Идентификация NV-центров в синтетических флуоресцентных наноалмазах и контроль дефектности кристаллитов методом электронного парамагнитного резонанса

A 100 nm synthetic diamond particle with a large (> 4 ppm) amount of nitrogen vacancy (NV) centers has been studied. The latter exhibit lines associated with forbidden Delta m_s = 2 and allowed Delta m_s = 1 transitions in the electron paramagnetic resonance (EPR) spectra of the ground state of the NV(-) center. The luminescence intensity of particles in the range 550-800 nm increases with an increase in the irradiation dose of 5 MeV electrons and correlates with the integrated intensity of the EPR line with a g-factor g = 4.27.This value is used to estimate the concentration of NV(-) centers and to select diamond powders with the highest fluorescence intensity. The dependence of the EPR signal intensity of the Delta m_s = 2 transition of the NV(-) center on the microwave power has the form of a curve with saturation and subsequent decay, and rather well characterizes the crystal quality of the local environment of the centers under study in these particles. The intensity of the x,y Delta m_s = 1 transition (at ~281.2 mT, 9.444 GHz) turns out to be more sensitive to changes in particle size in the submicron range and the appearance of near-surface defects obtained during mechanical processing.

Stacked metasurfaces for enhancing the emission and extraction rate of single nitrogen-vacancy centers in nanodiamond

Dielectric metasurfaces with unique possibilities of manipulating light-matter interaction lead to new insights in exploring spontaneous emission control using single quantum emitters. Here, we study the stacked metasurfaces in one- (1D) and two-dimensions (2D) to enhance the emission rate of a single quantum emitter using the associated optical resonances. The 1D structures with stacked bilayers are investigated to exhibit Tamm plasmon resonance optimized at the zero phonon line (ZPL) of the negative nitrogen-vacancy (NV-) center. The 2D stacked metasurface comprising of two-slots silicon nano-disks is studied for the Kerker condition at ZPL wavelength. The far-field radiation plots for the 1D and 2D stacked metasurfaces show an increased extraction efficiency rate for the NV- center at ZPL wavelength that reciprocates the localized electric field intensity. The modified local density of optical states results in large Purcell enhancement of 3.8 times and 25 times for the single NV- center integrated with 1D and 2D stacked metasurface, respectively. These results have implications in exploring stacked metasurfaces for applications such as single photon generation and CMOS compatible light sources for on-demand chip integration.

MANIFESTATION IN IR-LUMINESCENCE OF THE CROSS RELAXATION PROCESSES BETWEEN NV CENTERS IN WEAK MAGNETIC FIELDS

We present a combined experimental and theoretical study of the effect of magnetic field on the luminescence from an ensemble of NV centers in diamond. It was found that the intensity of infrared luminescence associated with transitions between singlet levels of NV centers shows a pronounced increase of a near-zero magnetic field. The influence of the power and polarization of laser radiation on the amplitude and shape of the revealed local maximum in IR-luminescence of NV centers is investigated. An eight-level photophysical model of an NV center in the presence of an arbitrarily directed magnetic field has been constructed and on its basis the calculation has been performed of the luminescence intensity emitted by an ensemble of NV center, both in the visible and infrared regions of the spectrum. It is shown that the phenomenological allowance for the cross-relaxation of NV centers between each other and with other paramagnetic centers in a diamond within the framework of this model allows describing the experimentally observed fluorescence features of an ensemble of NV centers in the presence of weak magnetic fields.

Directional luminescence of the diamond NV center via Bloch surface waves in one-dimensional photonic crystals

In this work, we numerically study the luminescence of nanodiamonds with NV centres embedded in a polymer layer on the surface of one-dimensional photonic crystal. The interaction of NV center spontaneous emission with the Bloch surface wave (BSW) is demonstrated. The presence of a photonic crystal leads to a change in the angular distribution of the emitter radiation due to the coupling of luminescence to BSW. We show that the best coupling efficiency of 71% is observed when NV centres are located in the close proximity to the BSW field maximum.