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Some of the simplest light-harvesting systems in nature rely on the presence of surface structures to increase internal light scattering. We have extended this concept to increase the efficiencies of man-made solar energy harvesting systems. Specifically, we exploit the wrinkles and deep folds that form on polymer surfaces when subjected to mechanical stress to guide and retain light within the photo-active regions of photovoltaics. Devices constructed on such surfaces show substantial improvements in light harvesting efficiencies, particularly in the near-infrared region where light absorption is otherwise minimal. We report a vast increase in the external quantum efficiency of polymer photovoltaics by more than 600% in the near-infrared, where the useful range of solar energy conversion is extended by more than 200 nm. This method of exploiting elastic instabilities of thin, layered materials is straightforward and represents an economical route to patterning photonic structures over large areas to improve the performance of optoelectronics. [ABSTRACT FROM AUTHOR]

From night vision and objects overwhelmed by sunlight to jammed signals and those that are purposely encrypted, detecting low-level or hidden signals is a fundamental problem in imaging. Here, we develop and exploit a new type of stochastic resonance, in which nonlinear coupling allows signals to grow at the expense of noise, to recover noise-hidden images propagating in a self-focusing medium. The growth rate is derived analytically by treating the signal–noise interaction as a photonic beam–plasma instability and matches experimentally measured resonances in coupling strength, noise statistics and modal content of the signal. This is the first observation of nonlinear intensity exchange between coherent and spatially incoherent light and the first demonstration of spatial coherence resonance for a dynamically evolving signal. The results suggest a general method of reconstructing images through seeded instability and confirm information limits predicted, but not yet observed, in nonlinear communications systems. [ABSTRACT FROM AUTHOR]

We study the dynamics of phasons in a nonlinear photonic quasicrystal. The photonic quasicrystal is formed by optical induction, and its dynamics is initiated by allowing the light waves inducing the quasicrystal to nonlinearly interact with one another. We show quantitatively that, when phason strain is introduced in a controlled manner, it relaxes through the nonlinear interactions within the photonic quasicrystal. We establish experimentally that the relaxation rate of phason strain in the quasicrystal is substantially lower than the relaxation rate of phonon strain, as predicted for atomic quasicrystals. Finally, we monitor and identify individual ‘atomic-scale’ phason flips occurring in the photonic quasicrystal as its phason strain relaxes, as well as noise-induced phason fluctuations. [ABSTRACT FROM AUTHOR]

Nonlinear periodic lattices occur in a large variety of systems, such as biological molecules, nonlinear optical waveguides, solid-state systems and Bose-Einstein condensates. The underlying dynamics in these systems is dominated by the interplay between tunnelling between adjacent potential wells and nonlinearity. A balance between these two effects can result in a self-localized state: a lattice or 'discrete' soliton. Direct observation of lattice solitons has so far been limited to onedimensional systems, namely in arrays of nonlinear optical waveguides. However, many fundamental features are expected to occur in higher dimensions, such as vortex lattice solitons, bright lattice solitons that carry angular momentum, and three-dimensional collisions between lattice solitons. Here, we report the experimental observation of two-dimensional (2D) lattice solitons. We use optical induction, the interference of two or more plane waves in a photosensitive material, to create a 2D photonic lattice in which the solitons form. Our results pave the way for the realization of a variety of nonlinear localization phenomena in photonic lattices and Crystals. Finally, our observation directly relates to the proposed lattice solitons in Bose-Einstein condensates, which can be observed in optically induced periodic potentials. [ABSTRACT FROM AUTHOR]