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arXiv · 1103.1192

Chopped nonlinear magneto-optic rotation: a technique for precision measurements

Harish Ravishankar·Sapam Ranjita Chanu·Vasant Natarajan
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Abstract

We have developed a technique for precise measurement of small magnetic fields using nonlinear magneto-optic rotation (NMOR). The technique relies on the resonant laser beam being chopped. During the on time, the atoms are optically pumped into an aligned ground state ($Δm=2$ coherence). During the off time, they freely precess around the magnetic field at the Larmor frequency. If the on-off modulation frequency matches (twice) the Larmor precession frequency, the rotation is resonantly enhanced in every cycle, thereby making the process like a repeated Ramsey measurement of the Larmor frequency. We study chopped-NMOR in a paraffin-coated Cs vapor cell. The out-of-phase demodulated rotation shows a Lorentzian peak of linewidth 85 $μ$G, corresponding to a sensitivity of 0.15 nG/$\sqrt{\rm Hz}$. We discuss the potential of this technique for the measurement of an atomic electric-dipole moment.

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Harish Ravishankar, Sapam Ranjita Chanu, Vasant Natarajan. 2011-03-07. Chopped nonlinear magneto-optic rotation: a technique for precision measurements. https://doi.org/10.1209/0295-5075%2F94%2F53002

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