Superluminal pulse propagation in linear and nonlinear photonic grating structures

Abstract

Optical pulse propagation in photonic grating structures can show anomalous (i.e., superluminal or negative) group velocities under certain circumstances owing to the anomalous dispersive properties induced by the periodic grating structure. Such phenomena can be observed for either linear pulse propagation in passive dielectric grating structures, such as in fiber Bragg gratings (FBGs), as well as in frequency-conversion processes exploiting second-order cascading effects in quasi-phase-matched (QPM) nonlinear crystals. Engineering of the grating structure can be exploited to observe a wide variety of anomalous pulse transmission and reflection behaviors. In this article, we review the main recent experimental and theoretical achievements obtained by our group in this field. In particular, we report on superluminal propagation of picosecond optical pulses at the 1.5-m wavelength of optical communications in FBGs, both in transmission and reflection configurations, with the observation of group velocities as large as 5 0. We also show that the phenomenon of transparent pulse propagation at a negative group velocity in a gain doublet atomic amplifier, recently observed in cesium vapor by Wang and co-workers (L. J. Wang, A. Kuzmich, and A. Dogariu, Nature vol. 406, pp. 277-279, 2000), can be achieved as well in a photonic parametric amplifier by exploiting the anomalous dispersive properties of the amplifier induced by a suitably designed QPM grating profile.

Matrix analysis of microring coupled-resonator optical waveguides

“…[23,6] In the time domain, the main (highest) peak of the output pulse does indeed appear before the peak of the input pulse. Figure 9 shows the output pulses at the through and drop ports as well as in the input pulse.…”

Slow and fast light in optical fibers using acoustooptic coupling between two co-propagating modes

“…9 This has recently been demonstrated experimentally for linear and nonlinear gratings. [10][11][12] We here show numerically that pulse delays and advancements can be obtained in optical fibers using acoustooptic coupling between two co-propagating optical modes. 13 A single acoustooptic interaction region, and a configuration based on two acoustooptic interaction regions, separated by a section of unperturbed fiber, are simulated.…”

Active control of transmission and group velocity in one-dimensional photonic crystals

“…In these investigations, the main focus was on the transmission of a pulse through the medium. In experiments, Longhi et al [12,13] first observed superluminal reflection of an optical pulse by using a double-Lorentzian fiber Bragg grating. Later, Nimtz et al [14] experimentally verified that the reflection delay was almost independent of the barrier's length (this effect is known as the Hartman effect [15]).…”