Fig. 7: Relation between bend-transmission and C-points (CPs).
a Schematic illustration of linear polarization causing low transmittance via the bend of a conventional W1WG, b Schematic illustration of polarization singularities causing high transmittance via the bend of an S = −2 IS-PhCWG (in the upper band). The red and blue arrows represent the directions of polarization. Black dotted lines indicate the connection interface of the 120-degree bend. c The simulation results of CP distributions in S = −2 IS-PhCWG. Red, green, and blue lines show the zero values of S1, S2, and S3, respectively. Black boxes show the location of CPs. Gray boxes show the location of VPs. Color maps show the amplitude of electric fields in the waveguide. Black dotted lines show the connection interfaces of a 120-degree bend. The normalized frequencies, the normalized amplitudes of the electric field, and the bend-transmittances are shown below each plot.
