Optical Bloch oscillations in temperature tuned waveguide arrays

We report the observation of optical Bloch oscillations in waveguide arrays . The required linear variation of the propagation constant across the ther mo-optic polymer array was obtained by applying a temperature gradient. Blo ch oscillations manifesting themselves as transverse oscillations of the pr opagating light beam can be attributed to the existence of localized states (Wannier-Stark states) with equidistant eigenvalue spacing (Wannier-Stark ladder). The period and amplitude of the oscillations can be controlled by varying the temperature gradient.