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 thermo-optic polymer array was obtained by applying a temperature gradient. Bloch oscillations manifesting themselves as transverse oscillations of the propagating 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.