Design of tightly linked dual ring antenna and imaging of magnetic field distribution using a diamond fiber probe

A tightly linked dual ring antenna is designed, and it is specifically tailored for uniformly coupling the microwave magnetic field to the nitrogen-vacancy (NV) center. The designed antenna operates at a center frequency of about 2.87 GHz, with a bandwidth of around 200 MHz, allowing it to address multiple resonance peaks in the optically detected magnetic resonance (ODMR) spectrum in an external magnetic field. Moreover, the antenna generates a fairly uniform magnetic field in a range with a radius of 0.75 mm. High resolution imaging of the magnetic field distribution on the surface of the antenna is conducted by using a fiber diamond probe. We also investigate the effect of magnetic field uniformity on the linewidth of ODMR, so as to provide insights into reducing the inhomogeneous broadening of ODMR.