High-Speed NV Ensemble Magnetic Field Imaging via Laser Raster Scanning

TL;DR

This paper introduces a high-speed magnetic field imaging method using NV centers in diamond, employing laser raster scanning in a novel quasi-continuous-wave regime to achieve high spatial and temporal resolution with simplified control.

Contribution

The authors develop a new imaging technique that combines laser raster scanning with a quasi-continuous-wave ODMR regime, enhancing sensitivity and simplifying experimental setup for dynamic magnetic field detection.

Findings

Achieves sub-millisecond temporal resolution in magnetic field imaging.

Demonstrates nT/√Hz sensitivity per pixel.

Operates effectively without precise microwave pulse control.

Abstract

We present a technique that uses an ensemble of nitrogen-vacancy (NV) centers in diamond to image magnetic fields with high spatio-temporal resolution and sensitivity. A focused laser beam is raster-scanned using an acousto-optic deflector (AOD) and NV center fluorescence is read out with a single photodetector, enabling low-noise detection with high dynamic range. The method operates in a previously unexplored regime, quasi-continuous-wave optically detected magnetic resonance (qCW-ODMR). In this regime, NV centers experience short optical pump pulses for spin readout and repolarization -- analogous to pulsed ODMR -- while the microwave field continuously drives the spin transitions. We systematically characterize this regime and show that the spin response is governed by a tunable interplay between coherent evolution and relaxation, determined by the temporal spacing between pump laser pulses. Notably, the technique does not require precise microwave pulse control, thus simplifying experimental implementation. To demonstrate its capabilities, we image time-varying magnetic fields from a microwire with sub-millisecond temporal resolution. This approach enables flexible spatial sampling and, with our diamond, achieves $\text{nT}/\sqrt{\text{Hz}}$-level per-pixel sensitivity, making it well suited for detecting weak, dynamic magnetic fields in biological and other complex systems.