Cavity ring-up spectroscopy for dissipative and dispersive sensing in a whispering gallery mode resonator

TL;DR

This paper explores cavity ring-up spectroscopy (CRUS) in whispering gallery mode resonators, demonstrating its potential for rapid, transient sensing of dispersive and dissipative effects through peak height measurements, verified experimentally.

Contribution

It provides analytical solutions for CRUS using coupled mode equations and experimentally verifies the relationships between key parameters in high-Q silica microspheres.

Findings

CRUS can detect dispersive and dissipative effects transiently.

Peak height of CRUS signal correlates with sensing parameters.

Experimental verification confirms theoretical predictions.

Abstract

In whispering gallery mode resonator sensing applications, the conventional way to detect a change in the parameter to be measured is by observing the steady state transmission spectrum through the coupling waveguide. Alternatively, cavity ring-up spectroscopy (CRUS) sensing can be achieved transiently. In this work, we investigate CRUS using coupled mode equations and find analytical solutions with a large spectral broadening approximation of the input pulse. The relationships between the frequency detuning, coupling gap and ring-up peak height are determined and experimentally verified using an ultrahigh \textit{Q}-factor silica microsphere. This work shows that distinctive dispersive and dissipative transient sensing can be realised by simply measuring the peak height of the CRUS signal, which might improve the data collection rate.