| The synthesis of materials for total reflection type of hollow waveguide has been a key point of applications in CO2 laser delivery. In this work the synthesis of sol-gel Al2O3 and GeO2 based films for hollow waveguide delivery of CO2 laser was studied. This research will develop a new route to fabricate materials for hollow waveguide delivery of CO2 laser.In the question of the traditional dip-coating method that is not suitable for the inner coating of capillary and coatings on other irregular surfaces, a drop coating device was particularly designed and equipped. A new method for predicting qualities of sol-gel optical films such as the thickness, compactness and uniformity was proposed.Based on researches of the processes and properties of various alumina sols derived from aluminum iso-propoxide, aluminum nitrate and aluminum sec-butoxide(ASB) through polymerization and peptization technical routes, the alumina sol synthesized from ASB according to peptization route was chosen as the basic sol system for the preparation of alumina reflective films. Using a temperature within 240~260 in stead of 100 as the temperature of temporally heating alumina sol-gel films in multi-time coating can not only eliminate the phenomenon of "zero-growth" in thickness, but also prevent the crack formation and decrease the probability of interfacial pollutions. The surface difference exists in the sol with a mol ratio of ASB/H2O more than 1:100 between the colloidal particle and solvent, combined with the large colloidal particle, small thickness in electrical double layer and lower zeta potential, resulting in its very poor stability in thermodynamics, kinetics and DLVO energy barrier. It was indicted that ethylacetoacetate(EAcAc) can chelated with -Al-OH groups on the surface of the colloidal particles, depressing the activity of the colloidal particles, reducing the interphase distinction between the solid and liquid phase remarkably, lowering the change of Gibbs enthalpy. Therefore, the stable alumina sols with high solidity contents, namely the ratio 1/30 of ASD/H2O can be obtained by introducing EAcAc into the original sol.Sol with higher alumina content with a ratio 1/25 of ASB/H2O can be prepared by adding polyvinylpyrrolidone(PVP) with EAcAc. The stericstabilization of PVP plays an important role to keep the energy barrier above 15kT. The effect of -CH2-CH2-chains and the lateral lactam groups in PVP to retard the condensation of gels, reinforce the gel, and its structural relaxation and its modulus increases with the increase of temperature when the temperature is beyond Tg and PVP acting as an elastomer are all the possible reasons for the anticrack effect of PVP. Compact and homogenous alumina films thicker than 4m can be obtained by using this double modified alumina sol.SiO2-TiO2-GeO2 sol was synthesized from Si(OC2H5)4, Ti(OC4H9)4 and CI3GeCH2CH2COOH. SiO2-TiO2-GeO2 gel glass films were obtained from this sol. The sol derived from (CH3)2Si(OC2H5)2 and Ge(OC2H5)4 was much more stable than that prepared by Si(OC2H5)4 and Ge(OC2H5)4. Compact and smooth sol-gel films thicker than 4m or so can be obtained by using this sol.The phase angle integral of the infrared reflection spectra of materials can be accurately calculated by introduced a infinitesimal parameter A adjacent to the disconnected point and various fitting functions including Polynomial, Gaussian and Lorentzian etc. It was verified that the complex refractive indices at 940 cm-1 for SiO2-TiO2-GeO2, SiO2-GeO2 and A12O3 sol-gel films are 0.53-0.96i, 0.62-0.8 liand 0.69-0.17i, respectively. The total loss an of SiO2-TiO2- GeO2 films coated hollow fiber with diameter of 1000m is 0.69dB/m. The additional loss of SiO2-GeO2 films coated hollow waveguide at 940 cm-1 reaches the magnitude of 10-3 to 10-2 dB/m. As for hollow fibers with diameters of 1000m, 750m and 500m, the total loss an are 0.064dB/m, 0.15dB/m and 0.52dB/m, respectively. The additional loss of A12O3 films coated hollow waveguide at 940 cm is so small that the total loss of hollow fiber is... |
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