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Guilbert L.,CNRS Laboratory of Optical Materials, Photonics, and Systems
Applied Physics B: Lasers and Optics | Year: 2010

Field-induced light deflection by ferroelectric domain walls in lithium niobate (LN) and lithium tantalate (LT) is theoretically studied. The phenomenon can occur not only when both the incident wave vector k and the electric field E are parallel to the z-axis-as demonstrated by experiments made so far-but also when E and/or k are perpendicular to z. In particular, for E parallel to x and k parallel to y, the deflection phenomenon is predicted to have the same characteristics as in triclinic or monoclinic ferroelastics: the large deflection angle is related to the natural birefringence, whereas the deflection amplitude is proportional to the small tilt angle of the neutral lines, which is here induced by the electric field. In periodic domain structures, interference between deflected waves occurs, and the deflected intensity is expected to be largely enhanced when the Bragg condition is satisfied. This transverse configuration is thus specially attractive to characterize periodically-poled crystals. © 2009 Springer-Verlag. Source

Sciamanna M.,CNRS Laboratory of Optical Materials, Photonics, and Systems | Shore K.A.,Bangor University
Nature Photonics | Year: 2015

This Review Article provides an overview of chaos in laser diodes by surveying experimental achievements in the area and explaining the theory behind the phenomenon. The fundamental physics underpinning laser diode chaos and also the opportunities for harnessing it for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient testbed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified. © 2015 Macmillan Publishers Limited. Source

Virte M.,CNRS Laboratory of Optical Materials, Photonics, and Systems | Virte M.,Free University of Brussels | Panajotov K.,Free University of Brussels | Panajotov K.,Bulgarian Academy of Science | And 2 more authors.
Nature Photonics | Year: 2013

Fifty years after the invention of the laser diode, and forty years after the butterfly effect signified the unpredictability of deterministic chaos, it is commonly believed that a laser diode behaves like a damped nonlinear oscillator and cannot be driven into chaotic operation without additional forcing or parameter modulation. Here, we counter that belief and report the first example of a free-running laser diode generating chaos. The underlying physics comprises a nonlinear coupling between two elliptically polarized modes in a vertical-cavity surface-emitting laser. We identify chaos in experimental time series and show, theoretically, the bifurcations leading to single- and double-scroll attractors with characteristics similar to Lorenz chaos. The reported polarization chaos resembles noise-driven mode hopping, but shows opposite statistical properties. Our findings open up new research areas for the creation of controllable and integrated sources of optical chaos. © 2013 Macmillan Publishers Limited. Source

Biaggio I.,Lehigh University | Coda V.,CNRS Laboratory of Optical Materials, Photonics, and Systems | Montemezzani G.,CNRS Laboratory of Optical Materials, Photonics, and Systems
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

We describe and analyze a quasi-phase-matching scheme for nonlinear optical frequency conversion where the spatial modulation of mode intensity in coupled parallel waveguides provides the required modulation in the generation of the frequency conversion signal, instead of a variation of any material parameter or propagation constant. We analyze this coupling-length phase-matching (CLPM) scheme both for second-order frequency conversion, such as second harmonic generation or difference-frequency generation, as well as for third-order four-wave mixing processes, for which we consider the example of generating a longer wavelength by third-order nonlinear mixing of two shorter wavelength waves. Numerous phase-matching conditions are identified in each case. We show that the maximum photon conversion efficiencies reached after an optimum propagation length are always higher than half those obtained for perfect phase matching in a single waveguide, with nearly 100% photon conversion possible for several of the CLPM conditions we studied. © 2014 American Physical Society. Source

Joseph C.,CNRS Laboratory of Optical Materials, Photonics, and Systems | Bourson P.,CNRS Laboratory of Optical Materials, Photonics, and Systems | Fontana M.D.,CNRS Laboratory of Optical Materials, Photonics, and Systems
Journal of Raman Spectroscopy | Year: 2012

Many of the interesting properties that make Ta 2O 5 a strategic material for current and future applications in chemistry, microelectronics and optics, depend on its structural characteristics. In this work, we use Raman spectroscopy to probe structural modifications in amorphous Ta 2O 5 coatings submitted to thermal annealing. On the basis of previous knowledge on the crystalline material, we perform Raman spectrum simulations in disordered and partially ordered Ta 2O 5 from a phonon density of states. Calculated spectra are in good agreement with complex experimental spectra. Our original approach allows assignment of the vibrational features of the amorphous material, and quantitative interpretation of observed structural modifications in terms of ordering scales. In addition, it provides numerical indicators to analyse amorphous to crystalline phase transformation. Copyright © 2012 John Wiley & Sons, Ltd. Source

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