Open-access microcavities: high stability without dedicated mechanical low-pass filter in closed-cycle cryostats

TL;DR

This paper demonstrates a highly stable open-access microcavity operating at 4 K in a closed-cycle cryostat without the need for dedicated mechanical filters, enabling flexible optical tuning and polarization control.

Contribution

It introduces a novel microcavity design that achieves high stability in noisy cryogenic environments without specialized damping components.

Findings

Achieved 5.7 pm rms stability in quiet cycle

Achieved 10.6 pm rms stability in full cycle

Operates effectively at 4 K with free-space optical access

Abstract

Open-access optical microcavities are Fabry-Perot type cavities consisting of two micrometer-size mirrors, separated by an air (or vacuum) gap typically of a few micrometers. Compared to integrated microcavities, this configuration is more flexible as the relative position of the two mirrors can be tuned, allowing to change on demand parameters such as cavity length and mode volume, and to select specific transverse cavity modes. These advantages come at the expense of mechanical stability of the cavity itself, which is particularly relevant in noisy closed-cycle cryostats. Here we show an open-access optical microcavity based on scanning-probe microscope design principles. When operated at 4 K in a tabletop optical closed-cycle cryostat without any dedicated low-pass filter, we obtain stabilities of 5.7 and 10.6 pm rms in the quiet and full period of the cryocooler cycle, respectively. Our device has free-space optical access, essential for instance for full polarization control.