Adam M. Wojciechowski

Magnetometry based on nonlinear magneto-optical rotation with amplitude-modulated light

Nonlinear magneto-optical rotation (NMOR), an all-optical technique now finding its use in sensitive magnetometry, is light-intensity-dependent rotation of the polarization plane of linearly polarized light upon its propagation through a medium placed in a magnetic field. NMOR technique enables measurements of magnetic field from 0 to 50 muT with the expected sensitivity of 10-14 T Hz-1/2.

Nonlinear magneto-optical rotation and Zeeman and hyperfine relaxation of potassium atoms in a paraffin-coated cell

Nonlinear magneto-optical Faraday rotation (NMOR) on the potassium D1 and D2 lines was used to study Zeeman relaxation rates in an antirelaxation paraffin-coated 3-cm-diameter potassium vapor cell. Intrinsic Zeeman relaxation rates of {gamma}{sup NMOR}/2{pi}=2.0(6) Hz were observed. The relatively small hyperfine intervals in potassium lead to significant differences in NMOR in potassium compared to rubidium and cesium. Using laser optical pumping, widths and frequency shifts were also determined for transitions between ground-state hyperfine sublevels of {sup 39}K atoms contained in the same paraffin-coated cell. The intrinsic hyperfine relaxation rate of {gamma}{sub expt}{sup hf}/2{pi}=10.6(7) Hz and a shift of -9.1(2) Hz were observed. These results show that adiabatic relaxation gives only a small contribution to the overall hyperfine relaxation in the case of potassium, and the relaxation is dominated by other mechanisms similar to those observed in previous studies with rubidium.

All-optical atomic magnetometers based on nonlinear magneto-optical rotation with amplitude modulated light

We demonstrate a magnetometric technique based on nonlinear magneto-optical rotation using amplitude modulated light. The magnetometers can be operated in either open-loop (typical nonlinear magneto-optical rotation with amplitude-modulated light) or closed-loop (self-oscillating) modes. The latter mode is particularly well suited for conditions where the magnetic field is changing by large amounts over a relatively short timescale.

Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles

Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≳ 1/4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate a model for calculating lock-in spectra which shows excellent agreement with our experiments, and which shows that an optimum slope is achieved when the linewidth/separation ratio is ≲ 1/4 and the modulation depth is less then the resonance linewidth, irrespective of the modulation function used.

Coherent population oscillations with nitrogen-vacancy color centers in diamond

We present results of our research on two-field (two-frequency) microwave spectroscopy in nitrogen-vacancy (

Magneto-optical effects and rf magnetic field detection in cold rubidium atoms

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Contributed Review: Camera-limits for wide-field magnetic resonance imaging with a nitrogen-vacancy spin sensor

) color centers in a diamond. Both fields are tuned to transitions between the spin sublevels of the

Optimal geometry for efficient loading of an optical dipole trap

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Atomic-state diagnostics and optimization in cold-atom experiments

ensemble in the

Creation and measurement of coherent superposition states in multilevel atoms

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