21 research outputs found
Two-color nonlinear localized photonic modes
We analyze second-harmonic generation (SHG) at a thin effectively quadratic
nonlinear interface between two linear optical media. We predict multistability
of SHG for both plane and localized waves, and also describe two-color
localized photonic modes composed of a fundamental wave and its second harmonic
coupled together by parametric interaction at the interface.Comment: 4 pages, 5 figures (updated references
Engineered nonlinear lattices
We show that with the quasi-phase-matching technique it is possible to fabricate stripes of nonlinearity that trap and guide light like waveguides. We investigate an array of such stripes and find that when the stripes are sufficiently narrow, the beam dynamics is governed by a quadratic nonlinear discrete equation. The proposed structure therefore provides an experimental setting for exploring discrete effects in a controlled manner. In particular, we show propagation of breathers that are eventually trapped by discreteness. When the stripes are wide the beams evolve in a structure we term a quasilattice, which interpolates between a lattice system and a continuous system.Peer ReviewedPostprint (published version
Quasiperiodic Envelope Solitons
We analyse nonlinear wave propagation and cascaded self-focusing due to
second-harmonic generation in Fibbonacci optical superlattices and introduce a
novel concept of nonlinear physics, the quasiperiodic soliton, which describes
spatially localized self-trapping of a quasiperiodic wave. We point out a link
between the quasiperiodic soliton and partially incoherent spatial solitary
waves recently generated experimentally.Comment: Submitted to PRL. 4 pages with 5 figure
Approximate solutions and scaling transformations for quadratic solitons
We study quadratic solitons supported by two- and three-wave parametric
interactions in chi-2 nonlinear media. Both planar and two-dimensional cases
are considered. We obtain very accurate, 'almost exact', explicit analytical
solutions, matching the actual bright soliton profiles, with the help of a
specially-developed approach, based on analysis of the scaling properties.
Additionally, we use these approximations to describe the linear tails of
solitary waves which are related to the properties of the soliton bound states.Comment: 11 pages, 9 figures; submitted for publicatio
Parametric localized modes in quadratic nonlinear photonic structures
We analyze two-color spatially localized modes formed by parametrically
coupled fundamental and second-harmonic fields excited at quadratic (or chi-2)
nonlinear interfaces embedded into a linear layered structure --- a
quasi-one-dimensional quadratic nonlinear photonic crystal. For a periodic
lattice of nonlinear interfaces, we derive an effective discrete model for the
amplitudes of the fundamental and second-harmonic waves at the interfaces (the
so-called discrete chi-2 equations), and find, numerically and analytically,
the spatially localized solutions --- discrete gap solitons. For a single
nonlinear interface in a linear superlattice, we study the properties of
two-color localized modes, and describe both similarities and differences with
quadratic solitons in homogeneous media.Comment: 9 pages, 8 figure
Three-wave interaction in two-component quadratic nonlinear lattices
We investigate a two-component lattice with a quadratic nonlinearity and find with the multiple scale
technique that integrable three-wave interaction takes place between plane wave solutions when these fulfill
resonance conditions. We demonstrate that energy conversion and pulse propagation known from three-wave
interaction is reproduced in the lattice and that exact phase matching of parametric processes can be obtained
in non-phase-matched lattices by tilting the interacting plane waves with respect to each other.info:eu-repo/semantics/publishedVersio
Continuous monitoring of summer surface water vapor isotopic composition above the Greenland Ice Sheet
We present here surface water vapor isotopic measurements conducted from June to August 2010 at the NEEM
(North Greenland Eemian Drilling Project) camp, NW Greenland (77.45 degrees N, 51.05 degrees W, 2484 m a.s.l.).
Measurements were conducted at 9 different heights from 0.1m to 13.5m above the snow surface using two different types of cavity-enhanced near-infrared absorption spectroscopy analyzers. For each instrument specific protocols were developed for calibration and drift corrections. The inter-comparison of corrected results from different instruments reveals excellent reproducibility, stability, and precision with a standard deviations of similar to 0.23 parts per thousand for delta O-18 and similar to 1.4 parts per thousand for delta D. Diurnal and intraseasonal variations show strong relationships between changes in local surface humidity and water vapor isotopic composition, and with local and synoptic weather conditions. This variability probably results from the interplay between local moisture fluxes, linked with firn-air exchanges, boundary layer dynamics,
and large-scale moisture advection. Particularly remarkable are several episodes characterized by high (> 40 parts per
thousand) surface water vapor deuterium excess. Air mass back-trajectory calculations from atmospheric analyses and water tagging in the LMDZiso (Laboratory of Meteorology Dynamics Zoom-isotopic) atmospheric model reveal that these events are associated with predominant Arctic air mass origin. The analysis suggests that high deuterium excess levels are a result of strong kinetic fractionation during evaporation at the sea-ice margin