A Novel Demultiplexing Design for Coarse WDM: Exploiting Material Dispersion

In this paper, a compact low-cost simple-tofabricate demultiplexer is proposed for coarse wavelength division multiplexing (CWDM). The device consists of two layers of the same semiconductor material: the first layer is homogeneous medium with a given refractive index n2, while the second layer is an inhomogeneous medium, where its refractive index is graded according to a creation profile. The proposed design exploits the ray's spatial shift that results from material dispersion as difference wavelengths propagate through the structure. Through analytical analysis and numerical evaluation, we investigate the effects of the various design parameters on the amount of achieved spatial shift between the adjacent wavelengths and the size of the device. The results show promising results for fourand eight-channel devices operating on the standard CWDM wavelength grid.