Quantum imaging: optically detected magnetic resonance of nanodiamond

Optically Detected Magnetic Resonance (ODMR) imaging of fluorescent nanodiamond (FND) allows thermometry and magnetometry at a cellular level. It takes advantage of FND’s biocompatibility and small size (between 5 and 100nm). Nitrogenvacancy (NV) defects in the FND are optically excited at 532nm while applying a microwave field that is scanned around the resonant frequency of the triplet ground state of the NV (approximately 2.87GHz). There are two decay paths that offer differing emission intensities and that are coupled to the (microwave-controlled) spin state of the NV centre: By monitoring the change in fluorescence as a function of applied microwave frequency (the ODMR curve), the spin state of the NV centre can be inferred. Furthermore, this transition is both thermally and magnetically dependent; a magnetic shift sees a splitting of the detected response through the Zeeman effect and a thermal change sees a frequency shift that applies equally to all components of the curve. There have been many implementations of ODMR-compatible imaging systems, however they typically use high-cost components in complex setups. We present here methods for ODMR using a low-cost sCMOS camera, in both wide-field epifluorescence and wide-field total internal reflection fluorescence (TIRF) microscopy. We will discuss the design of the microscope, the experimental scope of the system, a comparison to other experimental techniques already available and the benefits of a lower-cost system including its feasibility for further experimental applications.