Silicon microcavity arrays with open access and a finesse of half a million

TL;DR

This paper reports the fabrication of silicon microcavity arrays with extremely high finesse and low loss, enabling advanced optical applications and strong light-matter interactions.

Contribution

It introduces lithographically aligned silicon microcavities with ultra-smooth surfaces and high finesse, pushing the limits of optical resonator technology.

Findings

Finesse greater than 500,000 achieved

Mode volume of 330 femtoliters at 1550 nm

Large arrays of high-quality microcavities fabricated

Abstract

Optical resonators are increasingly important tools in science and technology. Their applications range from laser physics, atomic clocks, molecular spectroscopy, and single-photon generation to the detection, trapping and cooling of atoms or nano-scale objects. Many of these applications benefit from strong mode confinement and high optical quality factors, making small mirrors of high surface-quality desirable. Building such devices in silicon yields ultra-low absorption at telecom wavelengths and enables integration of micro-structures with mechanical, electrical and other functionalities. Here, we push optical resonator technology to new limits by fabricating lithographically aligned silicon mirrors with ultra-smooth surfaces, small and wellcontrolled radii of curvature, ultra-low loss and high reflectivity. We build large arrays of microcavities with finesse greater than F = 500,000 and a mode volume of 330 femtoliters at wavelengths near 1550 nm. Such high-quality micro-mirrors open up a new regime of optics and enable unprecedented explorations of strong coupling between light and matter.