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The glasses of the composition 20CaF2–xAl2O3–(59-x)P2O5–20SiO2:1.0Ho2O3/1.0Er2O3 and 20CaF2–xAl2O3–(59-x)P2O5–20SiO2:(0.6Ho2O3+0.4Er2O3) with x varying from 2 to 10 mol % have been synthesized. Optical absorption and fluorescence spectra (in the spectral range 350–2100 nm were studied at ambient temperature. The Judd–Ofelt theory was applied to characterize the absorption and luminescence spectra of Ho3+ and Er3+ ions in these glasses. Following the luminescence spectra, various radiative properties like transition probability A, branching ratio β, and the radiative life time τ for blue (B), green (G), and red (R) emission levels of these glasses have been evaluated. The radiative life times for these transitions of Ho3+ and Er3+ have also been measured. The variations observed in these parameters were discussed in the light of varying coordinations (tetrahedral and octahedral positions) of Al3+ ions in the glass network. The energy transfer between the two rare earth ions (Ho3+ and Er3+) in codoped CaF2–Al2O3–P2O5–SiO2 glass system in the visible and near infrared (NIR) regions has also been investigated as a function of varying concentration of Al2O3. A significant enhancement in the intensities of B, G, and R lines has been observed due to codoping. The quantitative analysis of these results (with the aid of the data on IR and Raman spectral studies) has indicated that the glasses mixed with around 6.0 mol % of Al2O3 is the optimum concentration for yielding the highest quantum efficiency and for maximum energy transfer with low phonon losses. [ABSTRACT FROM AUTHOR]

The nanoscale crystals (NCs) of ZnO were embedded into polymethylmethacrylate (PMMA) polymeric matrix and nanocomposite films were prepared by modified spin coating method. The surface of the ZnO/PMMA nanocomposite films has been investigated using atomic force and scanning electron microscopy. The prepared films are highly transparent, the ultraviolet-visible spectra show their high optical quality. The second and third harmonic generation (SHG and THG) studies of ZnO/PMMA nanocomposite films with different concentrations of ZnO NCs were carried out at λ=1.064 μm and the effective values of the second and third order nonlinear susceptibilities were estimated to be higher than that of ZnO bulk for the films at low concentration of ZnO NCs. This could indicate that surface effects in ZnO/PMMA nanocomposite films have a dominant role over bulk effects for the SHG and THG processes. [ABSTRACT FROM AUTHOR]

Influence of lithium tetraborate (Li2B4O7, TBL) glass matrix on the luminescent properties of the Pr+3 ions emission was investigated. It was demonstrated that the decrease of matrix long-range ordering leads to substantial widening of corresponding peaks in the emission spectra in comparison with crystalline Ca4GdO(BO3)3 matrices. During the decrease of temperature from 292 down to 82 K a distinct low-energy spectral shift of the principal red luminescent band from 607 to 610 nm is observed, which is a consequence of a coexistence of several structural borate fragments. Simulations of incorporation the Pr3+ ions into the TBL glasslike matrix were carried out using the Langevin molecular dynamics simulations and quantum chemical simulations. Possibility of partial substitution of boron ions by Pr3+ ions is demonstrated. The contribution of the electron-phonon subsystems to the spectral broadening of the corresponding emission red lines was evaluated. It was shown that the main contribution to the emission bands gives harmonic electron-phonon interactions contrary to the generally adopted model assuming prevailing role of anharmonic electron-phonon interactions. [ABSTRACT FROM AUTHOR]

Substantial photoinduced changes of ultraviolet (UV) -visible (UV-vis) optical spectra were observed for the Au nanoparticles prepared by a “touch” seed-mediated growth technique on the surface of indium-tin-oxide substrate. The phototreatment was performed by two-color coherent laser beams with a wavelength of 1060 nm (fundamental beam) and double frequency 530 nm (writing beam). The maximal photoinduced changes of the UV-vis spectra were observed for the surfaces possessing low resistivity (about 4 Ω/sq). Those of higher resistivity (about 50 Ω/sq) demonstrate only slight shifts of the main Au particle surface-plasmon resonance maxima at λ=570 nm. The effect observed is a consequence of a superposition of optically induced surface plasmon resonance, scattering on optically induced grating and electron-phonon relaxation. [ABSTRACT FROM AUTHOR]

