Spectral and Temporal Characteristics of Narrowband Superluminescence of NV– and C Centers in High-Pressure High-Temperature Diamond

We report a study of narrowband superluminescence of a single-sector {111} high-pressure high-temperature (HPHT) diamond plate with NV– and C centers at a total nitrogen and NV– center concentrations of ~60 ppm and 11 ppm, respectively. The sample is optically pumped with pulsed laser radiation (λ = 532 nm) focused by a cylindrical lens (f = 60 mm). It is found that, in the region of the pump beam waist, the superluminescence spectra exhibit a pronounced fine structure, while the radiation pulse has a spike shape with an exponential decrease in pulse intensity over time. With additional pumping with continuous radiation at λ = 403 nm, an increase in the superluminescence intensity is recorded, and the number of intense peaks in the radiation pulse also increases. As the volume of the sample with a population inversion gradually increases by moving it away from the pump beam waist, the superluminescence intensity increases steadily, accompanied by spectrum smoothing, reaching a maximum at approximately a twofold increase in the pump volume. It is found that, with a smooth narrowband superluminescence spectrum, a short single pulse is generated as the narrowband superluminescence intensity approaches saturation.