Intrinsic diffraction losses in photonic crystal waveguides with line defects

Intrinsic diffraction losses of linear defect modes in photonic crystal slabs are calculated for membrane-type waveguides with strong refractive index contrast. In the frequency region of high group velocity of the defect mode, the radiative losses increase with the air fraction of the lattice and decrease on increasing the channel width or the slab thickness. Close to a mini-gap in the mode dispersion, a complex frequency dependence of the losses is found. The calculated losses agree well with those measured in a Si slab [M. Loncar , Appl. Phys. Lett. 80, 1689 (2002)]. (C) 2003 American Institute of Physics.