Quantum sensing is broadly defined as the use of quantum materials, quantum coherence, and/or quantum entanglement to measure physical quantities and/or to enhance the sensitivity of classical analytical measurements. Certain materials exhibit interesting quantum properties that have the potential to be utilized in quantum sensing applications. One such quantum property is electronic spin, which is utilized in this work. Here, we built a custom apparatus capable of conducting both optically detected magnetic resonance (ODMR) and spin relaxometry. The quantum material investigated was an ensemble of nitrogen vacancies (NV) in nanodiamonds. We have characterized the system and measured ODMR spectra at different applied DC magnetic fields and observed the expected splitting of the resonances due the Zeeman effect. We also have measured the spin relaxation times for two different powers of the applied AC magnetic field. The lower power dataset exhibited expected exponential temporal dependence of the relaxation of a modified spin state, whereas the higher power dataset exhibited stretched exponential dependence of the evolution of the modified spin state, indicating the presence of high-power phenomena that emerge that retard the relaxation of the spin state.
This paper introduces a fluorometer that is both economically viable and optimized for sensitivity. The sensor is designed to detect low concentrations of fluorophores in the visible spectrum range, utilizing a deep ultraviolet (DUV) 275-nm LED and a dichroic mirror to establish a co-axial optical path for excitation and emission. Unlike traditional general-purpose spectrometers, this sensor achieves a balance between the two through an appropriate aperture size and tailored optical design optimized for the spectral characteristics of fluorophores. The manuscript presents measurements of rare earth element (REE) samples containing terbium (Tb), europium (Eu), dysprosium (Dy), and samarium (Sm) in aqueous solutions at ppb-level concentrations. By optimizing the collection of fluorescence emission without sacrificing spectral information, this work demonstrates the feasibility of developing a low-cost, compact, and highly sensitive fluorescence sensor that is comparable to bench-top commercial spectrofluorometers at a fraction of the cost.
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