Student Project Abstracts 2005 - Pluto - University of Washington

FATHALIPOURFigure 5. Fluorinated sol-gel birefringenceFigure 7. Birefringence of Hydrogen based filmWhen the hydrogen based sol-gels were analyzed the plotsshow a low amount of dispersion in both TE and TM direction.The data shown is for the spin speed of 1500/30 rps, which demonstratesthe low dispersion that all the hydrogen based sol-gelsexhibit as seen in Figure 6.Figure 6. TE dispersion curveHowever, the birefringence for these samples was exceptionallyhigh compared to the SiO2 and fluorinated samples. Lookingat the scale it can be seen that the magnitude of the birefringencefor the hydrogen based sol-gel is ten times larger than that ofthe SiO2 and fluorinated films that is why it is such an interestingresult. This high birefringence that these samples exhibitedis demonstrated in Figure 7. High birefringence can lead to localvariations in the refractive index that can subsequently resultin scattering. It is hypothesized that the high birefringence ofthe hydrogen-based sol-gels could be a major contributor to theanomalously high waveguide loss that has been observed in thesefilms.CONCLUSIONSThe hydrogen based sol-gel samples had the largest birefringencethis finding is important because it means that there is alarge change in index depending if its TE or TM. The large differencemeans that the sol-gel is polarization dependent, whichcould have a large impact in optical systems. The large birefringencealso means that there is potentially birefringence inducedwaveguide loss in the hydrogen-based sol-gels. The loss is due tothe microdomain scattering that happens within the waveguides.FUTURE WORKIn future research poled and un-poled films will also belooked at, the main focus will be on poled films and how the indexof refraction varies across the film, as poling nonuniformitiescan lead to significant problems in fabricating high performancedevices. Nanoparticle doped sol-gels will also be investigatedin future research. The data will then be used to investigate newor improved cladding materials for a target core material. A keygoal of this next phase will be to develop a cladding material witha refractive index much closer to that of the electro-optic polymermaterial, which has a refractive index of approximately 1.62 at1550mn. Two potential approaches are considered. One is highindex nanoparticle doping of sol-gels; silicon nanoparticles withindices of 3.5 have been obtained and will be dispersed in photopatternablesol-gels that have been previously developed. Thedependence of the refractive index on nanoparticle loading willbe studied, assuming that good dispersions can be made. Anotherapproach is to investigate the use of selective photobleaching ofthe electro-optic polymer layer to alter the refractive index, thereforeallowing it to be a cladding layer for itself.CMDITR Review of Undergraduate Research Vol. 2 No. 1 Summer 2005 47