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We have investigated and optimized a 60-waveguide bend that is implemented in a planar photonic crystal (PhC) with triangular lattice symmetry. The in-plane guiding within the planar PhC stucture is based on a W1 defect waveguide (a single line defect acting as a light channel in the GK-direction) whereas for the vertical light confinement we rely in a slab waveguide formed by the low index contrast material system InGaAsP/InP. To achieve a reasonable bandgap around 1.55 mm the PhC consists of a lattice of holes with a filling factor of 39%. Our simulations are carried out in the frequency domain with the 2D multiple multipole (MMP) method. We show a significant improvement in both the transmission efficiency (up to 96.8%) and the transmission bandwidth by performing an optimization based on a sensitivity analysis. The most promising structure was afterwards simulated with a 3D-FDTD program, where we achieved transmission efficiency that peaks at 66%.

A major drawback of conventional dielectric waveguides is that their bending radii are limited to several millimeters due to the degradation of total internal reflection. Since the guiding of light in a PhC defect waveguides is not given through total internal reflection but the photonic bandgap (PBG) effect they can provide bending within the subwavelength range. Hence, PhC waveguides offer a promising scheme for low loss and ultra-dense optical integration. Instead of the 3D-PhC structures that are difficult to fabricate 2D planar PhC system are widely used [1], where the in-plane guiding is provided by the photonic crystal and the vertical light confining is warranted by a slab waveguide …