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

Abstract

Optical couplers are important components for signal distribution in optoelectronic transmitter/receiver modules. Y-junction waveguide is an attractive candidate for optical coupler due to its less wavelength and polarization dependent. However, they suffer from excess loss due to the mode field/wave-front mismatch between the output and input branches. Furthermore, the difference between the outputs according to the mismatch of the optical signal further increases when the optical signal is a multi-channel signal. In addition to the loss due to the mode mismatch, the connection loss due to the corner-bent waveguide also occurs in a conventional Y-branch. Various methods have been proposed to reduce the junction excess loss by modifying the physical geometry of the Y-junction directly. The Y-junction power divider geometry with asymmetry waveguide structure by increasing the rib height of the waveguide only from the inner side of the branches has been proposed [1]. Gamet and Pandraud [2] proposed segemented silica waveguides to reduce loss of the Y-branch. 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.