The connection between radiation pressure and dispersion in dielectric waveguides

Through use of the response theory of optical forces, we show that radiation pressure generated within step index waveguides can be computed exactly and simply from the waveguide dispersion. In the absence of electrostrictive effects, we show that optical forces are only manifest on the boundaries of a dielectric waveguide. As a consequence, the principle of virtual work can be used to express the total optical force (or mean radiation pressure) acting on the boundaries of the waveguide in terms of the modal effective index. Through use of this relationship, exact agreement is found between the optical forces computed using waveguide dispersion and with the Maxwell stress tensor.