Optical Sensing of Broadband RF Magnetic Field Using a Micrometer-Sized Diamond

High-resolution field imaging with minimized invasiveness is of growing interest with the development of radio frequency (RF) integrated circuits and planar antenna characterization. In this paper, we propose an optical broadband sensor with static offset magnetic field using a diamond crystal that contains an ensemble of nitrogen-vacancy (NV) centers. The spatial resolution of micrometer scale is demonstrated by using a diamond crystal of this size. This technique is based on the modulation of fluorescence emitting by NV center under green laser excitation, by an off-axis magnetic field at radio frequencies. We demonstrate experimentally the detection of an RF magnetic field, with minimum measurable amplitude on the order of 0.1 Gauss, which is limited by the noise floor of the avalanche photodetector. The sensitivity can be further improved by noise suppression in optics. The bandwidth of the sensor is measured to be 15 MHz.