Bending losses of dielectric slab optical waveguide with double or multiple claddings: theory.

Bending-loss formulas of a multilayer planar optical waveguide are obtained on the basis of continuation of wave functions without solving the complicated eigenvalue equation. We then consider the bending losses of a doubly clad slab waveguide in which the core has the largest refractive index, and the inner cladding has the lowest. Bending losses are shown to be drastically reduced by inserting low-index inner claddings between the core and the outer cladding.