Intrinsic modes in tapered optical waveguides

Intrinsic modes are recently developed source-free field solutions in homogeneous wedge-shaped layers with penetrable boundaries. Expressed as spectral integrals over a continuum of plane waves, they can be computed to chart the continuous progress of a propagating wave field as it passes from its well-trapped regime in the wider section to the radiating regime through local cutoff in the narrower part. Intrinsic modes are explored here for application to tapered optical waveguides embedded within different exterior media. Two-dimensional electromagnetic TGE (transverse electric) and TM (transverse magnetic) field solutions are presented and evaluated numerically for small as well as large taper angles and various material parameters. The results reveal the effect of asymmetry in the exterior media on the intrinsic mode shapes, and the control that can be exercised thereby to transfer the optical energy from the taper to the surrounding environment.<>