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D. Schneider S. Hartmann T. Benstem T. Dobbertin D. Heithecker D. Metzdorf E. Becker T. Riedl H.-H. Johannes W. Kowalsky T. Weimann J. Wang P. Hinze 《Applied physics. B, Lasers and optics》2003,77(4):399-402
We report on a wavelength-tunable organic solid-state laser based on a second-order distributed-feedback (DFB) resonator design with the guest–host system Alq3:DCM2 as the gain medium. The laser wavelength can be shifted from 608.9 to 646.5 nm by varying the grating period of the Bragg reflector. This allows the characterization of laser parameters for a large wavelength region on a single sample. The laser threshold and output characteristics are measured for different laser wavelengths. A minimum threshold for laser activity occurs at a lasing wavelength of 633 nm, giving the spectral position of the gain maximum. PACS 42.70.Jk; 78.45.+h; 78.66.Qn 相似文献
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Adler F. Burkard M. Schweizer H. Binder E. Hallstein S. Klein W. Trnkle G. Weimann G. 《Il Nuovo Cimento D》1995,17(11):1333-1337
Il Nuovo Cimento D - The cooling of photoexcited hot carriers in 2D, 1D and 0D systems is studied experimentally. In comparison with a theoretical carrier relaxation model which holds for 2D and 1D... 相似文献
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A laser induced etch process is described which uses a pulsed 248 nm KrF excimer laser and Cl2 atmosphere for the fabrication of monolithic continuously curved reliefs in InP substrate. In a bakeable processing chamber with low base pressure a wide range of laser fluences is available for damage-free etching. Especially, by photothermal heating far above the melting point, mirrorlike smooth surfaces are obtained. The etch rate characteristics are correlated to the maximum surface temperature reached during the laser pulse. The etch rate is independent of pressure and gas flux in the ranges 0.1–10 mbar and 20–300 sccm, respectively. It increases, however, with the background substrate temperature. Etch rates of up to 3.6 nm/pulse or 4.3 lm/min are possible at 20 Hz pulse repetition rate without visible surface damage. The process exhibits a smooth increase of the etch rate from 1 to 3 nm/pulse between 200 and 300 mJ/cm2, which could be used for making curved reliefs by optical transmission variations on the projection mask. 相似文献
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Mark D. Gehlsen Peter A. Weimann Frank S. Bates Steven Harville Jimmy W. Mays George D. Wignall 《Journal of Polymer Science.Polymer Physics》1995,33(10):1527-1536
Six nearly monodisperse substituted poly(styrene) homopolymers, poly(styrene) (PS), poly(2-methylstyrene) (P2MS), poly(3-methylstyrene) (P3MS), poly(4-methylstyrene) (P4MS), poly(tertiary-butylstyrene) (PtBS), and poly(α-methylstyrene) (FαMS) were anionically polymerized and subsequently saturated using heterogeneous hydrogenation techniques to poly(vinylcyclohexane) (PVCH), poly(2-methylvinylcyclohexane) (P2MVCH), poly(3-methylvinylcyclohexane) (P3MVCH), poly(4-methylvinylcyclohexane) (P4MVCH), and poly(tertiary-butylvinylcyclohexane) (PtBVCH), respectively. In each case, except PαMS, the materials were saturated to > 99% conversion with no chain degradation. PS hydrogenations required the addition of small amounts of tetrahydrofuran to the reaction solvent cyclohexane to enhance miscibility and eliminate large-scale chain degradation. Density gradient and differential scanning calorimetry (DSC) measurements were used to characterize the density and glass transition temperature, Tg, of the unsaturated and saturated polymers. Saturation reduces the density by 3% to 11% and changes Tg substantially. The greatest variation in Tg is obtained with the 3-methyl substituted species where a 63°C increase is observed, while the highest measured Tg is 186°C for P2MVCH. Small-angle neutron scattering (SANS) experiments on binary mixtures of hydrogenous and deuterium labeled PVCH derivatives provided a determination of bulk chain statistics. The statistical segment length is relatively insensitive to vinylcyclohexane ring substitution, except with P3MVCH where a 20% greater value is obtained. ©1995 John Wiley & Sons, Inc. 相似文献
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Dimethyl(tetramethylcyclopentadienyl)silyl-, -germyl-, and -stannylphosphanes. X-Ray Structures of Chloro(dimethyl)tetramethylcyclopentadienyl-stannane and Tetracarbonyl[1-dimethyl(tetramethylcyclopentadienyl)germyl-3,4-dimethyl-phospholene]iron(0) Me2Cp′SiCl ( 1 ) (Cp′ = C5HMe4) reacts with magnesium and R2PCl (R = Ph, tBu) as well as PCl3 in tetrahydrofurane yielding Me2Cp′SiPPh2 ( 4 ), Me2Cp′SiPtBu2 ( 5 ) and (Me2Cp′Si)3P ( 6 ) respectively. The reaction of Me3SiPPh2 ( 7 ) or Me3SiPC4H4Me2 ( 10 ) with Me2Cp′GeCl ( 2 ) and Me2Cp′SnCl ( 3 ) leads to the formation of Me2Cp′EPPh2 (E = Ge ( 8 ), Sn ( 9 )) and Me2Cp′EPC4H4Me2 (E = Ge ( 11 ), Sn ( 12 )). 11 reacts with Fe(CO)5 with formation of Fe(CO)4[(PC4H4Me2)GeCp′Me2] ( 13 ). 3 crystallizes in the space group P21/n with a = 986,7(1), b = 1247,3(2), c = 1028,2(1) pm, β = 92,71(1)°, Z = 4 and V = 1264,1(2) 10?30 m3. The final refinement resulted in R1 = 0,0249 for 2097 observed reflexions with Fo ≥ 4σ(Fo). 13 crystallizes in the space group P21/n with a = 967,7(3), b = 1298,70(16), c = 1832,7(3) pm, β = 95,810(19)°, Z = 4 and V = 2291,4(8) 10?30 m3 (R1 = 0,0444 for 4043 observed reflexions with Fo ≥ 4σ(Fo). 13 forms a trigonal bipyramide with the phosphane ligand 11 in an axial position. 相似文献
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