Yurii V. Orlovskii

Multiphonon nonradiative relaxation from high-lying levels of Nd3+ ions in flouride and oxide laser materials

Abstract Here we report on the results of systematic investigation of multiphonon nonradiative relaxation from high-lying levels 4F 9 2 , 4G 5 2 , 4G 7 2 , 4D 3 2 and 2P 3 2 of Nd3+ ion in fluoride matri ces (fluoride glass, LaF3, CaF2, SrF2, YLiF4) and oxide matrices (Gd3Ga5O12, YAlO3, CaMoO4, Y3Al5O12) with a concentration of Nd3+ near 1%. New quantitative data on relaxation rates for some nonradiative transitions were obtained in these laser materials. The energy gap dependence of nonradiative relaxation rate was measured and analyzed in LaF3, YLiF4, Gd3Ga5O12, YAlO3, CaMoO4 and Y3Al5O12 crystals in 1100–2200 cm−1 energy gap region. The slope of energy gap dependencies for fluoride matrices was found to be larger than for oxide matrices. Our experimental data give values of nonradiative relaxation rates in the small energy gap region of 400–2500 cm−1 close to the data obtained from one-phonon broadening of luminescence spectral lines. Also the luminescence spectra for transitions from the 4G7/2, 4D3/2, 2P3/2 levels are presented.

Novel laser breakdown spectrometer for environmental monitoring

A novel experimental set-up using laser-induced breakdown spectroscopy (LIBS) for environmental analyses of heavy metals is described in this paper. It is based on state-of-the-art spectroscopic equipment, advanced detectors, and laser atomizers: a 0.75 m spectrometer ARC-750, intensified TE- cooled 256 X 1024 CCD camera, probe with fiber optic guide for signal transportation, and Nd:YAG laser plasma atomizers with two different methods for sample delivery. In the first method the liquid solution containing the atoms to be investigated is drawn into the chamber of the nebulizer. The mixture passes through the nozzle, accompanied by argon gas along with formed aerosol, and enters the plasma plume, which is generated by the laser spark in argon. The second method is based on direct generating of the plasma in the water jet of a continuously circulating sample. LIBS testing of samples containing Al, Cd, Cu, Fe, Pb, Zn, and Cr ions was compared with results using atomic absorption spectrophotometry. Initial indications showed good agreement between these two methods. Detection levels of less than 100 ppb were observed for copper and chromium. The described spectroscopic system exhibits high sensitivity, accumulation of luminescence spectrum in real time; and high dynamic range for concentrations detection from 100 ppb to 1000 ppm.

Cooperative optical phenomena in praseodymium doped CsCdBr3

In CsCdBr3 the trivalent Rare-Earth (RE) ions substitute for the divalent Cd ions. For reasons of charge compensation and the specific crystal structure, RE centers of the form RE3+ - (Cd vacancy) - RE3+ are preferentially formed. These symmetric pair centers are very suitable for studying cooperative effects of RE ions. These include processes between the ions of the pair as well as processes between the coupled pair and the electronic excitations of the host lattice. Experiments will be shown and discussed on: (i) cross relaxation and up-conversion by direct ion-ion interaction; (ii) cooperative cross relaxation of the Pr3+ pairs with the host lattice; and (iii) cooperative vibronic emission of the Pr3+ pairs with high phonon progressions.

Nonradiative relaxation and inhomogeneous splitting of aggregated optical centers in the Nd3+-doped CaF2 and SrF2 crystals (FLN and decay study)

Site-selective fluorescence and laser excitation spectroscopy for different types of optical centers in SrF 2 : Nd 3 + (0.3 -1.0%) and SrF 2 : La 3 + (1.0%): Nd 3 + (0.2%) were performed at 4.2 K. The crystal-field levels of the 4 I 9/2 , 4 F 3/2 , and 4 G 5/2 multiplets for different Nd 3+ optical centers were determined in SrF 2 : Nd 3 + (0.3%). An attempt was made to identify some of the new optical centers on the basis of their fluorescence lifetimes and crystal-field splitting. Some models of these centers have been discussed. Two-six times reduction of the 4 F 3/2 multiplet lifetime was observed in the pair M-center in comparison with the single optical centers due to energy cross-relaxation in the pair. A fine splitting of the levels at the 4 I 9/2 (1) → 4 G 5/2 (1) crystal-field transition (1.5 cm -1 ) similar to that in CaF 2 (2.4 cm -1 ) was found for the Nd-Nd pair in SrF 2 . The variation of the splitting from CaF 2 to SrF 2 nicely demonstrates the R -5 dependence of coherent quadrupole-quadrupole interaction.

