Efficient mode coupling technique between photonic crystal heterostructure waveguide and silica waveguides

We report an efficient mode coupling technique between silica waveguides (SWGs) and a planar photonic crystal heterostructure waveguide (PPCHWG) composed of two semi-infinite two-dimensional photonic crystals (PCs) with different filling fractions. By calculating the transmittance at output end of SWG, we find that the designed structures possess the merits of high coupling efficiency and relaxing fabricating tolerance. The maximal transmittance exceeds 90% at a wavelength near 1.65 μm. The high transmission efficiency of PPCHWGs can be achieved without introducing any defect structures for optimal mode matching. Besides, the width of PPCHWGs can be flexibly adjusted via changing the separation of two component PCs in PC heterostructures.