Silicon Nitride-Photonics-Enabled Optical Pumping for Optically Pumped Magnetometer

Abstract

Discrete optical system in optically pumped magnetometers (OPMs) presents a significant challenge to their integration into high-spatial-resolution magnetic field detection. Here, the electron spin polarization of ${}^{87}\mathrm{Rb}$ atoms using a fiber-coupled silicon nitride (${\mathrm{Si}}_3{\mathrm{N}}_4$) photonic integrated circuit (PIC) is demonstrated, by the way of delivering arrayed elliptically polarized light (EPL) into a vapor cell. Specifically, the photonic integrated circuit (PIC) transforms fiber-coupled 795 nm pump light via optical waveguides to eight divergent free-space beams, simultaneously converting linear polarized light (LPL) into EPL with an average polarization conversion efficiency of 71%. The ${\mathrm{Si}}_3{\mathrm{N}}_4$ PIC-enabled OPM has detected the weak magnetic field with an optimal sensitivity of 0.53 pT $·$ ${\mathrm{Hz}}^{-1/2}$ at 70Hz. This work presents an effective approach for manipulation of alkali atoms using a chip and, crucially, introduces a chip-based pump solution for OPMs. This approach contributes to the integration of nanophotonics with atomic systems, paving the way for future advancements in quantum sensing.