Slow light in periodic superstructure Bragg gratings

Abstract

A theoretical and experimental analysis of group velocity reduction in periodic superstructure Bragg gratings is presented. Experimental demonstration of group velocity reduction of sub-nanosecond pulses at the wavelength of optical communications is reported using a Moiré fiber grating.

Photonic realization of the relativistic Kronig-Penney model and relativistic Tamm surface states

“…The circumstance that the effects of the δ barriers disappear in the DiracKronig-Penney model when V 0 is an integer multiple π is simply due to the fact that, under such a condition, the phase slips are integer multiplies of 2π, and thus the grating has no phase defects and mimics the dynamics of a one-dimensional free relativistic Dirac particle. It should be noticed that, in another physical context, superstuctured FBGs comprising a periodic sequence of π phase slips, corresponding to the special case V 0 = π/2, have been recently proposed and demonstrated to realize light slowing down [31,32]; however, their connection to the Dirac-Kronig-Penney model was not noticed. It should be also noticed that any FBG structure has a finite length L, and thus some kind of lattice truncation should be introduced in the idealized model.…”

“…As shown e.g. in [31,32], apodization of the FBG amplitude profile ( ), obtained by slowly decreasing ( ) from its constant value ( ) = 0 in the uniform grating region to zero at → ±∞, enables to adiabatically inject and eject light waves in the uniform grating region avoiding truncation effects. Correspondingly, the band structure of the Dirac-Kronig-Penney model is mapped into the alternation of stop/transmission bands observed in spectrally-resolved transmission measurements of the FBG.…”

Dual-Periodic Photonic Crystal Structures

“…In both shallow gratings with long-range modulation in fibers (Sipe et al, 1994;Janner et al, 2005) and in our PhSC, the forward and backward (locally) propagating waves continuously scatter into each other. The advantage of CMT is that it considers the amplitudes of the forward and backward waves directly.…”

“…These adjustable parameters allow one to control the dispersion in the band, and hence v g , without significant detrimental effects associated with the second order dispersion. A periodic arrangement of structural defects in the photonic crystal, described in (iii), creates a dual-periodic photonic super-crystal (PhSC) with short-range quasi-periodicity on the scale of the lattice constant and with long-range periodicity on the defect separation scale (Shimada et al, 2001;Kitahara et al, 2004;Shimada et al, 1998;Liu et al, 2002;Sipe et al, 1994;Benedickson et al, 1996;Bristow et al, 2003;Janner et al, 2005;Yagasaki et al, 2006). These structures usually need to be constructed with the layer-by-layer technique (or, more generally, serially) which is susceptible to the fabrication errors similarly to the other approaches (i,ii) above.…”

“Ideal” optical delay lines based on tailored-coupling and reflecting, coupled-resonator optical waveguides

“…"Slow light" can be achieved in engineered structures which bounce light back and forth as it propagates. Such structures include grating structures [2,3], photonic crystal waveguides [4], and coupled-resonator optical waveguides (CROWs) [5]. The general characteristic of these slow-light waveguides is a dispersion curve ωβ whose slope dω∕dβ, equal to the modal group velocity, is small over a range of frequencies.…”