Study on asymmetric wavelength division de-multiplexer based on directional coupling in slot waveguides

We propose an asymmetric 1$\times $ 2 wavelength division de-multiplexer(WDDM) based on directional coupling in slot waveguides. And we also analyze the transmission characteristics of the device by the finite difference time domain(FDTD). We can find this 1$\times $ 2 WDDM has a high transmittance at the output ports from the numerical results, which is greater than 93% with no structural optimization is required. Then, we can get an asymmetric 1$\times $ 4 WDDM by cascading three asymmetric 1$\times $ 2 WDDMs. Asymmetric structure makes the device more compact. The WDDMs we proposed are supposed to have more applications in integrated optics.