Due to the economic merits based on a simple fabrication process, optical waveguide devices have been actively studied and developed for low cost mass production. UV embossing processes for polymer-based materials are suited to profit mass production of optical waveguide. A special advantage of UV embossing is low temperature and low pressure process compared with other fabrication methods, e.g. hot embossing. And another passive alignments also can be fabricated with the waveguide in one step. However, until now the commercial application of polymer waveguide is limited because of high optical loss and temperature-dependences. Instead of polymers, the organic-inorganic hybrid material has high temperature resistance (until around 300℃) and has low optical loss obtained by non-hydrolytic sol-gel process and also has very low birefringence.
The solution of non-hydrolytic sol-gel method is used to produce thin films of low loss photo-patternable hybrid organic-inorganic polymeric glass on silicon. Because of cooking sol-gel solution without water, there is very low quantity of silanol group (Si-OH), which is a main cause of optical loss, in non-hydrolytic sol-gel hybrid MD material. Glasses consist of photo-initiator, methacryloxyprolpyl-trimethoxysilane (MPTMS), diphenyl silanediol (DPSD) are suitable for fabricating optical components such as ridge waveguides by using UV-based embossing method. The used photo-initiators are 2,2-Dimethoxy-2-phenylacetophenone (Benzildimethylketal : BDK), 2-Benzyl-2-(dimethylamino)-4’-morpholinobutyrophenone (Irg369). These films showed both refractive index and thickness change after selective UV irradiation and drying. Through UV-based embossing method, the patterned films can be used fabricating devices without development process.
The low silanol(Si-OH) group contained MD material’molecular structures were investigated by $^29Si$ NMR and FT-IR spectroscopy and UV-spectrophotometer. Non-hydrolytic sol-gel hybrid material shows very low birefringence and thermo-optic coefficient as well. The thickness and refractive index of various photoinitiator doped sol-gel hybrid glass films were measured by using prism coupler. During photo-polymerization, optical character is changed with varying photo-initiator quantities. Through using the photo-DSC (differential scanning calorimetry), photo-polymerization of non-hydrolytic hybrid material is investigated with varying photo-initiator quantities. Finally, optical loss of MD material is measured by prism coupling method and cutback method.
