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 of87 Rb $^{87}{\rm Rb}$ atoms using a fiber‐coupled silicon nitride (Si 3 N 4 ${\rm Si}_3{\rm N}_4$ ) 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%. TheSi 3 N 4 ${\rm Si}_3{\rm N}_4$ PIC‐enabled OPM has detected the weak magnetic field with an optimal sensitivity of 0.53 pT · $\cdot$Hz − 1 / 2 ${\rm Hz}^{-1/2}$ 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.