Designing Microwave Antennas for NV-Centre Magnetometry

Abstract

Nitrogen-vacancy centres in diamond are one of the most promising platforms for a wide range of applications due to their quantum sensing abilities, functionality at room temperature, and simple optical signal readout and manipulation via the use of microwave/RF radiation. Applying microwave radiation is not a very basic task, depending on the application that one wants. However, in a large area within an ensemble of NV centres in a crystal or even multiple crystals, that ensemble must be addressed along with a homogeneous microwave intensity, so a more specialised microwave antenna is needed. For magnetic field sensing in NV-ensemble diamond, a wider bandwidth antenna transmission is better for sensing. For targeting this goal, a complete procedure for developing PCB-based microstrip antennas and some other very efficient PCB-based antennas for NV centres applications is described in this work. For driving all NV centres that point in a given direction with the same intensity, we need uniform intensity over this area, which is not a very simple task to fabricate such an antenna. At a given input power, there is always a very significant chance of compromise between uniformness of the intensity and high intensity. In this procedure of fabricating these antennas, either using ferric-chloride or PCB milling in order to achieve the resolution for ODMR signal acquisition, fabrication and testing using a vector network analyser. The fabricated antennas reached a maximum transmission of 60% of the input power around the desired frequency (2.87 GHz), a more than 400 MHz bandwidth and are well capable of resolving electronic spin resonance with a very good contrast.