| In this thesis, diffraction properties of Gaussian laser beams by waveguide grating structure are characterized with experimental verifications. Guided-mode resonance (GMR) devices utilizing thin-film structures with diffractive elements and waveguides exhibit extraordinary filtering capability such as high efficiency, narrow linewidth and extended low sidebands. An infinite plane-wave diffraction model predicts 100% diffraction efficiency for these devices.;For a Gaussian laser beam illumination of a realistic beam source on these devices, diffraction efficiency is expected to be lower than 100% because of high angular selectivity of GMR devices and a certain degree of angular divergence in an analysis of a finite-sized beam. A Gaussian beam diffraction model is formulated in order to address this problem by the angular spectrum representation of incident and diffracted finite-sized beam and to suggest high-efficiency GMR filter design under Gaussian beam. Additionally, the spatial properties of a Gaussian laser beam by the GMR filters are examined by considering design problems. For the verifications, this finite-sized beam is applied to a double-layer optical reflection filter and microwave reflection and transmission filter. |
