Raman-excited spin coherences in nitrogen-vacancy color centers in diamond

Raman-excited spin coherences were experimentally observed in nitrogen-vacancy (N-V) diamond color centers by means of nondegenerate four-wave mixing and electromagnetically induced transparency. The maximal absorption suppression was found to be 17%, which corresponds to 70% of what is possible given the random geometric orientation of the N-V center in diamond. In the context of quantum computing in solids, this level of transparency represents efficient preparation of quantum bits, as well as the ability to perform arbitrary single-quantum-bit rotations.     

Synthesis and doping of microcolumn diamond photoemitters with silicon-vacancy color centers

Bulletin of the Lebedev Physics Institute - The method of epitaxial growth of localized photoluminescence sources in the form of the ordered microcolumn diamond structures with silicon-vacancy...     

Laser stimulated luminescence in KCl and NaF containing color centers

A broad luminescence band was found in laser irradiated KCl and NaF crystal containing color centers. This emission extends on both sides of the laser line and is interpreted as “hot” fluorescence due to radiative retrapping of laser ionized color centers.     

Photon antibunching in the fluorescence of individual color centers in diamond

We observed photon antibunching in the fluorescent light emitted from a single nitrogen-vacancy center in diamond at room temperature. The possibility of generating triggerable single photons with such a solid-state system is discussed.     

Oscillator strength calculations in color centers of diamond and the role of spin

A generalized Hubbard model based on a molecular approach is used to calculate many electron wavefunctions of diamond vacancies. We have calculated the oscillator strength of the dipole transition rates from the ground states of the neutral and negatively charged vacancies. The ratio of the oscillator strengths is in very good quantitative agreement with the reported optical spectroscopic data. Electronic configurations in the ground and dipole allowed excited states are presented. With the proposed picture, the much larger oscillator strength of the negatively charged vacancy with respect to other experimentally investigated color centers N-V, H3, N3 and H4 is explained.Received: 9 March 2004, Published online: 23 July 2004PACS: 61.72.Bb Theories and models of crystal defects - 61.72.Ji Point defects (vacancies, interstitials, color centers, etc.) and defect clusters - 71.55.-i Impurity and defect levels     

Peculiarities of absorption and luminescence spectra of nitrogen-vacancy color centers in diamond crystals

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 NV⁰ 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.     

Quantum repeater based on NV + 13C color centers in diamond

We suggest a specific way to realize the quantum repeater protocol based on NV + ¹³C defects in diamond and feasible with present techniques. Numerical simulation shows the efficiency of the considered realization in respect of both fidelity of final entangled state and time of its creation, under the condition of using small Rabi frequencies and resonant-only operational pulses. The text was submitted by the authors in English.     

Dependence of nitrogen vacancy color centers on nitrogen concentration in synthetic diamond

Crystallization of diamond with different nitrogen concentrations was carried out with a FeNiCo-C system at pressure of 6.5 GPa. As the nitrogen concentration in diamond increased, the color of the synthesized diamond crystals changed from colorless to yellow and finally to atrovirens (a dark green). All the Raman peaks for the obtained crystals were located at about 1330 cm^-1 and contained only the sp³ hybrid diamond phase. Based on Fourier transform infrared results, the nitrogen concentration of the colorless diamond was < 1 ppm and absorption peaks corresponding to nitrogen impurities were not detected. However, the C-center nitrogen concentration of the atrovirens diamond reached 1030 ppm and the value of A-center nitrogen was approximately 180 ppm with a characteristic absorption peak at 1282 cm^-1. Furthermore, neither the NV⁰ nor the NV^- optical color center existed in diamond crystal with nitrogen impurities of less than 1 ppm by photoluminescence measurement. However, Ni-related centers located at 695 nm and 793.6 nm were observed in colorless diamond. The NE8 color center at 793.6 nm has more potential for application than the common NV centers. NV⁰ and NV^- optical color centers coexist in diamond without any additives in the synthesis system. Importantly, only the NV^- color center was noticed in diamond with a higher nitrogen concentration, which maximized optimization of the NV^-/NV⁰ ratio in the diamond structure. This study has provided a new way to prepare diamond containing only NV^- optical color centers.     

Photo-induced creation of nitrogen-related color centers in diamond nanocrystals under femtosecond illumination

Diamond nanocrystals deposited on a dielectric mirror at the focus of a microscope objective have been illuminated by femtosecond laser pulses. We have observed the photo-creation of color centers, under peak power corresponding to an intensity of about . In a nanocrystal initially containing a single Nitrogen Vacancy (NV) center, femtosecond illumination resulted in the transformation of this center into another one with different spectral features. These features are tentatively attributed to the neutral form NV⁰. This irreversible transformation goes together with the photocreation of other unstable color centers at the laser focus. Such behavior under femtosecond laser illumination place some limitations on the use of sub-picosecond pulses to trigger single photon emission from a single NV center in diamond nanocrystal.     

