Peculiarities of nitrogen-vacancy centers’ superluminescence in diamond under optical pumping at 532 nm

In the context of the NV − diamond laser creation (Savvin and Dormidonov in Nat. Commun. 12:7118, 2021), an urgent task is to determine the characteristics of diamonds that can affect laser generation. This work is aimed at investigating the mechanisms of the creation of superluminescence in diamond under the action of optical pumping by the second harmonic of the Nd:YAG laser (λ = 532 nm). It was found that when the HPHT diamond is irradiated by 532 nm radiation with an intensity above ~ 2.0 MW/cm 2 , a nonlinear intensity increasing in the spectral region 700–750 nm is manifested against the background of the spontaneous photoluminescence spectrum, which, with a further pumping intensity increase turns into a pronounced peak of superluminescence with a maximum of about 718 nm. An increase in the pumping intensity from 2.7 to 46 MW/cm 2 widened this peak at half-maximum from 13 to 19 nm. At high levels of pumping intensity, nonlinear pumping radiation absorption and accumulation of NV centers in the excited state were detected. The position of the photoluminescence band was calculated depending on different values of the population inversion density of the color centers, taking into account the diamond's own absorption spectrum. The calculation results are close to the experimental data.