For the first time, lasing at NV− centers in an optically pumped diamond sample is achieved. A nanosecond train of 150-ps 532-nm laser pulses was used to pump the sample. The lasing pulses have central wavelength at 720 nm with a spectrum width of 20 nm, 1-ns duration and total energy around 10 nJ. In a pump-probe scheme, we investigate lasing conditions and gain saturation due to NV− ionization and NV0 concentration growth under high-power laser pulse pumping of diamond crystal.

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Superluminescence of NV centres with a band peaking at λ = 718 nm in the phonon wing of the photoluminescence spectrum of a high-pressure high-temperature (HPHT) diamond sample under pulsed optical excitation at λ = 532 nm with an intensity of 2 – 46 MW cm-2 is demonstrated. Superluminescence is observed in the diamond crystal region containing 6 ppm NV centres and 150 ppm substituent nitrogen; it is absent in the crystal part with a lower nitrogen content. Superluminescence pulses are observed on the leading edge of the optical excitation pulse at λ = 532 nm and have an FWHM value of 4 ns. The enhancement of the photoluminescence of NV centres is suggested to be due to the total internal reflection in the diamond plate (waveguide effect).