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 1mm3 can achieve shot-noise limited d.c.~sensitivity of 1.86 fT/Hz and a.c.~sensitivity of 3.97fT/Hz.
@article{arxiv.1410.6239,
title = {Laser threshold magnetometry},
author = {Jan Jeske and Jared H. Cole and Andrew D. Greentree},
journal= {arXiv preprint arXiv:1410.6239},
year = {2016}
}