A channel drop filter using a single defect in a 2-D photonic crystal slab - Defect engineering with respect to polarization mode and ratio of emissions from upper and lower sides

A detailed theoretical analysis of defect engineering in a channel drop filter consisting of a single point defect near a waveguide in a two-dimensional (2-D) photonic crystal (PC) slab is presented. Initially, engineering of the point defect to control the polarization modes of emitted light is examined. By introducing an elliptical defect laterally shifted from the PC lattice, a single linearly polarized light mode can be selected to emit the majority of light, whereas light emitted from the original circular defect is made up of a range of linearly polarized modes. It is also shown that the ratio of light emitted from the top and bottom side of the defect can be improved considerably by introducing a defect with a stepped section along the vertical axis, thereby increasing the net efficiency of the device.