| The interaction of light with fiber and waveguide gratings is studied in this thesis in several different contexts. First, scattering from tilted fiber gratings is analyzed using the volume current method (VCM), which calculates the scattering field as if it was generated by a volume current source. Analytical results are obtained for uniform tilted fiber gratings, and we find that the scattering pattern depends on the vector phase matching condition as well as the polarization overlap between incident and scattering waves. For non-uniform fiber gratings, we find that cross-sectional grating variations affect the azimuthal distribution of the scattering pattern, while longitudinal variations affect the cone angle distribution of the scattering. Scattering from the usually neglected longitudinal field of the guided mode is also analyzed; once included, it allows us to obtain good agreement with the measured data on polarization dependent scattering (PDS). In addition, approximate formulas are developed for estimating the spectral bandwidth and peak loss caused by grating scattering. Scattering analysis based on the coupled-mode theory (CMT) is also established using hybrid HE and EH radiation modes; comparison of results showed that VCM gives good estimates except at very small scatter angles.; Second, nonlinear grating effects with supercontinuum (SC) and femtosecond pulses are studied using gratings imprinted in a microstructure fiber. We observed narrow-band spectral enhancements around the grating resonance, and we are able to associate them to dispersive waves generated during nonlinear grating interaction with individual Raman solitons. A theoretical model based on the nonlinear coupled-mode equations (NLCMEs) is developed; adopting a Bloch-wave approach, we are able to treat the effect of grating structure as a modification to the dispersion of the guided mode.; Last, the use of quantum amplified isomerization (QAI) polymer for waveguide applications is investigated. Using spin coating technique, we are able to fabricate QAI polymer thin films with a low 0.1 dB/cm waveguide loss, and structures such as channel waveguides and holographic gratings are fabricated using direct laser writing. Similar to tilted fiber gratings, we find that the out-coupling efficiency of holographic gratings can be improved significantly with appropriate fringe tilting. In addition, the grating-assisted coupling of scattered light back into channel waveguides is also experimented. |
