Prospects for Two-Photon Optical Magnetometry

Dmitry Budker, Michael V. Romalis

Xuting Yang, Meryem Benelajla, S. Carpenter +1 more

Atomic magnetometry is one of the most sensitive field-measurement techniques for biological, geo-surveying, and navigational applications. An essential process in atomic magnetometry is measurement of optical polarization rotation of a near-resonant beam due to its interaction with atomic spins under an external magnetic field. In this work, we present the design and analysis of a silicon-metasurface-based polarization beam splitter that have been tailored for operation in a rubidium magnetometer. The metasurface polarization beam splitter operates at a wavelength of 795 nm and has a transmission efficiency > 83% and a polarization extinction ratio > 20 dB. We show that these performance specifications are compatible with magnetometer operation in miniaturized vapor cells with sub-picotesla-level sensitivity and discuss the prospect of realizing compact, high-sensitivity atomic magnetometers with nanophotonic component integration.

Roger C. Brown, Saijun Wu, Thomas Plisson +2 more

Skyler Degenkolb

Optical magnetometry plays a critical role in low-energy precision measurements and numerous other applications. In particular, permanent electric dipole moment (EDM) searches impose strict requirements on magnetic field sensitivity of the underlying atomic or molecular species. Other magnetometer properties -- such as chemical reactivity, dielectric strength, and interaction cross-sections with other species -- also impose limitations on experimental conditions. Here, we explore a novel approach to optical magnetometry, using multiphoton transitions of diamagnetic atoms to detect Larmor precession of polarized nuclei. Resonant probes are possible at moderate ultraviolet wavelengths, and hyperfine structure couples spin precession to fluorescence transitions with negligible backgrounds; paramagnetic rotation due to intensity-dependent dispersion may also be detectable. Nuclear spins and nonlinear optical excitation introduce new degrees of freedom, and evade limitations arising from rapid electronic decoherence. This dissertation reports progress towards two-photon optical magnetometry using ytterbium, rubidium, and xenon. We characterize the influence of probe polarization and magnetic fields on fluorescence spectra, for one- and two-photon continuous-wave (cw) excitation of ytterbium. Resolved hyperfine and isotope structure allow us to use spin-zero isotopes for diagnostics and normalization, and we develop analysis for overlapping two-photon resonances. We also report measurements of two-photon excitation in ytterbium and rubidium using picosecond laser pulses, and in xenon using a cw laser. Although hyperfine structure is unresolved, the rubidium measurements are sensitive to probe field polarization. Fluorescence spectra from two-photon excitation of ytterbium with femtosecond pulses show modulation when the repetition rate changes. Although techniques for polarizing noble gas nuclei are mature, existing cell designs are incompatible with two-photon magnetometry. We describe development of silicate-assisted hydroxide-catalysis bonding for both aluminosilicate EDM cells with silicon electrodes, and sapphire-windowed cells that transmit ultraviolet excitation light. Progress in measuring the 129Xe nuclear EDM is discussed. Absolute referencing of the picosecond laser to potassium transitions is proposed for two-photon spectroscopy of ytterbium and xenon, and a compatible frequency-tripling method is outlined to produce excitation light for xenon. Novel possibilities including spatial resolution and multiphoton optical pumping of nuclear spins are considered.

Dmitry Budker

Wenhao Li, Xiang Peng, Dmitry Budker +4 more

Dynamic hybrid optical pumping effects with a radio-frequency field-driven nonlinear magneto-optical rotation scheme are studied in a dual-species paraffin coated vapor cell. By pumping K atoms and probing Rb87 atoms, we achieve an intrinsic magnetic resonance linewidth of 3 Hz, and the observed resonance is immune to power broadening and light-shift effects. Such an operation scheme shows favorable prospects for atomic magnetometry applications.