Emission of radiation from a tapered edge of an optical waveguide

An analysis is made of the coupling of radiation out of a smoothly tapered optical waveguide. It is shown experimentally that energy is extracted because of scattering of the guided modes in the tapered region when the thickness exceeds a critical value and because of emission of guided modes when the thickness is below this value. An investigation is reported of the far-field pattern of the radiation as a function of the taper angle of the waveguide. The experimental results are compared with calculations.