For future atom-photonic devices, the incoupling method is expected to become the main bottleneck in the scal ing of the number of devices, as current devices use side-coupling, which is restricted to the sample edges. This paper describes how light from above is coupled directly from free space into a freestanding membrane of 220 nm thin silicon nitrite (Si3N4) with surface grating couplers. The design for these couplers is modeled, captured in an elegant design formula, and experimentally tested. A coupling efficiency of 12% makes experimental coupling to an array of atom-photonic devices possible. The elegant design formula makes grating design straightforward for all-dielectric materials and wavelengths. For this formula, determination of the correct effective index of t he specific waveguide mode inside the grating layer is essential.

Atomic and Molecular Physics, and Optics, Statistical and Nonlinear Physics
J. Opt. Soc. Am. B

van Lange, A.J, Lof, A, & van Oosten, D. (2020). Non-contact surface grating coupling for arrays of atom–photonic devices. J. Opt. Soc. Am. B, 37(4), 921–926. doi:10.1364/josab.384110