Uniform microwave field formation for control of ensembles of negatively charged nitrogen vacancy in diamond

TL;DR

This study compares and optimizes various microwave field-forming systems to enhance magnetic field uniformity for controlling NV center ensembles in diamond, crucial for sensitive magnetometry.

Contribution

The paper provides a detailed numerical comparison of five magnetic field systems and experimentally demonstrates improved homogeneity with a barrel-shaped coil.

Findings

Barrel-shaped coil shows significantly improved field homogeneity.

Numerical optimization enhances design parameters for uniform microwave fields.

Experimental Rabi oscillations confirm the improved uniformity.

Abstract

The homogeneity of the microwave magnetic field is essential in controlling a large volume of ensemble spins, for example, in the case of sensitive magnetometry with nitrogen-vacancy (NV) centers in diamond. This is particularly important for pulsed measurement, where the fidelity of control pulses plays a crucial role in its sensitivity. So far, several magnetic field-forming systems have been proposed, but no detailed comparison has been made. Here, we numerically study the homogeneity of five different systems, including a planar antenna, a dielectric resonator, a cylindrical inductor, a barrel-shaped coil, and a nested barrel-shaped coil. The results of the simulation allowed us to optimize the design parameters of the barrel-shaped field-forming system, which led to significantly improved magnetic field uniformity. To measure this effect, we experimentally compared the homogeneity of a field-forming system having a barrel shape with that of a planar field-forming system by measuring Rabi oscillations of an ensemble of NV centers with them. Significant improvements in inhomogeneity were confirmed in the barrel-shaped coil.