A highly stable and fully tunable open microcavity platform at cryogenic temperatures

Open-access microcavities are a powerful tool to enhance light–matter interactions for solid-state quantum and nanosystems key advance applications in technologies. For this purpose, the cavities should simultaneously meet two conflicting requirements—full tunability cope with spatial spectral inhomogeneities of material highest stability under operation cryogenic environment maintain resonance conditions. To tackle challenge, we have developed fully tunable, open-access, fiber-based Fabry–Pérot microcavity platform that can be operated increased noise levels closed-cycle cryostat. It comprises custom-designed monolithic micro- nanopositioning elements up mm-scale travel range achieve passive cavity length at low temperature only 15 pm rms cryostat 5 more quiet flow This further improved by active stabilization, even higher is obtained direct mechanical contact between mirrors, yielding 0.8 during phase cryocooler. The provides high finesse small mode volume strong enhancement interactions, opening novel possibilities experiments great variety nanomaterials.