Light deflection by photonic crystals

When propagating through periodically structured media, i. e. photonic crystals, optical waves will be modulated with the periodicity. As a result, the dispersion of waves will no longer behave as in a free space, and so called frequency band structures appear. Under certain conditions, waves may be prohibited from propagation in certain or all directions, corresponding to partial and complete bandgaps respectively. Here we report a new fascinating phenomenon associated with the partial gaps, that is, deflection of optical waves. This phenomenon will render novel applications in manipulating light flows.