색소가 첨가된 졸-겔 실리카 봉의 광학적 특성
Optical properties of dye doped sol-gel silica rods
물리학과 광 및 플라스마전공
Sol-Gel법 실리카봉 광안정성;
- 원문 URL
The sol-gel method is known to be a low temperature process and useful synthesis technology for preparing novel luminescent materials and optical device fabrication[1-5]. In the last years, extensive research has been performed to obtain sol-gel glasses for optical applications[6-7]. The sol-gel glasses doped with organic molecules have high efficiency of luminescence and the saturable absorption properties. A number of organic dye molecules have been successfully incorporated into silica matrices by the sol-gel process. The majority of such studies have been focused on a slab and film form. There have been far fewer reports of dye-doped sol-gel silica rods. Dye(Coumarin 6H, Coumarin 314, Coumarin 337, Rhodamine 110, Rhodamine 6G) doped sol-gel silica rods were prepared by hydrolysis and polycondensation of tetraethosysilane(TEOS), with formamide as a drying control chemical additive(DCCA). The fluorescence characteristics of dye doped sol-gel silica rods and Coumarin 314 in SiO_(2)-GPTMS were studied by using a linear Xenon flashlamp. Fluorescence spectra were obtained for all the dye-doped sample studies and compared with dye solution in ethanol. A persistent red-shifting in the sol-gel silica spectra was observed. Solvatochromic and local environmental effect were invoked to explain the red-shifting. The photostability of the dye doped sample under UV lamp(or flashlamp) was proposed with fluorescence and absorbance spectra measurement. The modification of GPTMS on SiO_(2) matrix delays the photo-decay of dye doped sample, due to the refinement of hybrid microstructure through influencing the hydrolysis and condensation process. The bridge between organic chains and SiO_(2) network can become the channel of relaxing the absorbed energy, therefore preventing bond-breaking caused by energy aggregation. The normalized fluorescence energy of the rod was measured against number of shots at a fixed flashlamp pump energy. The photostability of the dye doped sample was very high. The fluorescence energy of the rods is restored to its initial value when we restarted the pump radiation in ten minutes after stopping it. During the experiment, no sign of long-term degration showed in all samples after the photostability measurement. We believe that the drop in fluorescence energy as the number of shots accumulated was mainly due to the slow waste heat. The status of dye bonding to the inorganic matrix can be inferred extracted from dye quantities. The absorption of dye doped sample is measured as a function of the soak time in water. The Rhodamine 6G sol-gel sample did not show any decline in the absorbance after near by 3000 min. This indicate that the dye is bonded to the SiO_(2) matrix. In contrast, the Coumarin 314 sol-gel sample showed a decrease in absorption of more than 80% within 2000 min of soaking, indicating substantial dye loss. Dye extraction of Coumarin 314 doped SiO_(2)-GPTMS sample are much small than sol-gel sample. Extraction results indicate that under proper processing condition, dye moleculescan be incorporated within a SiO_(2)-GPTMS matrix to provide a more chemically stable material than a sol-gel matrix. The bulk transmission losses can seriously inhibit or even prevent laser action under flashlamp pumping. The bulk transmission losses of dye-doped sol-gel silica rods should be reduced to a minimum in order that the losses do not excess the available gain under flashlamp excitation. To obtain good laser efficiency, the bulk losses smaller than 0.5 %/cm are required. The bulk transmission losses of the rods immersed in water were measured to be 0.51-0.57 %/cm and the bulk transmission losses of the rods not immersed in water were measured to be 4.99-5.61 %/cm. it arises from somewhat similar values of refractive index of silica gel glass and water, 1.40 and 1.33 respectively. The mixed dye method has received considerable attention because it is promising method to improve the efficiency of dye lasers and broaden the laser emission spectrum. In a dye mixed solution, the excitation energy can be efficiently transferred from the donor to the acceptor. Most of the studies conducted so far report investigation of energy transfer between dyes in liquid media. To our knowledge, no work has been reported on the energy transfer of Rh6G : C337 dye mixture in the sol-gel silica matrix. The present investigations of the energy transfer between Coumarin 337(donor) and Rhodamine 6G(acceptor) showed that the fluorescence intensity increases with the donor concentrations up to the critical concentration (5×10^(-7)M). In addition, a significant enhancement of the fluorescence intensity was observed. Moreover, when the Coumarin 337 molecules are added to the Rhodamine 6G dye, the efficiency of the mixed dye samples in a sol-gel silica matrix increases considerably and the maximum efficiency is obtained at the donor concentration of 5×10^(-7)M.