A planar waveguide concave grating employing dielectric mirrors

Dielectric mirrors, which yield high-reflectances on grating facets, are proposed for the design of a planar waveguide concave grating. The transfer-matrix method is used to derive an expression for the reflectance of a series of air slots and high-index stacks. The FullWAVE software, a finite difference time-domain EM solver from R-Soft, is used to evaluate the loss of the resulting 2D waveguide grating. The simulation results show that the polarization-dependent loss (PDL) is below 0.25 dB when the proposed dielectric mirror is used. The influence of the width variation of the dielectric stack is also taken into account.