Performance analysis of polarization transformation waveguide structures for planar light circuits

Abstract

Polarization management is an important issue in current planar light circuit as there are many photonic devices that only work with one type of polarization and also there is much effort to increase network capacity by polarization division multiplexing. Polarization transformers are the most important and challenging elements to realize polarization diversity systems. In this paper we introduce stepped waveguide approach to polarization rotation as a promising method regarding device compactness and fabrication complexity, then structures reported in literature which are based on this concept are reviewed and analyzed. Furthermore we use this approach to propose a novel structure for polarization rotation in low index contrast substrates of silica-on-silicon, with an index contrast of 0.75, to lower the polarization dependence loss of devices realized in such substrates. This new design promises a conversion efficiency of 99 % over 854 um at the wavelength of 1.55 um within a CMOS compatible fabrication procedure.