Laser threshold magnetometry

TL;DR

This paper introduces laser threshold magnetometry (LTM), a novel NV$^-$-center-based magnetometer that uses laser threshold behavior for highly sensitive magnetic field detection at room temperature.

Contribution

The paper presents a new magnetometry approach using NV$^-$ centers in diamond that employs laser threshold behavior for enhanced sensitivity, differing from traditional fluorescence-based methods.

Findings

Predicts 1.86 fT/√Hz sensitivity for DC magnetic fields.

Achieves 3.97 fT/√Hz sensitivity for AC magnetic fields.

Operates effectively at room temperature with fiber coupling.

Abstract

We propose a new type of sensor, which uses diamond containing the optically active nitrogen-vacancy (NV$^-$) centres as a laser medium. The magnetometer can be operated at room-temperature and generates light that can be readily fibre coupled, thereby permitting use in industrial applications and remote sensing. By combining laser pumping with a radio-frequency Rabi-drive field, an external magnetic field changes the fluorescence of the NV$^-$ centres. We use this change in fluorescence level to push the laser above threshold, turning it on with an intensity controlled by the external magnetic field, which provides a coherent amplification of the readout signal with very high contrast. This mechanism is qualitatively different from conventional NV$^-$--based magnetometers which use fluorescence measurements, based on incoherent photon emission. We term our approach laser threshold magnetometry (LTM). We predict that an NV$^-$--based laser threshold magnetometer with a volume of 1mm$^3$ can achieve shot-noise limited d.c.~sensitivity of 1.86 fT$/\sqrt{\rm{Hz}}$ and a.c.~sensitivity of 3.97fT$/\sqrt{\rm{Hz}}$.