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 (QC), quantum sensing (QS), quantum clocks, and quantum communication with single photons (QCom). 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 nitrogen–vacancy (NV) center in diamond, which exhibits properties of a 7-level atomlike quantum system having energy levels and populations that can be manipulated via a combination of Zeeman splitting and electromagnetic radiation in the MW and optical domains. This research is focused on one possible QT application of the NV center in diamond: a quantum clock/amplifier based on MASER (microwave amplifier by stimulated emission of radiation). The 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). The proposed maser in this work 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 splitted energy levels, due to the Zeeman effect and unique optically-induced spin polarization properties of the NV center. When the population inversion in the NVs is large enough, the gain for incoming microwave photons is expected to overcome the resonator losses and initiate the masing process. During this research we designed, constructed and tested several prototypes of the maser devices, operating at ∼ 10 and ∼ 35 [GHz]. This included the production and analysis of the properties of the diamond single crystal material needed for its operation, as well as design and production of unique microwave resonators that achieve high filling factor for the diamond material and enable efficient light excitation. To support these efforts we also developed several infrastructure tools. For example, the analysis of diamond material properties required construction of special electron spin resonance (ESR) probeheads for light-induced continuous wave (CW) and pulsed ESR. Moreover, several numerical models were developed to enable detailed analysis of the expected performance of the MASER, as a function of the diamond material properties, resonator, and light excitation magnitude. While we have yet to demonstrate a truly operational room temperature maser system, we laid out the required path for its construction and also present the details of the required test procedure.