Numerical studies of 2D photonic crystals: Waveguides,coupling between waveguides and filters |
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Authors: | Stoffer R Hoekstra HJWM De Ridder RM Van Groesen E Van Beckum FPH |
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Institution: | (1) University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands |
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Abstract: | In photonic crystals, light propagation is forbidden in a certain wavelength range, the bandgap. In a two-dimensional crystal composed of parallel high-refractive index rods in a low-index background a line defect can be formed by removing a row of these rods, which can act as a waveguide for frequencies in the bandgap of the crystal. In order to get more insight into the main features of such waveguides we have studied a number of properties, using simulation tools based on the finite difference time domain method and a finite element Helmholtz solver. We show conceptually simple methods for determining the bandgap of the crystal as well as the dispersion of a waveguide for wavelengths in this bandgap. For practical applications, it is also important to know how much light can be coupled into the waveguide. Therefore, the coupling of light from a dielectric slab waveguide into the photonic crystal waveguide has been examined, showing that a coupling efficiency of up to 83% can be obtained between a silicon oxide slab and a waveguide in a crystal of silicon rods. Finally, calculations on an ultra-compact filter based on reflectively terminated side-branches of waveguides (similar to tuned stubs in microwave engineering) are shown and discussed. |
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Keywords: | numerical modelling photonic bandgap crystals wavelength filter |
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