Abstract

MASERs are devices that exploit stimulated emission to amplify electromagnetic waves at microwave frequencies. Their principal advantage over conventional (semiconductor-based) electronic amplifiers is lower noise. An optically-pumped, solid-state pentacence maser operating at room temperature in pulsed mode was demonstrated [1]. This was followed by the recent demonstration of a continuous maser at room temperature using colour centres (NV) in diamond [2] paving the way for a new class of masers that could find new applications in medicine, security and sensing, quantum computing/information processing. Here we report the room-temperature and low-temperature absorption spectroscopy (UV-VIS-NIR), and electron paramagnetic resonance spectroscopy (EPR) conducted over a range of chemical vapour deposition (CVD) grown diamond samples. Fig.1 shows the results for the room temperature absorption and fluorescence studies. We also compared the room-temperature spectra with the experimental results conducted at 80 K. Finally, we used these data to calculate the density of NV⁻ in these samples that is responsible for the maser action. The number of NV⁻ defect centres is crucial since the total available number of NVs that are useful for maser are limited by the hyperfine coupling with nitrogen. From our previous studies, an NV⁻ concentration that lies between 0.2 to 2 ppm will offer the best solution in terms of pumping efficiency and uniform pumping rate for maser.

© 2019 IEEE