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Optica Applicata, Vol. 39, 2009, nr 2, s. 307-317
In this paper, a 60° waveguide bend is designed in a two-dimensional (2D) photonic crystal (PC) slab to provide high transmission over a large bandwidth. We apply geometrical modification in the bend region to improve the transmission characteristics. This modification results in increasing the relative bandwidth from 6.5% to 25.7% of photonic band gap width. Using the effective refractive index, the structures designed are simulated by the 2D finite-difference time-domain (FDTD) method. As a specific application, we use the improved bend structure in a PC waveguide directional coupler and show that the drop output increases significantly.