Laser-induced fluorescence spectrometer based on tunable color center laser for low-impurity-solution diagnostic and analysis

Solid state (SS) tunable LiF:F2 color center laser with second and fourth harmonic generation for visible and ultra violet spectral ranges was developed for the laser induced fluorescence spectroscopy (LIFS). The construction and properties of excitation, registration and flame atomization systems for water solution diagnostic are discussed. The testing experiment with low iron concentrated water sample exhibits ultrahigh sensitivity which was estimated to be 0.05 ppb in our set-up. The SS LIFS spectrometer developed is usable to measure more than 42 metal elements in solution on the ppm, ppb level for various medical and biological applications.

Stimulated emission of laser dyes in opal — like matrix (photonic crystal) under nanosecond pulsed laser excitation

Transformation of fluorescence to stimulated emission in synthetic opals with voids filled by ethanol solutions of organic dyes is studied. Simultaneous shift of fluorescence and laser spectra maxima because of Bragg reflection is observed.

New Regularity of Multiphonon Relaxation in Rare Earth Doped Laser Crystals

Dependence of multiphonon relaxation rate of mid-IR transitions of rare-earth ions on the distance between a rare- earth ion and a nearest ligand in low phonon laser hosts with similar phonon spectra is considered.

Inhomogeneous broadening of the dynamically split Kramers spectral line and up-conversion in the pair and quartet centers in CaF2:Nd3+

The detailed site-selective and time-resolved fluorescence laser spectroscopy and kinetic measurements with high spectral and nanosecond temporal resolution were applied to analyze the M and N absorption bands at the 4I9/2(1) yields 4G5/2(1) crystal field (CF) transition in the CaF2:Nd3+ crystal at 4.2 K. It was found that at helium temperatures the dynamically split spectral line at the 4I9/2(1) yields 4G5/2(1) CF transition of coherently coupled Nd3+ ions in the pair M- and quartet N-centers is inhomogeneously broadened. Small variation of fluorescence lifetimes of the 4F3/2 and 4D3/2 levels due to small variation of distances between Nd3+ ions in the pairs was found. Approximately 1 percent variation of the Nd-Nd distance in the pair -center was determined form lifetime variation of the 4F3/2 manifold.

Laser-induced fluorescence spectrometer based on solid state tunable color-center laser for heavy metal analysis

All solid state (SS) laser induced fluorescence (LIF) spectrometer based on tunable LiF:F2- color center (C.C.) MALSAN laser with second and fourth harmonic generation was optimized for trace metallic concentration measurements in water solutions. Two types of heavy metals atoms Sn and Pb were analyzed using inexpensive low temperature types of the propane/butane-air flames. The maximum sensitivity of 10 and 50 ppb with good linearity of fluorescence intensity concentration dependence was obtained for Sn and Pb atoms, respectively, using a monochromator for the fluorescence wavelength selection. When the monochromator was replaced by a set of color optical filters the sensitivity of 0.3 ppb for Pb atoms was obtained. Hence, the sensitivity was increased more than 150 times for more cheap and simple registration set-up. An attempt was made to use more compact super- broadband LiF:F2- C.C. laser to replace the MALSAN laser in LIF spectrometer. Up to now the sensitivity of 1 ppm for Pb with the monochromator based fluorescence registration system was obtained in the latter case.

Nature of electron excitation-energy transfer Cr3+--TR3+ in garnet crystals

This paper is devoted to the donor (chromium ion) excitation-energy decay caused by interaction with the acceptors (rare earth ions) in garnet crystals, as analyzed within the approximation of a static nonradiative energy transfer.