Low loss 1×2 optical coupler based on cosine S-bend with segmented waveguide

This paper presents optical coupler which is formed of segmented waveguide to reduce effective refractive index in the branching region and modified cosine S-bend to provide smooth connection to the tapered waveguide. The optical coupler comprises straight polymer waveguide as the input waveguide, tapered waveguide (Lt), modified cosine S-bend (Lc) and linear waveguide (Lh). At the branching point, N short waveguides with small width (a) are introduced to reduce evanescent field. Buried square core (BSC) waveguide with dimension of 7x7 μm was used for the input waveguide, cosine S-bend and linear waveguide. Simulation is done by using beam propagation method (BPM) at wavelength range of 1470-1550 nm.