Fabrication and measurements of sol-gel planar and stripe waveguides in LTCC structure

The sol-gel technique has been long used for the purpose of integrated optics and connected with the Low Temperature Co-fired Ceramic technology seems to be a very promising solution to the integrated optics issue. Versatile SiO₂ sol-gel silica and hybrid SiO₂-TiO₂ sol-gel layers have been fabricated and deposited on substrate in the dip-coating process. In order to measure the layers an ellipsometer has been used. A wide range of achieved refractive indexes and thicknesses enabled to produce a planar waveguide on a LTCC substrate. The structure has been investigated using the prism coupler technique which confirmed its waveguide character. In order to fabricate a stripe waveguide in a LTCC channel structure both SiO₂ and hybrid SiO₂-TiO₂ sol-gel glass have been used. The LTCC substrate was dip-coated with pure silica - as the waveguide substrate layer - while the channel was filled with the hybrid solution which performed higher refractive index than silica. The structure 140 mum high and 500 mum wide has been measured with the help of cut-off technique and its attenuation has turned out to be 2,46 dB/cm at the wavelength of 632,8 nm.