Detection of a weak magnetic field via cavity-enhanced Faraday rotation

Abstract

We study the sensitive detection of a weak static magnetic field via Faraday rotation induced by an ensemble of spins in a bimodal degenerate microwave cavity. We determine the limit of the resolution for the sensitivity of the magnetometry achieved using either single-photon or multiphoton inputs. For the case of a microwave cavity containing an ensemble of Nitrogen-vacancy defects in diamond, we obtain a magnetometry sensitivity exceeding 0.5 nT/ √ Hz, utilizing a single photon probe field, while for a multiphoton input we achieve a sensitivity about 1fT/ √ Hz, using a coherent probe microwave field with power of Pin = 1 nW.

Rabi resonance in Cs atoms and its application to microwave magnetic field measurement

“…To date, atom-based measurements for static and radio-frequency fields have already had remarkable successes [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Recently, atom-based microwave (MW) measurement has also inspired great interest because of its potential ability to link the MW quantities with SI units.…”

High-sensitivity optical Faraday magnetometry with intracavity electromagnetically induced transparency

“…As a result, the phase shifts φ + (solid curve) and φ − (dashed curve) vary rapidly, leading to the enhancement of the Faraday rotation angle φ = (φ − − φ + )/2. This is the so called cavity-enhanced Faraday rotation [7]. The Faraday rotation angle φ versus probe detuning ∆ p is illustrated in Fig.…”

“…in Ref. [7], the physical mechanism behinds our Faraday magnetometry is intracavity EIT, not the resonance absorption. The transparency peak can therefore be controlled by the driving field and the adjustable number of atoms confined in the cavity.…”

“…The resonator response is consequently drastically modified, resulting in substantial narrowing of spectral features [25][26][27][28]. The cavity-enhanced Faraday rotation in NV centers in diamond can push the sensitivity of microwave magnetometer into aT/ √ Hz [7]. Furthermore, owing to the established technology for microcavity fabrication, cavities may be an attractive choice for miniaturized systems.…”

“…A particularly important application is magnetic resonance imaging. A variety of techniques including a superconducting quantum interference device (SQUID) [4], cavity optomechanical [5], negatively charged nitrogen-vacancy (NV) centers in diamond [6,7], and Bose-Einstein condensate (BEC) [8,9] have been suggested for extremely high sensitive optical magnetometry. There are two ways for sensing of magnetic fields.…”