Magic wavelengths of ⁸⁸Sr intercombination transition for interfacing with optical ring resonators

Intrinsic properties of strontium-88 atoms make it a strong candidate for future atomtronic applications. Aluminum nitride optical ring resonators offer a practical platform to interface light with strontium atoms due to their ultra-high Q factors and large evanescent fields nearby the dominant 461-nm atomic transition. Finely tuned intensities of 400-500-nm attractive and repulsive wavelengths can generate trapping wells hundreds of nanometers away from the device surface. When loading from the magneto-optical trap (MOT), the evanescent fields can cause position- and level-dependent energy shifts on the atoms, thus detuning their spectrum from the MOT cooling transition and reducing trap loading efficiencies. However, utilizing attractive and repulsive magic wavelength traps of the narrow-line cooling transition can mitigate this effect and improve loading efficiencies. Here, we present spectroscopic measurements of an attractive magic wavelength of ⁸⁸Sr at 473.117(15) nm and a theoretically predicted repulsive magic wavelength at 435.825 nm. Various optical ring resonator designs with high Q factors at these wavelengths provide viable platforms for interfacing strontium with nanophotonic chips.