Thermally activated structural changes in KCl crystals containing color centers

Structural changes taking place in the temperature interval 300–750K in KCl crystals additively colored in Na vapor are studied by spectrophotometric and light scattering methods in conjunction with crystal lattice constant measurement.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 39–45, September, 1984.     

Photoluminescence of SiV centers in CVD diamond particles with specific crystallographic planes

We prepared the isolated micrometer-sized diamond particles without seeding on the substrate in hot filament chemical vapor deposition. The diamond particles with specific crystallographic planes and strong silicon-vacancy(SiV) photoluminescence(PL) have been prepared by adjusting the growth pressure. As the growth pressure increases from 2.5 to 3.5 kPa,the diamond particles transit from composite planes of {100} and {111} to only smooth {111} planes. The {111}-faceted diamond particles present better crystal quality and stronger normalized intensity of SiV PL with a narrower bandwidth of 5 nm. Raman depth profiles show that the SiV centers are more likely to be formed on the near-surface areas of the diamond particles, which have poorer crystal quality and greater lattice stress than the inner areas. Complex lattice stress environment in the near-surface areas broadens the bandwidth of SiV PL peak. These results provide a feasible method to prepare diamond particles with specific crystallographic planes and stronger SiV PL.     

First-principles study on electronic states of SrWO4 crystals containing F-type color centers

The electronic structures of the SrWO₄ crystals containing F-type color centers are studied within the framework of the fully relativistic self-consistent Dirac–Slater theory using a numerically discrete variational (DV-X^α) method. The calculations indicate that either F or F⁺ center has donor energy level within the forbidden band. The electronic transition energies from the two donor levels to the bottom of the conduction band are 1.82 eV and 2.28 eV corresponding to the 685 nm and 545 nm absorption bands, respectively. It is, therefore, concluded that the 545–685 nm absorption bands are originated from the F and F⁺ center in SrWO₄ crystal respectively.     

Aerosol deposition of detonation nanodiamonds used as nucleation centers for the growth of nanocrystalline diamond films and isolated particles

The aerosol deposition of detonation nanodiamonds (DNDs) on a silicon substrate is comprehensively studied, and the possibility of subsequent growth of nanocrystalline diamond films and isolated particles on substrates coated with DNDs is demonstrated. It is shown that a change in the deposition time and the weight concentration of DNDs in a suspension in the range 0.001–1% results in a change in the shape of DND agglomerates and their number per unit substrate surface area N _s from 10⁸ to 10¹¹ cm⁻². Submicron isolated diamond particles are grown on a substrate coated with DND agglomerates at N _s ≈ 108 cm⁻² using microwave plasma-enhanced chemical vapor deposition. At N _s ≈ 10¹⁰ cm⁻², thin (∼100 nm) nanodiamond films with a root-mean-square surface roughness less than 15 nm are grown.     

NV centers in diamond: Quantum-chemical modeling

Quantum-chemical modeling is used to study the relationship between the spin states of nitrogen vacancy (NV) centers and their position on a (100) surface or in the bulk of a diamond crystal. The spin density of the NV centers is computed, and the position of the centers on the crystal surface is demonstrated to be energetically more favorable. The (100) surface of diamond crystal is found to affect the geometrical parameters and adsorption properties of NV centers and their spin-density distribution, relative to these properties in the bulk.     

Transient color centers in GGG crystals

Electron pulse induced absorption and their decay kinetics have been investigated in samples of GGG crystals with different starting absorption spectra. It is shown that for all samples there appears a wide transient absorption (TA) band with two maxima in the region 14,000-17,000 v cm m 1 and 22,000-26,000 v cm m 1 . TA decay kinetics measurements in 14,000 v cm m 1 and 22,000 v cm m 1 are two-exponential (with half-time order several tens and several hundreds ns). Analyzing the obtained results, we can suppose that low and high energy TA bands are connected with the F + (or O m ) and F transient color centers (TCC) respectively.     

First-principles study on electronic structures of BaWO4 crystals containing F-type color centers

The electronic structures of BaWO₄ crystals containing F-type color centers are studied within the framework of the fully relativistic self-consistent Dirac-Slater theory, using a numerically discrete variational (DV-Xα) method. It is concluded that F and F⁺ color centers have donor energy level in the forbidden band. The optical transition energies are 2.449 and 3.101 eV, which correspond to the 507 and 400 nm absorption bands, respectively. It is predicted that 400-550 nm absorption bands originate from the F and F⁺ color centers in BaWO₄ crystals.