Color Centers In Crystals Research Articles

Defect Healing of Micro/Nanocrystals via the Coordination Competition of Rare Earth in Crystal Engineering.

Defect engineering has been generally observed and utilized in crystal materials including metal oxides, metal-organic frameworks, and so on; however, how to relate the defect formation and crystallization process is needed to be revealed clearly, and how to heal the defect is a big challenge. Herein, based on the new coordination complex (HNU-53), the crystal defects were created by increasing the reaction time and crystal size. Following the crystal growth process, the crystal color centers were simultaneously generated, resulting in fluorescence quenching. To heal the defect, the crystal growth was controlled by the introduction of rare earth ions. With the coordination competition of rare earth ions, the crystal defects were reduced and recovery of fluorescence emission was achieved.

Single quantum emitters detection with amateur CCD: Comparison to a scientific-grade camera

Fluorescence imaging of single quantum light emitters (atoms, molecules, quantum dots, color centers in crystals) is an inherent experimental problem of modern photonics and its numerous applications. In these measurements, highly sensitive cameras are of the key significance. Recent progress in technologies of charge-coupling devices (CCD) and complementary metal-oxide semiconductor (CMOS) sensors opens up possibilities for detection of extreme low light signals up to a single photon counting. Here, we investigate the parameters of high-professional scientific- and amateur-grade cameras in the view of their use in the fluorescence nanoscopy with the detection of single molecules and, in general, quantum emitters of different nature. A series of photoluminescence imaging experiments have been conducted with single colloidal semiconductor core-shell nanocrystals CdSeS/ZnS (quantum dots, QD), which are usually considered as a basis of various sensors and actuators technologies. We find parameters of the experiment for the amateur-grade camera to obtain images of single QDs with signal-to-noise ratio compared to the scientific-grade camera at exposure times ranging from 1s to 1000s.

Zero-Phonon Transition Frequency in Diffuse Electronic Spectra of Color Centers in Crystals and Glasses

The method for determining frequencies of purely electronic molecular transitions from diffuse electronic absorption or emission spectra that is based on an adiabatic approximation and thermal equilibrium in the initial transition state is shown to be applicable to color centers and F-centers in crystals and glasses. The experimental results showed that the method can be used, in particular, to monitor the homogeneity of chromophores and, possibly, the media containing them.

Multifunctional far-field luminescence nanoscope for studying single molecules and quantum dots: (50th anniversary of the Institute of Spectroscopy, Russian Academy of Sciences)

Far-field fluorescence spectromicroscopy of single quantum emitters (SQEs) (single molecules, quantum dots, color centers in crystals) is an actively developing field of modern photonics, which is in widespread demand in various applications in physics, chemistry, material sciences, life sciences, and quantum technologies. In this paper, we present a description of a multifunctional experimental setup which was developed in recent years at the Institute for Spectroscopy of the Russian Academy of Sciences. It allows measuring optical spectra and fluorescence images of SQEs, as well as their temporal behavior and luminescence kinetics, in a broad range of temperatures (from cryogenic to ambient). It is shown that the spatial coordinates of SQEs can be reconstructed with subdiffractional accuracy (up to a few angstroms). Some examples of the developed methods for multiparameter superresolution microscopy (nanoscopy) of materials and nanostructures are presented.

Ultrafast Room-Temperature Single Photon Emission from Quantum Dots Coupled to Plasmonic Nanocavities.

Efficient and bright single photon sources at room temperature are critical components for quantum information systems such as quantum key distribution, quantum state teleportation, and quantum computation. However, the intrinsic radiative lifetime of quantum emitters is typically ∼10 ns, which severely limits the maximum single photon emission rate and thus entanglement rates. Here, we demonstrate the regime of ultrafast spontaneous emission (∼10 ps) from a single quantum emitter coupled to a plasmonic nanocavity at room temperature. The nanocavity integrated with a single colloidal semiconductor quantum dot produces a 540-fold decrease in the emission lifetime and a simultaneous 1900-fold increase in the total emission intensity. At the same time, the nanocavity acts as a highly efficient optical antenna directing the emission into a single lobe normal to the surface. This plasmonic platform is a versatile geometry into which a variety of other quantum emitters, such as crystal color centers, can be integrated for directional, room-temperature single photon emission rates exceeding 80 GHz.

Color centers in YAG

Yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG) is one of the most important optical materials with many existing and potential future applications in laser, illumination, and scintillation. X-rays, g-rays, and UV light can induce ionization and significant changes in the valency of impurities and defects in YAG single crystals which may lead to the formation of color centers. In fact, the use of YAG crystals in laser and scintillation devices involves significant formation of color centers and requires full understanding for their characteristics and effects on the material properties. In this work, the formation and characteristics of color centers in undoped and rare-earth doped YAG single crystals was investigated mainly through optical absorption spectroscopy. An increase in the absorption over a broad range of wavelengths was observed in the as-grown sample after UV irradiation. F-centers and iron impurities in the as-grown undoped crystals were found to be responsible for the formation of color centers. However, air- or oxygen-anneal seems to be effective in suppressing most color centers in the crystals.

