Irena Sokolska

Spectroscopy of crystals

The polarized absorption spectra, time-resolved emission spectra, and emission lifetimes of doped crystals were measured. An intense emission from the level was observed. The positions of the levels, experimental oscillator strengths, and branching ratios from the and levels were determined. The results are discussed in terms of the Judd - Ofelt parameters.

Photon cascade emission in Pr3 + -doped fluorides

An overview about Pr 3+ -doped fluorides exhibiting photon cascade emission is given. The materials investigated, i.e. Pr 3+ -doped YF3, LuF3, PrF3, BaMgF4, LiCaAlF6, LiSrAlF6 and KMgF3, exhibit quantum cutting under vacuum ultraviolet (VUV) synchrotron excitation at wavelengths below 200 nm with a theoretical, internal quantum efficiency higher than one. This quantum efficiency was calculated with the Judd–Ofelt model, which allows the determination of the transition branching ratios. In the emission spectra bands due to the intraconfigurational 4f 2 -4f 2 transitions originating from the 1 S0 and 3 P0 multiplets of the Pr 3+ -ion have been identified. In the excitation spectra in the ultraviolet/VUV spectral range, weak lines due to the 1 S0 as well as broad bands due to the interconfigurational 4f 2

Spectroscopy of LiTaO3:Tm3+ crystals

Abstract The LiTaO 3 :Tm 3+ single crystals with different Tm 3+ concentration were grown by the Czochralski method and their optical properties are presented. The energy levels of Tm 3+ multiplets split in the crystal field are determined. The effect of the thulium concentration and of the temperature on the 3 H 4 emission lifetime is presented. The results of the Judd–Ofelt analysis are presented and discussed.

Anisotropy of optical properties of SrLaAlO4 and SrLaAlO4:Nd

Abstract Single crystals of SrLaAlO 4 and SrLaAlO 4 :Nd have been grown by the Czochralski method and their optical properties have been studied in polarized light. The crystals are positive uniaxial, and their birefringence is stable with respect to temperature in the 290 K–520 K temperature region. Undoped crystal is transparent from 240 nm to 7.6 μm. Intensities of absorption and spontaneous emission of Nd 3+ are slightly lower for light polarized perpendicular than those for light polarized parallel to the optical axis. Laser action in SrLaAlO 4 :Nd has been obtained for the first time using a diode laser as a pump. Stimulated emission occurs in the 1073 nm-1080 nm spectral region. Poor laser performance is attributed to the self-quenching of Nd emission.

Investigation of LiXO3 (X=Nb, Ta) crystals doped with luminescent ions: Recent results

Abstract Processes of transfer of excitation from levels populated by diode laser pumping to upper laser levels in LiTaO 3 :Tm and LiTaO 3 :Ho are considered. Stimulated emission cross section for the 3 F 4 – 4 H 6 transition of Tm and for the 5 I 7 – 5 I 8 transition of Ho in lithium tantalate have been evaluated. Preliminary data concerning the contribution of radiative transitions and multiphonon relaxation to the decay of excited states of Er, Tm and Ho in LiNbO 3 and LiTaO 3 are compared.

Spectroscopic investigation of Mn2+, Pr3+ codoped KMgF3 under vacuum-ultraviolet excitation

Pr3+:KMgF3, Mn2+:KMgF3 and Pr3+, Mn2+:KMgF3 single crystals were grown by the Czochralski method and spectroscopically investigated in order to evaluate possible energy transfer processes between Pr3+ and Mn2+ after vacuum-ultraviolet excitation. These processes are of importance for the possible use of these materials as phosphors for discharge lamps based on the xenon discharge excitation. In Pr3+:KMgF3 besides the already known cascade emitting Pr3+ centre (, ) (Sok?lska and K?ck 2001 Chem. Phys.?270 355), a second Pr3+ centre was clearly observed with 4f5d energy levels shifted to energies below the 1S0 level. For Mn2+:KMgF3 a broad emission band typical for Mn2+ with a maximum at 600?nm and the expected Mn2+ excitation bands in the visible () and vacuum ultraviolet () are observed. In the Pr,Mn:KMgF3 sample investigated, the expected energy transfer process could not be observed within the detection limit of the experimental setup. The efficiency for this energy transfer process was also calculated assuming dipole?dipole interaction and found to be <5% for the sample investigated. The low concentration of the dopant ions and the small oscillator strength of the transition of the Mn2+ acceptor ion is responsible for this low transfer efficiency.

Upconversion-induced blue, green and red emission in Ho3+:BaY2F8

Abstract An analysis of infrared to visible upconversion in Ho3+:BaY2F8 is given. Excitation at 888 nm into the 5 I 8 → 5 I 5 transition leads to intense visible emission in the blue, green and red spectral range. Based on the energy levels of Ho3+ in BaY2F8, and the pump intensity dependencies of the observed emissions, an excitation scheme is presented.

Growth and spectroscopic properties of LiNbO3 single crystals doped with Nd3+ and Yb3+ ions

The LiNbO 3 crystals doubly doped with Nd 3 + and Yb 3 + ions were pulled by the Czochralski method. The optical homogeneity of the crystals was investigated using the residual birefringence maps. The optical properties of the crystals were investigated. The Nd-Yb energy transfer takes place in this system. The positions of the 4 F 3/2 level of Nd 3 + and of the ground 2 F 7/2 and excited 2 F 5/2 levels of Yb 3+ are determined. The splittings observed in the low temperature emission spectra prove that both Nd 3 + and Yb 3 + occupy more than one site in the crystal host.

Infrared to visible conversion of radiation in some Ho3+-doped oxide and fluoride crystals

Abstract The presence of upconversion processes in some Ho3+ doped oxides and fluorides (YAlO3, LiTaO3, YVO4, BaY2F8, LiYF4, K5LaLi2F10) was investigated under continuous wave excitation within the 740–1000 nm spectral range. In some of the materials investigated, excitation into the 5I4 or/and 5I5 multiplets brings about the relatively strong upconverted green emission due to the 5S2→5I8 transition. The excited state absorption spectra, upconverted emission spectra as well as possible mechanisms of excitation are presented.

The up-conversion processes in Ho3+ doped LiTaO3

Abstract The up-conversion processes in Ho 3+ doped lithium tantalate were investigated under continuous wave excitation into the 5 F 5 , 5 I 4 or 5 I 5 multiplets and with the energy due to the 5 I 6 → 5 S 2 transition, which is not resonant with the ground state absorption. The most intense green emission originating from the 5 S 2 multiplet is observed after excitation into the 5 F 5 and 5 I 4 multiplets. The excited state absorption spectrum, emission spectra, dependencies of emission intensity on the excitation power as well as possible mechanisms of excitation are presented.