| Summary: | 碩士 === 國立臺灣大學 === 電機工程學系 === 86 === The finite element (FEM) is used to theoretically investigate the
propagation characteristics of both linear and nonlinear multiple
quantum well (MQW) semiconductor optical waveguides in this research.
Due to the absence of a well-defined formula for modeling the
dependence of the refractive index on the quantum effects, we treat
the MQW as a multilayer one with the refractive index of each thin
layer taken to be that of the corresponding bulk material but with a
modified anisotropic factor. When analyzing a slab MQW waveguide,
numerical solutions of the effective refractive index, the birefringence,
and the intensity-dependent dispersion relations are obtained. By using
a truncation method to handle the infinite boundary, the scalar FEM is
also utilized to study the three-dimensional ridge-loading MQW waveguides.
Solution of the effective refractive index and the birefringence can
be accurately obtained. We discuss the waveguide characteristics for
various layered structures and wavelengths. Directional couplers
consisting of two identical ridge-loading waveguides are studied
and the effect of the degree of symmetry on the operation of these
couplers is examined as well. Power transfer behaviors between the
two waveguides including the possible polarization and wavelength
beamsplitting are examined. Finally, several applications such as
the optical switches and logic gates using the nonlinear material
properties of the waveguide structure are discussed.
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