We have studied photoluminescence spectra of nitrogen-vacancy (NV) centers upon their pumping by short-wavelength visible and near-UV radiation. We have shown that NV 0 centers, as distinct from NV − centers have an absorption line in the UV range. Inversion of the zero-phonon line of NV − centers has been shown and interpreted.
The optical and ODMR spectra of nitrogen vacancy (NV) centers in diamond were investigated as applied to the development of micro-scale diamond magnetometer sensor. It is shown that the NV 0 center (unlike the NV − center) has an absorption line in the UV range. The inversion of the zero phonon line of the NV − center was observed and explained. ODMR signals in high magnetic fields (as compared with inner fields in the crystal) as well as in weak fields also were investigated. We propose the solution to the problem of the magnetometer sensitivity reduction at low magnetic field, that is of interest for quantum magnetometry applications.
We report on the spectroscopic and laser characterization of negatively charged nitrogen-vacancy (NV−) centers in diamond. Spectroscopic properties such as absorption and emission spectra as well as kinetics were studied, and parameters such as cross-sections and lifetimes were estimated. A vibronic band of NV0 with zero phonon line (ZPL) at 575 nm was detected under 532 nm pulsed excitation due to the photoionization of NV−. Transmission of 532 nm pump pulses saturate around ∼10%, which is much smaller than the theoretical level. Δk/k0 kinetics revealed slow recovery of NV− centers after photoionization under 532 nm pumping, which involved different relaxation channels depending on the probe beam wavelengths. Localization of the electrons in the metastable state of NV0 centers resulted in higher saturated transmission of 632 nm pump.
Abstract In the context of the NV− diamond laser creation [1], an urgent task is to determine the characteristics of diamonds that can affect the 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 = 532nm). It was found that when the HPHT diamond is irradiated by 532 nm radiation with an intensity above ~ 2.0 MW/cm2, 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 increasing 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/cm2 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.
The effect of laser radiation with a wavelength near 1.55 µm on the photoluminescence properties of “nitrogen-vacancy” (NV) color centers in diamond has been studied experimentally. The effect of radiation of an infrared laser on the charge state of color centers redistributes the spectral intensity of photoluminescence in the ensemble of NV centers. In the case of neutral NV centers, the quenching of photoluminescence reaching about 60% has been observed. A feature of the laser excitation of NV centers by this method is the absence of competition with stimulated emission and two-photon excitation, which is observed with an increase in the power of infrared radiation at other wavelengths.
Abstract The ultraviolet-visible (UV-Vis) spectrum was not generally considered an available method for measuring the concentration of negatively charged nitrogen-vacancy (NV-, NV center). In this study, we propose the idea of evaluating the concentration of NV center by the slope of the UV-Vis spectrum. To establish this new method we synthesized diamonds with different NV center concentrations by the chemical vapor deposition (CVD) method. We then measured the zero-phonon line (ZPL) intensity of PL spectra at 637 nm and estimated the concentration of the NV centers as a baseline for comparison to our new UV-Vis method. The UV-Vis transmission spectra were then measured and transformed to relative absorption coefficient spectra. Slopes of the transformed UV-Vis spectra between 400 nm and 800 nm were calculated and compared with the ZPL intensities. The results show a strong positive correlation between the slopes of the absorption spectra and the ZPL intensities of PL spectra at 637 nm. Therefore, this paper demonstrates the feasibility of estimating the concentration of the NV centers from measuring the transmission UV-Vis spectrum.
The photoluminescence spectra of two synthetic diamond samples containing 1-10 ppm 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/cm2, 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/cm2, a superluminescence band was observed on the long-wavelength shoulder of the phonon wing in the range 700-760 nm. The intensity of superluminescence band increased with increasing pump intensity. It is shown that the position of the superluminescence band with maxima in the range 715-720 nm is unchanged at all of optical pump wavelengths.