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51.
K. Petermann 《Optical and Quantum Electronics》1990,22(Z1):S199-S218
The lasing properties of tunable solid state lasers can be strongly influenced by Excited State Absorption (ESA). It is shown that the tuning behaviour of Cr:GSGG and Cr:LLGG is limited at short wavelengths due to the ESA transitions2E 2T2 (b),2T1 (b) and4T2 4T1 (b), respectively. At long wavelengths the4T2 4T1 (a) ESA transition narrows the tuning range largely. The reason is that both levels are Jahn-Teller split due to the centric chromium site resulting in a very broad ESA band. In Ti: YAIO3 strong ESA of the pumping wavelength into a charge transfer band occurs, which is caused by a Ti3+/Fe3+ complex centre. By this transition the pumping efficiency is diminished largely. It is believed that the lasing behaviour of Ti: YAIO3 can be improved considerably by growing of highest iron-free crystals. 相似文献
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H. Stange K. Petermann G. Huber E. W. Duczynski 《Applied physics. B, Lasers and optics》1989,49(3):269-273
We report on room-temperature cw laser action of Er3+: Yttrium-aluminum-garnet (YAG) and Er3+: Yttrium-gallium-garnet (YGG) crystals at 1.64 m. The laser operates from the metastable4
I
13/2 manifold into an upper Stark level of the4
I
15/2 ground-state manifold of Er3+. Due to reabsorption losses, the Er3+ concentration of the laser crystals must be low. Laser pumping at a wavelength of 647.1 nm yields lowest thresholds around 30 mW and slope efficiencies up to 12.7% for Er:YAG. Laser operation in Er:YGG is achieved with higher thresholds of about 200 mW and smaller slope efficiencies of 0.9%. The effective emission cross section in YAG is estimated to be e5×10–21 cm2.Dedicated to Prof. Dr. Herbert Welling on the occasion of his 60th birthday 相似文献
54.
Pure-silica optical waveguides, fiber couplers, and high-aspect ratio submicrometer channels for electrokinetic separation devices 总被引:1,自引:0,他引:1
Mogensen KB Eriksson F Gustafsson O Nikolajsen RP Kutter JP 《Electrophoresis》2004,25(21-22):3788-3795
A new fabrication procedure for integration of ultraviolet transparent pure-silica planar waveguides, fiber couplers and high-aspect ratio submicrometer channels is presented. Only a single photolithographic mask step is required. The channels are 80-90 microm deep and the width can be reduced to about 0.5 microm, corresponding to a height-to-width ratio of more than 150. The core of the waveguides consists of pure silicon dioxide, which is favorable over doped silica, due to the absence of absorption centers associated with the dopants. This furthermore improves the long-term stability of the waveguides, because of an increased radiation resistance of the glass. The propagation loss decreases from 1.0 dB/cm at 200 nm to 0.2 dB/cm at 800 nm, which, to our knowledge, is the lowest propagation loss reported for integrated planar waveguides in the ultraviolet wavelength region to date. The effective optical path length is 1.2 mm for an absorbance cell with a nominal length of 1.0 mm, indicating effective suppression of stray light. The limit of detection for paracetamol when present in the entire channel network was determined to 3 microg/mL. Finally, the applicability of the fabricated devices for capillary electrophoresis was evaluated by separation of caffein, paracetamol and ketoprofone using absorbance detection at 254 nm. 相似文献
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Klaus Weisskopf 《Journal of polymer science. Part A, Polymer chemistry》1988,26(7):1919-1935
The use of the solvent mixture chloroform/hexafluoroisopropanol (98 : 2 vol %) in the GPC-analysis of polyethylene terephthalate (PET) is described. PET-samples of different molecular weight have been prepared and characterized by light scattering, viscometry, and improved techniques of osmometry and end group titration. These well characterized samples were used in calibrating the GPC. The calibration with polydisperse standards was found superior to the universal calibration procedure in the solvent system chosen. 相似文献