Synthesis And Investigation Of Al₂O₃ Based Films For Hollow Waveguide Application In CO₂ Laser Delivery

The study on total-reflective-film hollow-core waveguides is very important for the application of CO₂ laser in many fields such as medical treatment, laser processing and so on.. The synthesis of materials for total reflection type of hollow waveguides has been a key point of applications in CO₂ laser delivery. In this work the synthesis of sol-gel Al₂O₃ based films for hollow waveguide delivery of CO₂ laser was studied by using combining dip-dropping, rising liquid method. We also got the character of alumina sols and the processing for fabricating compact alumina film. At last, We used SJ-CO₂ laser system to test the loss of the hollow fiber.Alumina sols of different content were prepared by using Al(O-Sec-Bu)₃ as precusor, water as solvent, nitric acid as peptizer, ethylacetoacetate(EAcAc) and polyvinylpyrrolidone(PVP) as modified menstruum. We used dip-coating method and spin-coating method prepared of alumina films on the plane glass and used dip-coating method and rising liquid method inside the wall of the fiber. It is indicated that Electrical double layer thickness of Colloidal particles decreases when the nitric acid concentration increases. The zeta potential and total interaction energy of the colloidal particles are both at a maximum when the ratio of nitric acid and H₂O is 0.3:1(mol ratio), and the crystalline phase transformation occurs as y, 8, 9 and α-alumina in turn with the increase of temperature.After we got the high quality of alumina sol which is suitable for coating inside the fiber, the technics were also studied in the fabrication of alumina film by dip-coating method and rising liquid method. It is shown that the decrease of dropping speed and the decrease of coating times help to prepare homogeneous compact films. Compare with coating on plane glass. We must change our heat treatment and last heat temperature to improve the micro-cracks of the film which formed when coating inside the fiber. Using a temperature at 260℃ as the temperature of temporally heating alumina sol-gel films and using 800℃ as the last heat temperature can prevent the crack formation and decrease the probability of interfacial pollutions. When we use rising liquid method to coating film inside the fiber. The resultindicated that the liquid rising speed was not significant influence in the film quality. 4.5(0. m alumina thick films which were dense and smooth were obtained using the alumina content with a ratio 1/80 of ASB/H2O (mol ratio). We get the total loss of this hollow fiber is 4dB/m using SJ—CO2 laser system to test.The general analysis of dip-coating method and rising liquid method shows that alumina thick films which were dense and smooth were obtained by using this two kinds of methods. But the result shows that the quality of the thickness of the films fabricated by the rising liquid methods are higher than dip-coating method and the fiber loss of the films fabricated by the rising liquid methods are smaller than dip-coating method.