Analytical Design of Total-Internal-Reflection Grating Demultiplexers With a Low Noise Floor

Etched diffraction grating (EDG) demultiplexers using total-internal-reflection (TIR) facets with a low noise floor have theoretically been designed based on silicon nanowire wafers. The transfer function (TF) of EDG demultiplexers is derived based on Fourier analysis. Since the Goos-Hänchen shift and the finite size of facets result in most of the loss of EDG demultiplexers with TIR facets, we can reshape the TF into an approximate Gaussian distribution by slightly adjusting each grating facet´s size and structure. Thus, we design an EDG demultiplexer with a very low noise floor based on silicon waveguide.