Photonic bloch oscillations and Zener tunnelling
Bloch oscillations and Zener tunneling are the two fundamental phenomena associated with the propagation of waves and quantum particles in periodic media under the action of an external driving force. Bloch oscillations occur when an external force causes the particle to gain momentum and to approach the Bragg resonance, where it is scattered back. The strongest Zener tunneling takes place when the particle reaches the edge of the first Brillouin zone where the band gap is the smallest. The periodic distribution of the refractive index plays the role of a crystalline potential, and the index gradient causes the beam to move across the structure when it experiences Bragg reflection on the high-index and total internal reflection on the low index side of the structure. The tunneled and oscillating parts are well identified in the Fourier domain, where the main part of the beam oscillates inside the first Brillouin zone, while the tunneled parts are distributed in higher o rder bands.