  We introduce a new fundamental property of waveguides induced by the forces
of the guided light, namely, the ability to self align or be in instability. A
nanoscale waveguide broken by an offset and a gap may tend to self align to
form a continuous waveguide. Conversely, depending on the geometry and light
polarization, the two parts of the waveguide may be deflected away from each
other, thus being in an unstable state. These effects are unique as they rely
on the presence of both the guided mode and the scattered light. Strong self
alignment forces may be facilitated by near field interaction with polarization
surface charges.
