A simple numerical approach for arbitrary profile planar optical waveg
uides based on the wave impedance transformation is presented. The onl
y mathematics involved in this approach is the wave impedance transfor
mation formula, which has been widely used in the field of microwaves.
Because of its simplicity, the method can be implemented into short b
ut effective computer codes. The method is exact when the index profil
es are of step-index shapes and is shown to be very accurate in compar
ison with the exact analytical solutions when the refractive index is
of graded-index profiles.