One of the most promising candidates to use as compact high sensitivity magnetometers is the Nitrogen-Vacancy (NV) center, however traditional implementations of this technology are plagued by low collection efficiencies or poor signal contrasts of the Optically Detected Magnetic Resonance (ODMR). Laser Threshold Magnetometry (LTM) offers a path towards both efficient signal collection and high signal contrasts by taking advantage of near threshold laser dynamics. We demonstrate an infrared LTM using a Vertical External Cavity Surface Emitting Laser (VECSEL) with an intra cavity diamond plate doped with NV centers. The VECSEL was tuned to the spin dependent absorption line of the NV centers, which tied the VECSEL output power to the magnetic field sensed by the NV centers. Furthermore, the contrast and the projected sensitivity limit are shown to improve when operating close to the lasing threshold. We measure a sensitivity of 7.5 nT/√ Hz between 10-50 Hz with a contrast of 18.4% and a projected Photon Shot Noise Limited (PSNL) sensitivity of 26.6 pT/√ Hz close to threshold. We also observe a saturable absorption-like effect near threshold, which further enhances the signal contrast and projected PSNL near threshold. A rate equation model for the VECSEL threshold magnetometer is described and is fit to mimic the observed threshold dynamics.
The NV-Biosensor uses a fluorescent nitrogen-vacancy center nanodiamond and diamond magnetometry to detect biological targets with high sensitivity. It can be designed to sense nucleic acid or protein biomarkers that are indicative of physiologic conditions, such as viral infection, chem-bio exposure, stress levels, cardiac distress, and even cancer markers. Once fully developed, the NV-Biosensor can be used to continuously monitor Warfighters for their well-being while in the field. We describe our preliminary results to create an NV-Biosensor that can detect nucleic acid biomarkers of stress and include a description of our optical set-up, biochemical methods, bioconjugation strategies and preliminary results.
Point defects in semiconductors are useful as quantum sensors, quantum emitters, and qubits for quantum computation. We have used ab initio quantum chemistry (supercell) calculations to model the photoluminescence of a new vanadium-nitrogen defect in diamond. Using ion implantation, we have attempted to synthesize this defect, and I will present spectroscopic analysis of our sample. Nanoscale positioning of defects is desired to improve the reliable coupling of defect centers to quantum photonic devices. I will discuss the merits of several methods for achieving this: introduction of functionalized seed molecules during diamond synthesis, laser annealing, and ion implantation. I will also present a scalable opto-thermal-mechanical printing method for additively releasing nanoparticles from a donor substrate and transferring them to a target substrate, such as a photonic device. Such integration is a crucial step towards realizing commercially scalable quantum sensing devices.
Semiconductor quantum dots provide a platform for studying and exploiting individual electron spins as they
interact with a complex solid state environment. Colloidal nanocrystal quantum dots are of particular interest
for potential applications, because they can achieve sufficient confinement to operate at room temperature with
relatively robust electron spin coherence. The strong confinement in these nanostructures leads to significant
effects caused by mixing of valence subbands and variation in particle size and shape. These effects influence
the processes of carrier spin initialization and detection. We have performed ensemble time-resolved Faraday
rotation experiments as well as single-dot photoluminescence excitation measurements to study how the strong
quantum confinement affects the spin physics in these systems. Single dot PLE measurements reveal mechanisms
of transition broadening that are relevant at room temperature, including thermal broadening and spectral
diffusion due to mobile charges in the surrounding environment. We find that the mixing of valence subbands
in the confined hole states largely determines the efficiency of optical spin pumping and Faraday-rotation-based
spin detection. By studying these effects, we take a step towards controlling and exploiting spin coherence in
this flexible room temperature platform.
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