The photoinduced nonlinear optical effects in large-sized (up to 20 nm) Ca[sub 4](GdO(BO[sub 3])[sub 3]) GdCOB nanocrystallites incorporated within an oligoether photopolymer matrix have been studied. The photoinduced optical second harmonic generation (SHG) was measured at the fundamental wavelength 1.06 µm. A nitrogen pulsed laser (λ=0.337 µm) was used as the source of photoinducing light. We found that with increasing ultraviolet (UV) illumination power density, the output doubled frequency SHG signal (λ = 0.53 µm) increases and achieves its maximum value at a UV power density about 1.4 GW/cm² and nanocrystallite size about 5.5 nm. The absolute SHG values were about 15% less than for the d[sub 222] tensor of potassium dihydrogen phosphate single crystals. With decreasing temperature below 18 K, the SHG signal increases. Probe-pump measurements indicate the occurrence of a SHG maximum at a pump-probe delay time of about 27 ps. This effect is explained within the framework of the anharmonic electron-phonon interaction due to creation of photoinduced electrostricted phonons. Third-order two-photon absorption was also investigated. We showed that the BO[sub 3] structural fragments play a crucial role in the observed photoinduced effects. The results obtained show that the mentioned composites can be used as a powerful tool for creation of UV-operated nonlinear optical devices. [ABSTRACT FROM AUTHOR]

Acoustically induced optical second harmonic generation (AIOSHG) in ferroelectric Pb[sub 4.7]Ba[sub 0.3]Ge[sub 3]O[sub 11] (PBG) crystal has been observed. With increasing acoustical power, the AIOSHG for Nd doped yttrium-aluminum garnet laser light (λ = 1.06 µm) increases and achieves its maximum value at acoustical power density of about 1.75 W/cm². The values of the AIOSHG for the PGB are considerably higher than for other photorefractive ferroelectrics. With decreasing temperature, the AIOSHG signal strongly increases below 29 K and correlates well with a ferroelectric phase transition detected by the differential scanning calorimetric method and spontaneous polarization measurements. The AIOSHG maxima were observed at acoustical frequencies lying within the ranges 12-17, 22 to 23, and above 26 kHz. Comparing the obtained results with the acoustically induced Raman spectra at different temperatures one can conclude that the effect is caused prevailingly by acoustically induced electron-phonon anharmonicity, which is larger in the vicinity of the ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

Photostimulated nonlinear optical effects in synthesized PbO-Ga[sub 2]O[sub 3]-Bi[sub 2]O[sub 3]-CdO (PGBC) glasses doped by Yb[sup 3+], Er[sup 3+], and Dy[sup 3+] rare-earth (RE[sup 3+]) ions were discovered. Temperature-dependent measurements of optical photoinduced second-harmonic generation (PISHG) and two-photon absorption were performed in the infrared (IR) range. CO pulse laser (λ=5.5 µm, energy power density up to 3.8 GW/cm² per pulse) was applied as a source of IR-photoinducing and probing (fundamental) light. Absolute values of the PISHG were more than 22% higher than corresponding values obtained for other glasses: As[sub 2]Te[sub 3]-CaCl[sub 2]-PbCl[sub 2] [1] or Sb[sub 2]Se[sub 3]-BaCl[sub 2]-PbCl[sub 2] [2] type. The investigated PGBC system possesses a shorter time response (about 18 ps), compared with other IR nonlinear optical glasses. We have also established that all nonlinear optical susceptibilities are dependent on the type of RE[sup 3+] ion. A maximal value of the PISHG is achieved for the glasses doped by Yb[sup 3+]. The PISHG values increase significantly below 25 K. We have carried out ab initio molecular dynamics and quantum chemical simulations in order to evaluate the possible contribution of electron-phonon anharmonic interactions in the observed phenomena. We have modeled the influence of the external CO photoinduced beam through the photoinduced anharmonic electron-phonon interactions. A decrease of the delaying time response is achieved. To obtain independent confirmation of the observed dependencies, we have carried out measurements of the ∈[sub 2](E) during the external IR pumping. We have also compared the measured and theoretically calculated dependencies of the IR-induced effects. [ABSTRACT FROM AUTHOR]

We present a band structure approach in connection with a molecular dynamics cluster optimization that accounts for various structural modifications related to the nonstoichiometry of LiNbO[sub 3] crystals. Variation of optical properties with the deviation from the stoichiometric composition can be understood within this approach. The particular role of the electron-phonon contributions to the electro-optic coefficient is shown. Model calculations yield a large dependence of the electro-optic coefficient r[sub 22] on the crystal composition, in agreement with the experimental data. The observed minimum of the r[sub 22] coefficient versus nonstochiometry is explained within a microscopic approach. The r[sub 33] tensor component shows substantially different behavior versus the stoichiometry. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The main spectroscopic properties (absorption, emission, decay times) of Pr[sup 3+]-doped Ca[sub 4]GdO(BO[sub 3])[sub 3] (GdCOB) have been determined for the three X, Y, Z polarizations. The Judd-Ofelt analysis, extended to anisotropic crystals, normalized and modified to take into account the influence of the 4f5d lowest energy level, has been performed and gives reasonable agreement with experimental data. The band energy approach is used for estimations of probabilities of relative cross relaxations and multiphonon relaxation. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Deals with a study of the optical photoinduced second-harmonic generation of SiON films deposited on Si (111) substrates. Experimental details; Theoretical simulation of the photoinduced nonlinear optical effects; Photoinduced kinetics and nonlinear optical susceptibilities; Results and discussion; Conclusions.