Superluminescence at Nitrogen-Vacancy Centers in the Synthetic Diamond Pumped by Laser Radiation in the Range of 532−575 nm

Photoluminescence spectra of two synthetic diamond samples containing 1−10 ppm nitrogen-vacancy (NV) centers and 100−200 ppm substitutional nitrogen were studied under optical pumping at 532, 560, and 575 nm. At pump intensities less than 0.5−1.0 MW/cm 2 , a vibronic photoluminescence band of NV centers in the negative charge state was observed. With an increase in the pump intensity above 0.5−1.0 MW/cm 2 , a superluminescence band was observed on the long-wavelength shoulder of the phonon wing in the range of 700−760 nm. The superluminescence band intensity increased with the pump intensity. It is shown that the position of the superluminescence band with maxima in the range of 715−720 nm remains unchanged at all optical pump wavelengths.