Design and Characteristics of Directional Coupler Based Filters

In this paper, an accurate characterization of a novel design of an optical wavelength filter is investigated and analyzed by the coupled mode theory (CMT). The effect of the different structure geometrical parameters on the filter performance is studied. The crosstalk and bandwidth of the device are also calculated for various separations between the waveguides. The suggested design has a crosstalk of -34.909 dB and bandwidth of 14.8 nm for device length of 1646.26 μm. A bandwidth of 10 nm can also be obtained with a device length of 3.1 mm. In addition, a novel design of cascaded structure of non-identical directional coupler is introduced and analyzed by the CMT. The suggested design offers complete power exchange between two slab waveguides having modes with different propagation constants. The reported coupler exhibits low crosstalk of -38.38dB with a compact device length