Ph.D Thesis


Ph.D StudentSherman Alexander
SubjectTowards the Implementation of a Versatile Diamond-Based Room
Temperature MASER
DepartmentDepartment of Chemistry
Supervisor PROF. Aharon Blank
Full Thesis textFull thesis text - English Version


Abstract

Quantum technology (QT) is an emerging field of science that makes use of unique quantum mechanical properties such as discreteness of energy levels, superposition of states and entanglement, for practical applications such as quantum computing, quantum sensing, quantum clocks, and quantum communication. Prime examples of quantum entities useful for QT are the electron spins of atom-like crystal defects. A well-studied and very promising crystal point defect is the negatively charged nitrogen-vacancy (NV-) center in diamond, having discrete energy levels and populations that can be manipulated via a combination of a static magnetic field (Zeeman splitting) and electromagnetic radiation in the microwave and optical domains. This research is focused on one possible QT application of the NV- center: a MASER (Microwave Amplification by Stimulated Emission of Radiation). The NV--based MASER can be either operated as a microwave source (quantum clock) or as a quantum amplifier - at room temperature. Such MASER device could have superior properties of low phase noise (when operating as a microwave source) and low noise temperature (when operating as an amplifier). In this work, the proposed MASER is based on an ensemble of NV- centers in a bulk single-crystal diamond situated inside a high quality-factor microwave resonator. A 520 [nm] light source combined with a static magnetic field is used in order to establish sufficient population inversion among the Zeeman splitted energy levels and using the unique optically-induced spin polarization properties of the NV- center. With sufficient population inversion, the gain for incoming microwave photons is expected to overcome the resonator losses and initiate the masing process. We have designed, constructed and tested several novel prototypes of such MASER devices, operating at 10 and 35 [GHz]. The proposed novel resonator can house the active gain material, enable efficient light illumination, and have high filling factor of η=0.8 along with sufficiently high quality-factor. We followed with the characterization, production, and analysis of the properties of the single crystal diamond material needed for stable and efficient MASER operation. To support these efforts we also developed several infrastructure methodologies, such as special electron spin resonance (ESR) probeheads for light-induced continuous wave and pulsed ESR. The attained materials are shown to be capable supporting the desired MASER specifications, even with the discovery of an unexpected dielectric losses in the diamonds (tan(δ) ~ 0.015) , by the utilization a low-loss dielectric slab inside the proposed cavity which acts to mitigate the dielectric losses due to the diamonds. Moreover, several numerical models and experimental methods were developed to enable detailed analysis of both the expected and currently attained performance of the MASER, as a function of the diamond material properties, cavity characteristics, and light excitation magnitude. While we have yet to demonstrate a truly operational room temperature MASER system, our models indicate that we are not far from realizing the masing threshold, and expect to bridge the remaining gap with additional improvements in the diamond material, cavity structure and light excitation method. We can also estimate the noise performance of the MASER, showing that it can possess a noise temperature which is far lower than its ambient temperature.