Continuous-Wave Magnetic Field Sensing with Nitrogen-Vacancy Centers in Diamond

Sepehr Ahmadi

Research output: Book/ReportPh.D. thesisResearch

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The nitrogen-vacancy center, a point defect in diamond, is a promising quantum sensor for magnetic field sensing with high sensitivity and high spatial resolution under ambient conditions. Such a magnetometer has potential applications in various fields, including neuroscience, microelectronics, and
nanoscale magnetic resonance microscopy.
This thesis presents cavity-enhanced magnetic field sensing using ensembles of nitrogen-vacancy centers in diamond. We apply a phase-sensitive detection method in our experiments and discuss our efforts regarding exploring the ideal modulation conditions. We demonstrate a ∼ 400 pT/√Hz magnetic noise density spanning a bandwidth up to 125 Hz, by measuring the changes in the fluorescence level. Using a five-level model for nitrogen-vacancy centers, a physical model is developed that shows excellent agreement with the measured optically detected magnetic resonance spectra.
Furthermore, we introduce an alternative technique for measuring the electron spin-states of nitrogen-vacancy centers based on recording the absorption of the pump light. This method is employed for magnetic field sensing, and a magnetic noise floor of ∼ 100 nT/√Hz is measured spanning a bandwidth up to 125 Hz. We modified the five-level model to describe the absorption detected magnetic resonance of a diamond placed inside an optical cavity. The model agrees very well with experiments.
Original languageEnglish
Place of PublicationLyngby, Denmark
PublisherTechnical University of Denmark
Number of pages100
Publication statusPublished - 2018


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