Avoiding power broadening in optically detected magnetic resonance of single NV defects for enhanced DC-magnetic field sensitivity

TL;DR

This paper demonstrates a pulsed-ESR technique that eliminates power broadening in NV center magnetic resonance, significantly enhancing DC magnetic field sensitivity to levels comparable with Ramsey sequences.

Contribution

The authors introduce a pulsed-ESR scheme that removes power broadening effects, improving NV-based magnetic sensing sensitivity by an order of magnitude.

Findings

Optimized sensitivity of ~2 μT/√Hz with continuous ESR.

Enhanced sensitivity by tenfold using pulsed-ESR.

Sensitivity comparable to Ramsey sequences for DC magnetic fields.

Abstract

We report a systematic study of the magnetic field sensitivity of a magnetic sensor based on a single Nitrogen-Vacancy (NV) defect in diamond, by using continuous optically detected electron spin resonance (ESR) spectroscopy. We first investigate the behavior of the ESR contrast and linewidth as a function of the microwave and optical pumping power. The experimental results are in good agreement with a simplified model of the NV defect spin dynamics, yielding to an optimized sensitivity around 2 \mu T/\sqrt{\rm Hz}. We then demonstrate an enhancement of the magnetic sensitivity by one order of magnitude by using a simple pulsed-ESR scheme. This technique is based on repetitive excitation of the NV defect with a resonant microwave \pi-pulse followed by an optimized read-out laser pulse, allowing to fully eliminate power broadening of the ESR linewidth. The achieved sensitivity is similar to the one obtained by using Ramsey-type sequences, which is the optimal magnetic field sensitivity for the detection of DC magnetic fields.