The width of spiral-patterned zinc oxide (ZnO) nanorod coatings on plastic optical fiber (POF) was optimized theoretically for light-side coupling and found to be 5 mm. Structured ZnO nanorods were grown on large core POFs for the purpose of alcohol vapor sensing. The aim of the spiral patterns was to enhance signal transmission by reduction of the effective ZnO growth area, thereby minimizing light leakage due to backscattering. The sensing mechanism utilized changes in the output signal due to adsorption of methanol, ethanol, and isopropanol vapors. Three spectral bands consisting of red (620 to 750 nm), green (495 to 570 nm), and blue (450 to 495 nm) were applied in measurements. The range of relative intensity modulation (RIM) was determined to be for concentrations between 25 to 300 ppm. Methanol presented the strongest response compared to ethanol and isopropanol in all three spectral channels. With regard to alcohol detection RIM by spectral band, the green channel demonstrated the highest RIM values followed by the blue and red channels, respectively.
This paper deals with mathematical modeling and study of nonlinear switching in optical fiber Bragg gratings (FBG) by a transfer matrix method. Critical parameters contributing to high performance nonlinear fiber Bragg grating were studied. The transmission spectrum centered at 1550 nm was analyzed with varying number of layers and refractiveindices. The study showed that by proper modification in grating length of the FBG, we were able to optimize transmission spectrum for required application. The nonlinear behavior of FBGs can be further applied in optical switching applications (all-optical logic gates).
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°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 μm w x 2.5 μm h x 1mm l) were grown on a seeded glass substrate template using hydrothermal process at 90°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 imageprocessing 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.
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