ABSTRACT
High-quality monoclinic planar waveguide crystals of Tm-doped KY(WO(4))(2) were grown by liquid-phase epitaxy with several dopant concentrations and thicknesses. Waveguide lasing in the 2 mum spectral range was demonstrated in the fundamental mode. The maximum continuous-wave output power achieved was 32 mW using a Ti:sapphire laser pump near 800 nm.
ABSTRACT
We demonstrate passive mode locking based on the novel monoclinic double tungstate crystal Yb:KLu(WO4)2. We report the shortest pulses ever produced with an Yb-doped tungstate laser using a semiconductor saturable absorber. A pulse duration of 81 fs has been achieved for an average power of 70 mW at 1046 nm. We compare the performance of the polarization oriented parallel to the Nm- and Np-crystallo-optic axes. Results in the femtosecond and picosecond regime are presented applying either Ti:sapphire or diode laser pumping. The great potential of Yb:KLu(WO4)2 as an active medium for ultrashort pulses is demonstrated for the first time, to our knowledge.
ABSTRACT
A new series of iridium(III) mixed ligand complexes TBA[Ir(ppy)(2)(CN)(2)] (1), TBA[Ir(ppy)(2)(NCS)(2)] (2), TBA[Ir(ppy)(2)(NCO)(2)] (3), and [Ir(ppy)(2)(acac)] (4) (ppy = 2-phenylpyridine; acac = acetoylacetonate, TBA = tetrabutylammonium cation) have been developed and fully characterized by UV-vis, emission, IR, NMR, and cyclic voltammetric studies. The lowest energy MLCT transitions are tuned from 463 to 494 nm by tuning the energy of the HOMO levels. These complexes show emission maxima in the blue, green, and yellow region of the visible spectrum and exhibit unprecedented phosphorescence quantum yields, 97 +/- 3% with an excited-state lifetimes of 1-3 micros in dichloromethane solution at 298 K. The near-unity quantum yields of these complexes are related to an increased energy gap between the triplet emitting state and the deactivating e(g) level that have been achieved by meticulous selection of ligands having strong ligand field strength. Organic light-emitting devices were fabricated using the complex 4 doped into a purified 4,4'-bis(carbazol-9-yl)biphenyl host exhibiting a maximum of the external quantum efficiencies of 13.2% and a power efficiency of 37 lm/W for the 9 mol % doped system.
