It is demonstrated that bent dielectric waveguides can convert inciden
t radiation into guided-mode power. A beam-propagation method simulati
on of the effect in a slab single-moded weakly guiding waveguide is sh
own to be in accordance with a theoretical formulation of the process.
I establish a simple analytical approximation for power captured by a
curved slab guide from an incident Gaussian-shaped beam. The results
demonstrate general agreement with the reciprocity principle: the most
efficient radiator is the best receiver, and radiation incident from
outside the bend couples most efficiently into the guide.