity spectroscopy methods, highlighting the robustness of nonlinear techniques against technical noise.

Findings

Nonlinear methods do not surpass quantum-limited sensitivity of empty cavities.

Nonlinear techniques are more robust against certain technical noise sources.

Potential applications in designing spectrometers for non-ideal environments.

Abstract

We investigate the limits of intracavity absorption spectroscopy with nonlinear media. Using a common theoretical framework, we compare the detection of a trace gas within an undriven cavity with gain near and above threshold, a driven cavity with gain kept just below threshold, and a cavity driven close to the saturation point of a saturable absorber. These phase-transition-based metrology methods are typically quantum-limited by spontaneous emission, and we compare them to the empty cavity shotnoise-limited case. Although the fundamental limits achievable with nonlinear media do not surpass the empty cavity limits, we show that nonlinear methods are more robust against certain technical noise models. This recognition may have applications in spectrometer design for devices operating in non-ideal field environments.