right angle waveguide a second dielectric cylinder with high refractive index is arranged at the corner of the right angle waveguide said second dielectric cylinder is a compensation scattering dielectric cylinder and the compensation reflected waves generated by the second dielectric cylinder are offset by the intrinsic reflected waves in the waveguide without said compensation scattering dielectric said compensation scattering dielectric cylinder is further adopted as an isosceles right triangle cylinder an arch shaped cylinder a square cylinder a triangular cylinder a polygonal cylinder of more than three sides or further a cylinder of which the outline of the cross section is a smooth closed curve said second dielectric cylinder compensation scattering dielectric cylinder is the isosceles right triangle cylinder and the material of said first dielectric cylinders with high refractive index is respectively adopted as si gallium arsenide titanium dioxide or a different dielectric with refractive index of more than 2 and the material of the background dielectric with low refractive index is adopted as air vacuum magnesium fluoride silicon dioxide or a different dielectric with refractive index of less than 1 6 embodiment 1 the lattice constant of said square lattice phc is a said first dielectric cylinders with high refractive index are adopted as square cylinders and the side length of each square cylinder is 0 31a the polarization of optical waves transmitted in the waveguide is te form said second dielectric cylinder is adopted as an isosceles right triangle.