Measuring the true quality factor of an ultrafast photonic microcavity: homogeneous versus inhomogeneous broadening

TL;DR

This paper measures the true quality factor of an ultrafast photonic microcavity using time-resolved techniques, revealing the impact of inhomogeneous broadening on the resonance linewidth.

Contribution

It demonstrates a method to distinguish between homogeneous and inhomogeneous broadening effects in microcavity quality factor measurements.

Findings

Measured photon storage time of 0.78 ps in the microcavity.

Found the quality factor from time-resolved data is 1500.

Identified inhomogeneous broadening as the cause of discrepancy in linewidth measurements.

Abstract

We have measured time-resolved the photon storage time and the quality factor of an ultrafast photonic cavity using an autocorrelator. The cavity consists of a $\lambda$-thick GaAs layer sandwiched between GaAs/AlAs distributed Bragg reflectors and resonates at 985 nm wavelength. The inverse relative linewidth measured with white light reflectivity is 830, while the quality factor obtained from the time resolved measurements is 1500. The photon storage time in the cavity is 0.78 ps. We show that the difference between the quality factor and the inverse relative linewidth results from inhomogeneous broadening of the microcavity resonance due to a spatial gradient in the cavity layer.