High Extinction Ratio Polarization Beam Splitter Design by Low-Symmetric Photonic Crystals

Abstract

A novel concept of polarization beam splitting with high polarization extinction ratio is proposed based on the polarization sensitive self-collimation feature of symmetry reduced photonic crystals. The idea utilizes self-collimation mechanism and rotated isofrequency contours arising due to the deliberately implemented symmetry reduction in the photonic structure. Square lattice of low-symmetric rectangular air holes in dielectric background are numerically analyzed in both frequency and time domains. The operating bandwidth of the device is Delta lambda = 53 nm. At lambda = 1.55 mu m, polarization extinction ratios are similar to 23 and similar to 18 dB for transverse electric and transverse magnetic ports, respectively. The investigated device is 46.4 mu m x 12.4 mu m in size and based on a uniform, planar, and homogenous structure. Therefore, there is no need for an additional splitting assistance to separate the two orthogonal polarizations. Possible fabrication imperfections are also analyzed and it is observed that polarization extinction ratios stay above 17 dB when error percentage is around 5.5%. With having these advantages, symmetry reduced photonic crystal-based polarization beam splitters can be a good candidate for optical communication applications.