Waveguide optical polarization splitter using microprism consisting of dielectric multilayer

Abstract

A new type of waveguide optical polarization splitter is proposed and investigated theoretically. The waveguide optical polarization splitter is composed of a Y branch waveguide and a microprism consisting of a dielectric periodic multilayer. As the dielectric periodic multilayer has large birefringence, the TM (x) - and TE (y) - polarized propagating waves are refracted with different angle each other at the microprism. This is the principle of the proposed waveguide polarization splitter. First we have designed the waveguide polarization splitters. An asymmetric Y branch, in which one output port is a straight waveguide for an input waveguide and the other is an abruptly bending waveguide, is used for the design. The refractive indices of the core and cladding (substrate) are 1.51 and 1.509, respectively. The dielectric periodic multilayer for the microprism has been designed so as the effective refractive index for the x-polarization become equal to the refractive index of the substrate. Therefore the x-polarized wave propagates for the output port consisting of the straight waveguide with low loss. The prism has been designed by using the method for the microorism-type of bending waveguide proposed by C.T. Lee and J.M. Hsu so as the y-polarized wave can propagate for the port consisting the abruptly bending waveguide with low loss. Finally we have calculated optical losses for the x- and y-polarizations by using a beam propagating method. The insertion losses of the typically designed waveguide optical polarization splitter for the x-and y-polarizations are 0.14 dB and 0.2 dB, respectively. It has also been confirmed that the crosstalks are <-35 dB for both polarizations.