Cavity buildup dispersion spectroscopy

TL;DR

Cavity buildup dispersion spectroscopy (CBDS) offers a novel, highly accurate method for measuring ultrahigh-fidelity absorption spectra by encoding dispersive shifts in a cavity's transient response, reducing nonlinearities and enabling single-shot measurements.

Contribution

This paper introduces CBDS, a new technique that improves accuracy and reduces nonlinearities in dispersion spectroscopy by using cavity transient responses for measurement.

Findings

CBDS achieves 50 times less susceptibility to nonlinearities.

CBDS enables single-shot dispersion measurements.

Accuracy limited by frequency standard, speed by cavity round-trip time.

Abstract

Measurements of ultrahigh-fidelity absorption spectra can help validate quantum theory, engineer ultracold chemistry, and remotely sense atmospheres. Recent achievements in cavity-enhanced spectroscopy using either frequency-based dispersion or time-based absorption approaches have set new records for accuracy with uncertainties at the sub-per-mil level. However, laser scanning5 or susceptibility to nonlinearities limits their ultimate performance. Here we present cavity buildup dispersion spectroscopy (CBDS) in which the dispersive frequency shift of a cavity resonance is encoded in the cavity's transient response to a phase-locked non-resonant laser excitation. Beating between optical frequencies during buildup exactly localizes detuning from mode center, and thus enables single-shot dispersion measurements. CBDS yields an accuracy limited by the chosen frequency standard, a speed limited by the cavity round-trip time, and is currently 50 times less susceptible to detection nonlinearity compared to intensity-based methods. The universality of CBDS shows promise for improving fundamental research into a variety of light-matter interactions.