Two-dimensional metal inclusions in a dielectric crystal

Highly aggregated color centers in crystals of a wide-band-gap calcium fluoride insulator heated in a reducing atmosphere of vapors of calcium metal cation (“additive coloration” of crystals) have been studied using spectroscopy and atomic-force microscopy methods. These centers are large aggregates of anion vacancies and electrons, which transform into metal structures. The evolution of these structures with increasing number of such components has been traced from individual particles with two-dimensional structure to large film fragments. It has been shown that fragments are concentrated in isolated planes {111}, which are cleavage planes of the crystal with high contents of highly aggregated centers.

Additive coloring of CaF2 optical ceramic

The specificity of additive coloring of CaF2 optical ceramic (formation of color centers in it and photothermochemical transformation of these centers in colored ceramic samples) has been considered. Under the same coloring conditions, this process occurs more slowly in ceramics rather than in crystals; at the same time, the limiting concentration of color centers that can be introduced into ceramics is much higher. The photothermochemical transformations of color centers in crystals and ceramics, which occur under illumination at different wavelengths and upon heating, have been studied. The specific features of introduction of color centers into ceramic and their transformation under illumination and heating are likely to be related to the mass twinning of ceramic grains.

Elementary-oscillator model for color centers with degenerate levels

Quantum transitions between nondegenerate and degenerate (with respect to angular momentum projection) levels of color centers in crystals are described in terms of classical electric-dipole oscillators. It is shown that, upon absorption of elliptically polarized exciting radiation, the system under study transfers to a definite state and the transition is described in general by an elliptical oscillator. An electric-dipole transition accompanied by the creation of a photon is described by a random vector, i.e., by an arbitrary elliptical oscillator lying in the corresponding plane. For an ensemble of n identically oriented centers undergoing a given transition, the luminescence intensity is described by a set of n/2 right-handed rotators and n/2 left-handed rotators. The results obtained are important for solving problems related to quantum information.

Franck−Condon Modes in Sr2MnWO6 Double Perovskite

Molecules and color centers in crystals are known to exhibit a form of electron−phonon coupling, which is understandable by the Franck−Condon mechanism. In a Raman spectrum, this process is seen as a series of equidistant peaks whose relative intensities depend on the induced atomic vibration mode. The process has been predicted to be observable in crystals, but the difficulty in observing them has been related to the fact that the excited electron states tend to be delocalized. Correspondingly, it has been assumed that a self-trapping (localization) of the electron is necessary. Our polarization resonance Raman scattering data revealed two different series of Franck−Condon modes in double perovskite Sr2MnWO6 single crystals. One series corresponded to the Mn d orbital electron transition to the conduction band, whereas the second series corresponded to eg to eg transition (localized electron). The lattice distortion was estimated from the observed Franck−Condon peak positions and intensities.

Using frustrated total internal reflection spectroscopy to study color centers in crystals

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text E. V. Zhukova, V. M. Zolotarev, N. B. Margaryants, and L. P. Shishatskaya, "Using frustrated total internal reflection spectroscopy to study color centers in crystals," J. Opt. Technol. 66, 46- (1999) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Electron-irradiation-induced defects in crystals

We report preliminary results on the production of colour centres in crystals, subjected to electron irradiation. The dependence of the colour-centre creation on the temperature and dose of the irradiation, as well as on the direction of crystal growth, was studied. Our experimental results concerning absorption, emission and excitation spectra measurements show that defect formation in crystals depends strongly on the conditions of crystal growth and preparation of the samples. By comparing with and LiF crystals, we were able to attribute the absorption bands at 260, 420, 632, 386 and 480 nm to F, and centres. Theoretical evaluations of the absorption energies for these defects were made, and they supported these assignments. Room temperature electron irradiation of crystals grown in and directions favours the formation of different kinds of F-aggregate centre for each of these two cases. In particular, for crystals we were able to observe the formation of centres with one absorption band at 632 nm and a corresponding emission at 702 nm.

Polarization dependence of luminescence induced by two-photon excitation in LiF crystals with F 3 + laser color centers and the symmetry of the excited state

The energy level structure of F3+ laser color centers in crystals of LiF is discussed. A high-power laser (λex=920 nm) is used to excite luminescence from LiF crystals with F3+ centers via two-photon absorption, and the dependence of the polarization and intensity of this luminescence on the polarization of the laser light is measured and calculated. It is shown that the two-photon transition involves the excitation of a previously unknown state of the F3+ center—a spin singlet whose wave function has 1A1 symmetry.

Intracavity spectroscopy utilizing lasers based on $F^-_2$ color centers in LiF crystals

A description is given of an intracavity spectroscopic system based on a laser utilizing F2- color centers in a crystal of LiF and operating in the free-running regime emitting at wavelengths in the range 1.1–1.25 μ. The color-center laser was pumped by a neodymium laser. The absorption spectra of water vapor, methane, and ammonia were recorded.

Growth and light-induced colour centres in crystals of Yttrium aluminum garnet doped with Cr 3+ ions

Growth- and light-induced colour centres (GCC and LCC) in yttrium aluminium garnet crystals doped with chromium Y 3Al 5O 12:Cr 3+) have been studied. Optical absorption and liuminescence spectra of the crystals with GCC and LCC were measured. GCC absorption spectrum consists of four wide bands at 285, 310, 335 and 446 nm. Annealing in a hydrogen atmosphere destroys successively absorption bands at 446 and 335 mm. There are two wide bands in the LCC absorption spectrum at 380 and 480 nm. GCC and LCC disappear when crystals are annealed in an oxidation atmosphere.