A. M. Tkachuk

New laser crystals based on KPb2Cl5 for IR region

Abstract The KPb2Cl5 single crystals, doped by different Rare Earth ions were grown. The RE segregation coefficient was found to decrease from 1.0 to 0.15 in the set from Nd to Yb. Spectroscopic properties and luminescence decay were studied, stimulated emission was demonstrated at 1.06 μm (Nd3+) and at 2.43 μm (Dy3+).

Spectroscopic studies of erbium-doped potassium-lead double chloride crystals KPb2Cl5:Er3+: 1. Optical spectra and relaxation of excited states of the erbium ion in potassium-lead double chloride crystals

Optical spectra, intensities of radiative and nonradiative transitions, and luminescence kinetics in erbium-doped potassium-lead double chloride crystals KPb2Cl5:Er3+s(KPC:Er3+) were investigated. The crystals were grown by the Bridgman-Stockbarger method. Their absorption and luminescence spectra were studied experimentally. The crystal-matrix absorption edge was determined at 80 and 300 K. Intensity parameters, radiative transition probabilities, branching ratios, and nonradiative relaxation rates were estimated by the Judd-Ofelt method. The luminescence kinetics from the emitting levels 4G11/2, 2G9/2, 4S3/2, and 4F9/2 upon selective excitation was studied.

Quantum dynamics of atomic magnets: cotunneling and dipolar-biased tunneling.

Multispin tunneling cross relaxations in an ensemble of weakly coupled Ho3+ ions, mediated by weak anisotropic dipolar interactions, can be evidenced by ac-susceptibility measurements in a high temperature regime. Based on a four-body representation, including the rare-earth nuclear spin, two-ion tunneling mechanisms can be attributed to both dipolar-biased tunneling and cotunneling processes. The coreversal involving entangled pairs of magnetic moments is discussed with a particular emphasis, giving new evidence to elucidate the many-body quantum dynamics in dipolar spin glasses.

Spectral and dynamic study of the broad band UV 4f25d→4f3 emission in Nd-doped double sodium yttrium fluoride crystals and comparison with Nd:LiYF4

Abstract VUV and UV spectroscopy of 4f 2 5d excited configuration of Nd 3+ ions has been investigated in the double sodium yttrium fluoride crystal Na 0.4 Y 0.6 F 2.2 . The spectral and dynamic properties of Nd 3+ in this disordered structure are compared to those observed for Nd 3+ :LiYF 4 .

Spectroscopic study of double sodium-yttrium fluoride crystals doped with erbium Na0.4Y0.6F2.2:Er3+: I. Intensities of luminescence spectra and kinetics of luminescence

Na0.4Y0.6F2.2:Er3+ (NYF:Er) crystals with an erbium concentration as high as 100 at. % (Na0.4Er0.6F2.2) were grown by the Bridgman-Stockbarger method. The optical spectra were investigated at low (6 K) and room temperatures. It is shown that the absorption spectrum of NYF:Er crystals contains wide bands (790–801 and 965–980 nm) corresponding to the emission range of laser diodes. The peak absorption cross section σa for the band peaked at λ=970.4 nm is 0.15×10−20 cm2. On the basis of the analysis of the absorption and luminescence spectra at low (6 and 12 K) temperatures, the structure of the Stark splitting of erbium levels was determined as a structure of quasi-centers for which Stark components are inhomogeneously broadened. The oscillator strengths of the transitions from the ground state of erbium to excited multiplets were calculated from the absorption spectra measured at T=300 K, and the intensity parameters Ωt were determined by the Judd-Ofelt method: Ω2=1.65×10−20 cm2, Ω4=0.56× 10−20 cm2, and Ω6=1.01×10−20 cm2. These values of the intensity parameters were used to calculate the probabilities of radiative transitions and the branching ratios. The rates of multiphonon nonradiative transitions in NYF: Er were estimated. The luminescence decay kinetics for radiative levels of erbium ions upon their selective excitation by nanosecond laser pulses was studied. The intracenter lifetimes of radiative levels of erbium ions were determined from the luminescence kinetics upon selective ion excitation by low-intensity light in a sample with a low erbium concentration (0.5%). It is demonstrated that, with an increase in temperature from 6 to 300 K, luminescence from the 4G11/2, 2G(H)9/2, and 4F9/2 levels is quenched as a result of multiphonon nonradiative transitions. Luminescence from the 4I9/2 level is quenched only insignificantly with increasing temperature, and no quenching of luminescence from the 4I11/2 and 4I13/2 levels is observed. The spectra of steady-state luminescence of NYF:Er(0.5–15%) crystals were investigated upon broadband excitation by UV and UV-visible lamp light and selective time-resolved laser excitation. It is shown that low-lying levels of erbium ions separated by an energy gap smaller than 2500 cm−1 are populated via cascade mechanisms. On the basis of the results obtained, it is concluded that NYF:Er3+ crystals are promising candidates for active media of tunable diode-pumped lasers.

Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+

Frequency and dc magnetic field dependences of dynamic susceptibility in diluted paramagnets

New low-phonon frequency crystals based on rare-earth-doped double halogenides for multiwavelength diode-pumped solid state lasers

\mathrm{Li}\mathrm{Y}{\mathrm{F}}_{4}:{\mathrm{Ho}}^{3+}

Spectroscopic study of neodymium-doped potassium-lead double chloride Nd3+:KPb2Cl5 crystals

have been measured at liquid helium temperatures in ac and dc magnetic fields parallel to the symmetry axis of a tetragonal crystal lattice. Experimental data are analyzed in the framework of the microscopic theory of relaxation rates in the manifold of 24 electron-nuclear sublevels of the lowest non-Kramers doublet and the first excited singlet in the

Spectral-luminescent properties of Tm:YLF crystal

{\mathrm{Ho}}^{3+}

Cascade-avalanche up-conversion in Tm3+:YLF crystals

ground multiplet