Three different grating tilting formulas for predicting the optimum grating tilt angle for strong mode coupling in planar waveguide gratings are derived. The optimum tilt angles obtained by the ray-optics approach deviate ~1° for transmissive mode coupling and ~1.5° for reflective mode coupling from those computed by the coupled-mode approach. The coupled-mode analysis and ray-optics analysis of the tilted planar waveguide gratings show that the transmissive planar waveguide gratings should be tilted more than 84° for strong TE<sub>0</sub>-to-TE<sub>μ</sub> mode coupling near 1550 nm.
© 2000 Optical Society of America
(050.0050) Diffraction and gratings : Diffraction and gratings
(060.2340) Fiber optics and optical communications : Fiber optics components
(230.1950) Optical devices : Diffraction gratings
(230.7390) Optical devices : Waveguides, planar
Kyung Shik Lee, "Mode Coupling in Tilted Planar Waveguide Gratings," Appl. Opt. 39, 6144-6149 (2000)