Amina Bensalah

Crystal Growth of Fluorides for Optical Applications

Ce-doped and undoped LiCaAlF 6 , LiSrAlF 6 , LiYF 4 , LiLuF 4 and KMgF 3 single crystals were grown by the Czochralski technique under CF 4 atmosphere. The effective distribution coefficients of Ce 3+ in LiCaAlF 6 , LiSrAlF 6 , LiYF 4 and LiLuF 4 were determined to be 0.031, 0.028, 0.116 and 0.054, respectively. Laser output energy of 60 mJ and 27mJ were obtained using the grown Ce:LiCaAlF 6 and Ce:LiLuF 4 single crystals, respectively. Undoped LiCaAlF 6 and KMgF 3 single crystals showed a transmission edge at 112 nm and 115 nm, respectively.

Growth and characterization of BaLiF3 single crystal as a new optical material in the VUV region

Abstract The growth of undoped BaLiF 3 (BLF) single crystals, a candidate for window material in the vacuum-ultraviolet (VUV) region, was carried out in a Czochralski system under CF 4 atmosphere. BLF single crystals 1 inch in diameter were obtained and characterized. The thermal expansion coefficient of the BLF single crystal along the 〈100〉-axis was 3.33×10 −5 K. The distribution of birefringence along the 〈100〉-axis was in the order of 10 −7 . The absorption edge of BLF was determined to be 123 nm, showing high potential as an optical window material in the VUV region.

Growth of Tm, Ho-codoped YLiF4 and LuLiF4 single crystals for eye-safe lasers

Abstract YLiF 4 and LuLiF 4 single crystals codoped with thulium and holmium were successfully grown by the Czochralski Technique. The segregation coefficients of the dopants in these crystals were measured and the influence of the dopants on the lattice parameters was investigated. The distribution of birefringence along the a -axis was in the order of 10 −7 in each crystal. Laser performance of both YLiF 4 and LuLiF 4 codoped with thulium and holmium was compared.

Induced absorption phenomena, thermoluminescence and colour centres in KMgF3, BaLiF3 and LiCaAlF6 complex fluorides

KMgF3, BaLiF3 and LiCaAlF6 (LiCAF) single crystals were grown by the Czochralski method under CF4 atmosphere. X-ray irradiation was used to carry out a comparative study of induced optical absorption phenomena and colour centre creation in the vacuum-ultra-violet (VUV), ultra-violet and visible spectral regions. In the case of LiCAF, the X-ray induced absorption peak at 262 nm can be ascribed to F centre. The integral of the induced absorption spectra is significantly lower in LiCAF with respect to the other studied materials; moreover, LiCAF shows stable VUV transmission characteristics and the most resistant surface toward what is regarded as the damage due to reaction with air atmosphere.

Growth of Ce-doped Colquiriite- and Scheelite-type single crystals for UV laser applications

Abstract Ce-doped Colquiriite- and Scheelite-type fluoride single crystals were grown by the Czochralski technique. The formation of inclusions and cracks accompanying the crystal growth was investigated. The effective distribution coefficients of Ce3+ in LiCaAlF6, LiSrAlF6, LiYF4 and LiLuF4 were determined to be 0.031, 0.028, 0.116 and 0.054, respectively. Ultraviolet pulse generations with an output energy of 60 and 27 mJ were obtained from Ce:LiCaAlF6 and Ce:LiLuF4 lasers.

Color centers in LiCaAlF6 single crystals and their suppression by doping

LiCaAlF6 (LiCAF) single crystals pure and doped with MgF2 and BaF2 were successfully grown by the Czochralski technique. Optical absorption measurements in the UV/Visible spectral regions following x-ray irradiation (radiation induced absorption) were performed in order to investigate the radiation damage of the crystals. The F-center absorption band at 262 nm is the dominating induced absorption feature. The amplitude of the F-absorption band is suppressed by more than a factor of 3 in Mg-doped LiCAF compared to undoped, while for Ba-doped LiCAF, almost no variation is obtained. In Mg-doped crystals the optimum doping concentration is of about 0.2 mol % of MgF2 in the melt.

Improvement in the quality of LiCaAlF6 single crystal as window material

Abstract Three-in. size LiCaAlF 6 (LiCAF) single crystals were successfully grown by the Czochralski method. Both measurements of the transmission spectra in the VUV regions and the X-ray rocking curve analysis showed that the crystallinity of LiCAF single crystal was improved by the annealing. Optical absorption measurements in the UV/VIS spectral regions following X-ray irradiation were performed in order to compare the radiation damage with a lithography-grade CaF 2 crystal.

Luminescence, radiation damage, and color center creation in Eu3+-doped Bi4Ge3O12 fiber single crystals

Doped Bi4Ge3O12 (BGO) fiber single crystals were grown by the micro-pulling-down method with the resistance heating system. Optical absorption measurements before and after x-ray irradiation (induced absorption) were performed in order to investigate the radiation damage of the crystals. The Eu3+-doped BGO has shown higher radiation resistance with respect to the equivalently grown undoped BGO fibers. Radio- and photoluminescence characteristics were obtained to clarify the role of Eu3+ in luminescence and scintillation mechanism. Radioluminescence spectra show the intense and slow (decay time of 1.61 ms) 5D0,1−7Fx(x=0−6) radiative transitions of Eu3+, while the intrinsic BGO emission becomes weaker with respect to the undoped BGO. Photoluminescence decay of the intrinsic BGO emission becomes nonexponential and noticeably faster in Eu-doped samples, which evidences the nonradiative energy transfer from intrinsic emission centers to Eu3+ ions. Thermally stimulated luminescence (TSL) measurements above room...

Growth of LiCaAlF6 single crystals with an extended diameter and their optical characterizations

Abstract LiCaAlF6 (LiCAF) single crystals with an extended diameter were grown by the Czochralski (CZ) technique under CF4 atmosphere. Modifying the growth conditions enabled the growth of LiCAF single crystals with 3- and 4-inch diameters. After considering reflection loss, LiCAF showed transmittance over 95% at 157 nm. A precise measurement of the refractive index showed that the birefringence of LiCAF vanished at around 152 nm. The fabrication of a LiCAF lens was demonstrated.

Luminescence and decay kinetics of Yb2+ in LiCaAlF6 single crystal host

Abstract Single crystals of Yb-doped LiCaAlF 6 were grown by the Czochralski technique under CF 4 atmosphere. Photoluminescence and decay kinetics of Yb 2+ center in the LiCalF 6 single crystal host is described in 4–300 K. Phenomenological two excited-state-level model is introduced to obtain quantitative characteristics of the excited state dynamics of Yb 2+ emission center.