Optical properties of distributed feedback waveguide lasers based on sol-gel glass

Distributed feedback (DFB) waveguide laser based on sol-gel materials have generated much interest because of the versatility of sol-gel technique and the potential applications in integrated optics. In this dissertation, Optical properties of sol-gel waveguides based on zirconia materials with or without dye dopants have been investigated by spectroscopic ellipsometry (SE) in the wavelength range from 300 to 800 nm. Lasing characteristics of asymmetric and symmetric DFB waveguide lasers have also been studied.; Zirconia, zirconia-ORMOSIL and zirconia-titania-ORMOSIL films on silicon and glass substrates were prepared by sol-gel method with the thickness from 0.1 to 10 mum. The dispersion curves rose sharply at shorter wavelengths, as expected of typical shape of a dispersion curve near an electronic interband transition. By varying ORMOSIL ratio and the annealed temperature from room temperature to 500°C, the refractive indices changed from 1.53 to 2.15. The extinction coefficients was in the range from 1 x 10-4 to 1 x 10-3. Furthermore, some degree of inhomogeneity has been found in zirconia films when they were treated at the temperature over 200°C. The addition of ORMOSIL and titania improved the microstructure of the zirconia films, and made possible films as thick as 10 mum.; The complex refractive index of zirconia films doped with rhodamine 6G, rhodamine 640 and oxazine 725 was deduced from SE spectra using classical Lorentz model. The derived absorption spectra agreed well with those measured by spectrophotometer. Unlike the pure zirconia films, the spectra of refractive index for dye-doped films exhibited anomalous dispersion. Moreover, the SE spectra of the layered waveguide structures were analyzed by appropriate models. For the multilayer structure, the volume fraction of titania-silica in the interlayer was found to decrease with the initial thickness of the guiding films.; Highly homogeneous sol-gel zirconia and zirconia-ORMOSIL films doped with rhodamine 6G, rhodamine 640 and oxazine 725 on glass substrates have been used in a distributed feedback configuration to obtain tunable laser emission from yellow to near infrared region. As many as eight pairs of TE/TM waves corresponding to eight propagation modes were simultaneously produced by circularly polarized crossing beams in a R6G-doped zirconia-titania-ORMOSIL waveguide laser of 6.7 mum thickness. Symmetric waveguide laser with guiding film of 0.1 mum was also achieved by using a cover layer of sol-gel titania-silica whose refractive index matches that of the glass substrate. Furthermore, the photostability of the R6G and R640 in different sol-gel hosts were investigated. Compared with titania-silica, zirconia-ORMOSIL and zirconia-titania-ORMOSIL, zirconia seemed ideal as a host matrix for functional organic dopants in view of stable lasing emission and high photostability.