Light-induced magnetic trapping for cold alkali atoms using a combined optical tweezers and nanofibre platform

Abstract: We present a magnetic trapping method for cold $^{87}$Rb atoms, utilising the light-induced magnetic fields from the evanescent field of an optical nanofibre (ONF) in conjunction with an optical tweezers. We calculate and plot the trapping potentials for both Gaussian and Laguerre-Gaussian modes of the optical tweezers, and quasi-linear polarisation of the ONF-guided field. Based on the optical powers in the tweezers beam and the ONF-guided mode, we analyse the trap depths and the distances of the trap minima from the surface of the nanofibre. We show that, by controlling the powers in both of the optical fields, one can vary the trap position over a few hundreds of nanometres, while also influencing the trap depth and trap frequencies. Such control over atom position is essential both for studying distance-dependent effects on atoms trapped near dielectric surfaces, and minimising these effects for quantum technology applications.