Microscale Fiber-Integrated Vector Magnetometer with On-Tip Field Biasing using NV Ensembles in Diamond Microcystals

TL;DR

This paper introduces a compact fiber-integrated vector magnetometer using NV centers in diamond, employing a microscale coil at the fiber tip for localized biasing and control, enabling full solid-angle magnetic field measurement with high sensitivity.

Contribution

It presents a novel fiber-tip coil design for vector magnetometry with NV centers, eliminating bulky external biasing equipment and enabling miniaturized, high-resolution magnetic sensing.

Findings

Achieved shot-noise limited sensitivity of 19.4 nT/Hz^{1/2}.

Demonstrated full solid-angle vector magnetic field measurement.

Realized microscale spatial resolution below 1 mm^2.

Abstract

In quantum sensing of magnetic fields, ensembles of nitrogen-vacancy centers in diamond offer high sensitivity, high bandwidth and outstanding spatial resolution while operating in harsh environments. Moreover, the orientation of defect centers along four crystal axes forms an intrinsic coordinate system, enabling vector magnetometry within a single diamond crystal. While most vector magnetometers rely on a known bias magnetic field for full recovery of three-dimensional field information, employing external 3D Helmholtz coils or permanent magnets results in bulky, laboratory-bound setups, impeding miniaturization of the device. Here, a novel approach is presented that utilizes a fiber-integrated microscale coil at the fiber tip to generate a localized uniaxial magnetic field. The same fiber-tip coil is used in parallel for spin control by combining DC and microwave signals in a bias tee. To implement vector magnetometry using a uniaxial bias field, we preselect the orientation of the diamond crystal and then fully characterize it by rotating a static magnetic field in three planes of rotation. We demonstrate the measurement of vector magnetic fields in the full solid angle with a shot-noise limited sensitivity of $19.4\:\textrm{nT/Hz}^{1/2}$ and microscale spatial resolution while achieving a cross section of the fiber sensor head below $1\:\textrm{mm}^2.$