FFPs: Fiber Fabry-Perot microcavities

Progress in quantum technologies critically depends on the progress of optical cavities. This has spurred the development of optical microcavities. Our group has developed a fiber-based Fabry-Perot microcavity (FFP) with exceptional properties. Its laser machined-mirrors enable extremely high finesse (F>100.000), combined with microscopic waist and mode volume. Moreover, our FFPs are fiber coupled by design and feature open access to the optical mode. With these unique properties, they are having a large impact in quantum technologies and beyond. Originally designed for our experiments on high-fidelity atomic qubit detection and cavity QED with Bose-Einstein condensates, FFPs have been adopted by dozens of research laboratories, with many of whom we collaborate. They have been combined with virtually all quantum emitters, ranging from ultracold atoms and ions to diamond NV centers, quantum dots and carbon nanotubes, and are used for cavity optomecanics with nanorods, membranes, and now superfluid helium. They have been used in a miniature Raman spectrometer, and have given rise to a new form of scanning probe microscopy. In our own research, we currently use them for spin squeezing in atomic clocks and quantum simulations with long-range interactions, and we are developing a miniature greenhouse gas analyzer in collaboration with the startup company Mirega.