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High-resolution, Ultra-sensitive Magnetic Imaging Using an Ensemble of Nitrogen-Vacancy (NV) Centers in Diamond


OBJECTIVE: Develop compact magnetic field imagers with nT/Hz^1/2 field sensitivity and sub-micron spatial resolution using an optically-addressed ensemble of NV centers in diamond. DESCRIPTION: Highly sensitive magnetic field imaging systems are important tools in both military and civil sectors, finding applications ranging from the detection of landmines and submarines to the high-resolution imaging of sub-cellular phenomena. State-of-the-art high-resolution magnetometers, Superconducting Quantum Interference Devices (SQuIDs), are frequently found in medical devices for magnetoencephalography (MEG) and magnetic resonance imaging (MRI). They can operate at the nT/Hz^1/2 level but are limited to micron resolution, require cryogenic environments, and consume high power. An attractive means of boosting the sensitivity and resolution of modern magnetometers in a room temperature, low power and rugged device, is to employ optically-addressed ensembles of NV centers in diamond. As well as supplanting SQUIDS in medical applications, such magnetometers, with sub-micron spatial resolution, could be used in the non-destructive imaging of integrated circuits for the presence of malicious circuits. NV centers are atom-like defects in diamond that are highly sensitive to magnetic fields despite being embedded in the solid state. In fact, operation at the pT/Hz^1/2 level has been demonstrated and it is expected that nm-scale resolution can be achieved [1-4]. This approach is particularly exciting for biological and neuroscience applications because it works under ambient conditions (room temperature and pressure) without significantly affecting the operation. Furthermore, ensemble NV magnetometry offers a large field-of-view, a robust, solid state system and low noise optical preparation and detection. Because sensitivity scales as the square root of the number of NV centers [5], ensembles are essential to achieving high-sensitivity over a broad area. While impressive results have been obtained in the laboratory, significant development is necessary to construct a robust packaged imaging system with high-NV density and sufficiently narrow inhomogeneous broadening, reduced background noise and efficient collection efficiency. Methods of achieving the critical properties of a magnetic imager could include, but are not limited to, an improved collection efficiency with solid-immersion lenses [6], side collection schemes or anti-reflection coatings; reduced background noise with IR absorption spectroscopy [2] in a low finesse resonant cavity or obtaining high resolution with STED spectroscopy [7]. PHASE I: Design a robust packaged magnetic field imaging system with an ensemble of NV centers in diamond. Such a system should include high-grade diamond with NV ensembles with long coherence times, a novel imaging system with high-resolution, and optimized NV collection efficiency over a broad area. The chosen work must be compatible with an imaging system that has 1-10 nT/Hz^1/2 ac sensitivity and a 10-100 nm spatial resolution. Exhibit the feasibility of the approach through a laboratory demonstration. Phase I deliverables will include a design review including expected device performance and a report presenting the plans for Phase II. Experimental data demonstrating feasibility of the proposed device is favorable. PHASE II: Fabricate and test a prototype device demonstrating the device performance outlined in Phase I. The Transition Readiness Level to be reached is 5: Component and/or bread-board validation in relevant environment. PHASE III:Compact magnetic field imagers at the submicron level could have applications in the non-destructive imaging of integrated circuits for the presence of malicious circuits and neuronal and brain imaging. Operation at room temperature may lead to numerous applications in the imaging of living tissue such as imaging the structure and composition of proteins and molecules possibly in real time, informing the development of pharmaceuticals. Innovations in Phases I and II will enable such devices to transition out of the laboratory and into fieldable devices.
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