We report on the observation of Bloch oscillations in light transport through periodic dielectric systems. By introducing a linear refractive index gradient along the propagation direction the optical equivalent of a Wannier-Stark ladder was obtained. Bloch oscillations were observed as time-resolved oscillations in transmission, in direct analogy to electronic Bloch oscillations in conducting crystals where the Wannier-Stark ladder is obtained via an external electric field. The observed oscillatory behavior is in excellent agreement with transfer matrix calculations.

We report on the observation of time resolved Bloch oscillations of light waves in optical superlattice structures. The structures are series of coupled microcavities, which are grown in porous silicon with high control of optical parameters. A controlled linear gradient of refractive index along the growth direction was maintained to tilt the photonic band gap of the superlattice. This is in perfect analogy to the tilted electronic miniband structure of a semiconductor in an electric field. In this way an optical Wannier-Stark ladder of equidistant optical modes was formed. Their frequency separation defines the period of the photon Bloch oscillations. The experimental results are in excellent agreement with transfer matrix calculations. The observed phenomenon is the optical counterpart of the well known electronic Bloch oscillations. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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We report on optical analogues of well-known electronic phenomena such as Bloch oscillations and electrical Zener breakdown. We describe and detail the experimental observation of Bloch oscillations and resonant Zener tunneling of light waves in static and time-resolved transmission measurements performed on optical superlattices. Optical superlattices are formed by one-dimensional photonic structures (coupled microcavities) of high optical quality and are specifically designed to represent a tilted photonic crystal band. In the tilted bands condition the miniband of degenerate cavity modes turns into an optical Wannier-Stark ladder (WSL). This allows an ultrashort light pulse to bounce between the tilted photonic band edges and hence to perform Bloch oscillations, the period of which is defined by the frequency separation of the WSL states. When the superlattice is designed such that two minibands are formed within the stop band, at a critical value of the tilt of photonic bands the two WSLs couple within the superlattice structure. This results in a formation of a resonant tunneling channel in the minigap region, where the light transmission boosts from 0.3% to over 43%. The latter case describes the resonant Zener tunneling of light waves.