Synthesis and characterization of hydrothermally grown zinc oxide (ZnO) nanorods for optical waveguide application

We report a simple method to synthesize Zinc oxide nanorods, grown without using catalysis with less complicity. This was done by hydrothermal treatment of zinc nitrate and hexamine at 90 degrees C and various times (5-20h) and also we find that the nanorod size and shape depends on heating rate, temperature and heating time. ZnO nanorods have been investigated for their light guiding ability and their effective index of refraction for use in near air index optical systems by developing a ridge waveguide structure. ZnO nanorod waveguides (100 mu m w x 2.5 mu m h x 1mm l) were grown on a seeded glass substrate template using hydrothermal process at 90 degrees C. Modification of the substrate surface in order to obtain dense perpendicularly-oriented ordered nanorods induced selective growth. These structures were characterized by SEM, EDX, and XRD. The guiding property, i.e. locally excited photoluminescence propagation along the length of the waveguide, was analyzed with image-processing program in MATLAB. Following application of a fiber optic white light source on the ZnO nanostructure, we found that light propagation occurred within the glass substrate. No such propagation occurred if light was applied on uncoated areas of the glass. Modeling of waveguide behavior to determine the number propagating modes was exercised using waveguide mode solver in COMSOL.