Fiber-Coupled Diamond Magnetometry with an Unshielded Sensitivity of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mn>30</mml:mn><mml:mspace width="0.1em"/><mml:mi>pT</mml:mi><mml:mo>/</mml:mo><mml:msqrt><mml:mi>Hz</mml:mi></mml:msqrt></mml:math>
Suzanne Graham, Anisur Rahman, L. Munn, R. L. Patel, A.J. Newman, Colin Stephen, Gerard Colston, Alexander P. Nikitin, Andrew M. Edmonds, Daniel J. Twitchen, Matthew Markham, Gavin W. Morley
Abstract
Ensembles of nitrogen-vacancy centers (NVCs) in diamond can be employed for sensitive magnetometry. In this work, we present a fiber-coupled NVC magnetometer with an unshielded sensitivity of $(30\ifmmode\pm\else\textpm\fi{}10)\phantom{\rule{0.2em}{0ex}}\mathrm{pT}/\sqrt{\mathrm{Hz}}$ in a (10--500)-Hz frequency range. This sensitivity is enabled by a relatively high green-to-red photon conversion efficiency, the use of a [100] bias-field alignment, microwave and lock-in amplifier (LIA) parameter optimization, as well as a balanced hyperfine-excitation scheme. Furthermore, a silicon carbide ($\mathrm{SiC}$) heat spreader is used for microwave delivery, alongside low-strain 1-${\mathrm{mm}}^{3}{\phantom{\rule{0.2em}{0ex}}}^{12}$$\mathrm{C}$ diamonds, one of which is placed in a second magnetically insensitive fluorescence-collecting sensor head for common-mode noise cancellation. The magnetometer is capable of detecting signals from sources such as a vacuum pump up to 2 m away, with some orientation dependence but no complete dead zones, demonstrating its potential for use in remote-sensing applications.