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We propose the hybrid integration of an air hole photonic crystal (PhC) structure with a high Δ (0.75%) single-mode silica waveguide to achieve an ultracompact high efficiency 90° bend for transverse-magnetic polarized light. Diffraction from the periodic boundary between the PhC and silica waveguide regions is shown to seriously degrade the optical efficiency of the bend. A microgenetic algorithm (μGA) combined with a two-dimensional finite-difference time-domain method is used to modify the PhC and its boundary layer to suppress this diffraction which in turn maximizes bend efficiency. The final optimized structure has a 99.4% bend efficiency at a wavelength of 1.55 μm and occupies an area of only 27 × 27 μm.