Visibly transparent near-UV dye (Exalite 377E)-doped silica in the form of parallelepiped were prepared by the low-temperature sol-gel process. The laser output performance of dye-doped sol-gel silica samples pumped by a short pulse (1 ns) N2 laser at 337 nm was reported. With a grating as the wavelength selection element, the laser was tuned from 367 to 387 nm with a laser linewidth of 2 nm. Using a resonator cavity consisting of two flat mirrors, the sol-gel laser showed a slope efficiency of 34.7% and a pump energy threshold of 20 μJ. The variation of sol-gel laser energy output as a function of the number of pulses under repetitive N2 laser excitation was investigated. The laser output energy decreased initially with the number of shots. The output energy recovered to its original intensity after a ten minute interruption in pumping. In this way, the dye-doped samples showed no signs of long term degradation after being irradiated at 337 nm for tens of thousand shots.
Doped and undoped silica slabs were fabricated through the use of the sol-gel technique. Extended UV transmission was observed for HCl-catalyzed sol-gel silica. Under transverse pumping with a XeCl laser, narrow-linewidth 1,0.9-nm2 laser oscillation from silica slabs doped with coumarin 460 1C4602 was achieved in a grating-resonator cavity configured in the grazing-indicence geometry. Tuning of the C460-doped silica laser extended from 468 to 494 nm. The conversion efficiency of the narrow-linewidth blue laser was 5.5%.Dye-doped inorganic matrixes derived through the sol-gel route-a new glass-making technologyconstitute a new class of tunable solid-state laser materials that offer tuning capabilities ranging from the UV to the near infrared. Previously, polymeric materials such as poly1methylmethacrylate2 1PMMA2 and modified PMMA 1MPMMA2 have been used with some success as host materials for organic dyes. Because of the low temperatures that are employed during the sol-gel process, organic dopants, which will otherwise be destroyed in conventional glassforming processes, can be introduced into sol-gel glasses to serve as optically active centers. In view of the many potentials of dye-doped sol-gel-derived glasses, research interest regarding this class of tunable solid-state-laser materials has been considerable. Rhodamine-and coumarin-doped silicates have been characterized spectroscopically and the mechanical properties ascertained. 1,2 Gain measurements, broadband lasing, and frequency tuning have been performed with a liquid-dye laser or a frequencydoubled YAG laser as the pump source. [3][4][5] Our group has studied XeF-laser-induced emission properties of 10 dyes in a sol-gel silica matrix that covers the spectral range from 400 to 800 nm. 6,7 Most of the recent studies on dye-doped sol-gel lasers has been with the green-to-red spectral regions because pumping can be provided conventiently with frequency-doubled Nd:YAG lasers at 532 nm. 8 Recently, Ferrer et al. 9 also reported having lased dye-doped PMMA in the blue-green range. Applications in fields like optical storage, underwater communication, etc., however, call for efficient tunable lasers in the blue. Excimer lasers in the UV are powerful pump sources for liquid-dye lasers. 10 They are in fact most useful when one pumps dyes in the blueto-UV spectral regions. Silica glass formed by means of the sol-gel route, however, usually transmits poorly in the UV. Porous sol-gel silica glass supplied by a commercial vendor 1Geltech, Alachua, Fla.2, for instance, has UV cutoffs that vary from 300 to 500 nm, depending on the pore sizes. Hence, excimer-laser pumping of dye-doped sol-gel glass that exhibits poor UV transmission could lead to a shortened of laser lifetime and eventually to the destruction of the sample. When HCl was used as the catalyst during the sol-gel process, UV transmission of the undoped sol-gel silica was found to extend down to 260 nm, which thus permitted safe XeCl-laser pumping at 308 nm. 11 Wideband tuning of silica slabs that were do...
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