Polychromatic light localisation in periodic structures

Abstract

Photonic structures with a periodic modulation of the optical refractive index open novel possibilities for designing the fundamental aspects of optical wave dynamics [1]. They offer important opportunity for spatial beam control, including manipulation of beam refraction and diffraction. The physics of beam propagation in periodic photonic structures is governed by the scattering of waves from the high refractive index regions and the subsequent interference of the scattered waves. This is a resonant process, which is sensitive to both the frequency and the propagation angle. In photonic crystals, for example, there appear sharp spectral features where the propagation of optical signals is highly sensitive to the wavelength. As such, most of the demonstrated effects of spatial beam manipulation in periodic structures are primarily optimised for a narrow-frequency range. In many practical cases, including ultra-broad bandwidth optical communications, manipulation of ultra-short pulses or supercontinuum radiation, the bandwidth of the optical signals can span over a wide frequency range. This motivates the studies on the propagation of broad-bandwidth optical beams in periodic photonic structures. The strong dispersion of waves in periodic structures can lead to enhanced spatial separation of the spectral components of the incident light, an effect known as superprism [2, 3]. Importantly, the wave dispersion and diffraction can be balanced or enhanced in materials with nonlinear optical response, thus opening opportunities for all-optical spectral management [4]. The non-linear spatial control of polychromatic light represents an intriguing physical problem, and is the main scope of our studies. In this review we present, what we believe is the first experimental demonstration of nonlinear control of broadband and supercontinuum light in spatially-extended periodic photonic structures, as well as provide theoretical description of the observed phenomena. © 2009 Springer-Verlag Berlin Heidelberg.