Enhancing room-temperature solid-state maser: approaches in multiphysics simulation, zero-field time-resolved epr spectroscopy, and quantum-cumulant modeling

Masers, the microwave analogues of lasers, have attracted significant attention following the discovery of gain materials that operate at room temperature and zero magnetic fields. However, no room-temperature maser design has yet demonstrated continuous operation with robust performance suitable for practical applications. This thesis presents three approaches to enhance room-temperature solid-state masers. A novel design for the maser cavity using piezoelectric materials is proposed. Correspondingly, a simulation tool based on weak forms and finite-element-method (FEM) software has been developed. This tool surpasses the limitations of the quasi-static approximation. It enables accurate prediction of the magnetic field strength generated by the piezoelectric cavity, which can directly interact with maser gain materials. Three test cases illustrate the accuracy and capability of this tool. Although this new design ultimately demonstrates limited magnetic energy conversion efficiency, the simulation tool offers broad applicability in designing antennas, resonators, and waveguides that utilize bulk or surface acoustic waves. Another approach is to find new maser gain materials. Zero-field time-resolved electron paramagnetic resonance (ZF-trEPR) spectroscopy provides a quick inspection of their potential performance, especially the spin-lattice relaxation and depopulation rates. The theoretical background and experimental procedures are introduced. The ZF-trEPR was conducted on various candidate materials, with relatively strong signals observed for 0.01% mol/mol 6,13-diazapentacene-doped para-terphenyl (DAP:PTP), 0.1% mol/mol 5,12-diazatetracene-doped 1,3,5-tri(1-naphthyl)benzene (DAT:1-TNB), 0.1% mol/mol 1,5,12-triazatetracene-doped 1,3,5-tri(1-naphthyl)benzene (TrAT1:1-TNB), and 0.1% mol/mol 2,5,12-triazatetracene-doped 1,3,5-tri(1-naphthyl)benzene (TrAT2:1-TNB). The results are presented and analyzed in detail. The quantum-cumulant method, implemented using the Julia programming language and the QuantumCumulant.jl package, is employed to simulate maser signals. This approach validates the masers' theoretical framework and predicts the masing performance of potential materials. It can provide a guide to on further research. A comprehensive guide is provided, accompanied by results from simulations of complex models that are not tractable through analytical methods.