Nanoscale atomic suspended waveguides for improved vapour coherence times and optical frequency referencing

There has recently been growing interest in integrating and miniaturizing vapour cells to reduce cost, size and power consumption. Hereby we provide a new paradigm in chip-scale-integrated vapour cells by experimentally demonstrating the nanoatomic suspended waveguide, which introduces a nanoscale silicon nitride waveguide suspended in rubidium vapour. By doing so, the properties of the optical modes and the light–vapour interactions are controlled by the waveguide dimensions and can be tailored precisely for specific applications. Compared with previously published atomic cladded waveguides, our new device allows for a substantial reduction of Doppler and transit time broadening and improves the vapour coherence time. Furthermore, it practically eliminates the van der Waals shift and drastically reduces the light shift by two orders of magnitude. We have shown the usefulness of the device as a frequency reference with instability below 50 kHz. The demonstrated approach could also be used for other diverse applications that benefit from accurate and precise light–vapour applications, for example, magnetometry, quantum storage, atomic clocks, high-spatial-resolution field sensors and all-optical switching.