Tadeusz Lukasiewicz

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.

Effect of temperature on excitation energy transfer and upconversion phenomena in Er:YVO4 single crystals

Abstract Investigation of excitation and decay of Er 3+ in YVO 4 single crystals has been carried out at temperature range from 5 to 500 K. In the limit of low Er 3+ content, the temperature dependence of the 4 S 3/2 decay is not consistent with predictions of multiphonon relaxation model. In heavily doped crystals the 4 S 3/2 decay is governed by cross relaxation process, whose rate grows steadily with increasing temperature. An efficient upconverted luminescence near 550 nm following a cw and short pulse (5 ns) excitation of the 4 I 9/2 level in the system under study has been recorded and analysed. Contribution of the excited state absorption to these phenomena has been considered.

Growth and Characterization of LiNbO3 Single Crystals Doped with Cu and Fe Ions

Single crystals of lithium niobate doped with 0.03 and 0.1 at.% of Cu or Fe ions were grown by the Czochralski technique. Optical absorption spectra in visible and infrared regions before and after • irradiation with doses up to 10 5 Gy were measured and positions of both dopants in LiNbO 3 lattice were analyzed according to changes in optical absorption in the range of OH group absorption. Some properties of crystals doped with Cu during the growth processes were compared to those for specimens doped by thermodiffusion. It was observed that doping with Cu results in an increase of crystal resistance to radiation.

Radiation Defects in Oxide Compounds

Yttrium-aluminum garnets, strontium and barium lanthanum gallates, lithium niobate and tantalate as-grown crystals and doped by diffusion with rare-earth (Nd, Dy, Er, Tm, Ho, Pr, Ce) and metal transition elements (Mn, Cr) were investigated optically and using Electron Spin Resonance method before and after gamma, electron and proton irradiation.

Optical transitions of Pr3+ ions in Ca4GdO(BO3)3 crystals

Abstract Optical properties of Pr 3+ ions in gadolinium calcium oxoborate Ca 4 GdO(BO 3 ) 3 (GdCOB) nonlinear crystals have been studied. Polarized absorption and emission spectra and fluorescence lifetime measurements have been performed and discussed using modified Judd-Ofelt theory. The system is characterized by intense red emission at 610 nm corresponding to the 1 D 2 → 3 H 4 transition, no emission from the excited 3 P 0 state has been observed. 1 D 2 emission has been investigated under pulsed excitation and the experimental lifetimes for this level has been compared with this obtained theoretically by using Judd–Ofelt approach.

Effect of ionizing radiation on optical and lasing properties of Y3Al5O12 single crystals doped with Nd, Er, Ho, Tm, Cr ions

Abstract The influence of gamma irradiation on optical and lasing properties of YAG:Er, YAG:CTH, YAG:Nd and YAG:Cr4+ single crystals were studied. For no thermal annealed rods from YAG:Er and YAG:CTH crystals the increase of laser output energy was established. The mechanisms of radiation sensibilization are discussed.

Electron spin resonance and optical measurements of yttrium ortho-vanadate, doped with Nd3+ ions

Abstract The electron spin resonance and optical properties of YVO 4 and YVO 4 :Nd 3+ crystals before and after ionizing radiation treatment with gamma quanta and electrons are presented. The obtained YVO 4 and YVO 4 :Nd 3+ (1 at. % Nd) single crystals show a lower content of point defects (growth defects, e.g. oxygen vacancies) and consequently, lower susceptibility to ionizing radiation in comparison to YAG: Nd 3+ crystals. Because of the angular dependence of the Nd 3+ resonance line position, we suppose the presence of structural defects like twins and mosaic structure. Moreover, for the first time the ESR spectrum of V 4+ in YVO 4 is reported.

Radio- and VUV - Excited Luminescence of YAP:Ce, YAP:Pr and YAG:Pr

In this communication we report initial results of studies on x-ray and VUV excited luminescence of YAP and YAG crystals activated with Pr3+ and YAP activated with Ce3+. Excitation and luminescence spectra of Pr3+ and Ce3+ d-f and Pr3+ f-f emissions and luminescence time profiles under pulsed synchrotron excitation are presented and analyzed in order to identify and characterize various host-to-ion energy transfer channels. The results support the notion that direct and trap mediated capture and recombination of holes and electrons via Pr3+ or Ce3+ ions provide the dominant mechanism of radio luminescence production in both YAP and YAG crystals.

Spectroscopic properties of holmium doped crystals

The spectroscopic properties of ions in crystals have been investigated using optical absorption, luminescence and lifetime measurements in the 5-300 K temperature range. The low temperature, polarized absorption spectra of in this matrix have allowed us to identify the Stark levels of the different multiplets up to 30 000 . The results are consistent with symmetry for the rare-earth ions and a singlet A character for the lowest Stark level of the ground state. Several transitions show additional structure which indicates multi-site occupancy for the ions. The measured oscillator strengths of the transitions between the J manifolds at 300 K are compared with those derived from the Judd-Ofelt theory. The radiative transition rates and radiative lifetimes have been calculated. The luminescence observed at 5 K has been attributed to (18 100 ), (15 060 ) and (13 150 ) transitions. The obtained data are used to discuss the radiative properties for luminescent levels of ions in the matrix. The emission cross-section of a potential laser line at 2 m connected with the transition is estimated.

Spectroscopic and laser properties of resonantly (in-band) pumped Er:YVO 4 and Er:GdVO 4 crystals: a comparative study

We compared spectroscopic properties and resonantly (in-band) pumped laser performances of Er3+:YVO4 and Er3+:GdVO4 single crystals, at room and cryogenic temperatures. It was shown that these gain materials are very similar in absorption and emission spectra, associated with transitions between 4I15/2 and 4I13/2 manifolds of Er3+ ions. Both lasers demonstrated comparable performances in quasi continuous wave (QCW) operation at both temperatures. However, Er3+:GdVO4 material performed better in a continuous wave (CW) mode, under the higher thermal load.