Guided EM Waves in Anisotropic Dielectric Plates

摘要

Guided electromagnetic waves in an infinite dielectric plate with general crystalsymmetry surrounded by free space are studied in terms of the three-dimensional Maxwell's equations. To exhibit as how the crystal symmetry may affect the propagation and coupling of the waves, the study is divided into four cases. For each case, the closed form solutions are obtained, and dispersion relations and modes are computed and studied. It is found that in Case I, solutions can be separated into the T E and T M waves. And T E and T M waves can be further separated into the symmetric and anti-symmetric waves. In the Case II, the solutions for the T E waves remain the same as those in the Case I. However, TM waves can not be separated into symmetric and anti-symmetric waves. In Case III, solutions can not be separated into the T E and T M waves, but they can still be separated into the symmetric and anti-symmetric waves. In Case IV, solutions can neither be separated into the T E and T M waves nor into the symmetric and anti-symmetric waves. In case the solutions are not separable, the resulting waves can always be expressed as the sum of symmetric and anti-symmetric waves which differ by a phase angle of pi/2. Numerical computations are made for singly and doubly rotated cuts of lithium niobate corresponding to the four cases of symmetry.