Unique properties of quadratic solitons

Quadratic spatial solitons exist in media with second order nonlinearities near the phase-matching condition for frequency mixing processes involving two or three waves of different frequency. Discussed here are a number of properties of these special solitons which are different from those of other spatial solitons which rely on optically induced index changes for guiding. First, the self-guiding properties of quadratic solitons are shown to have completely different origins than solitons which rely on index changes. Second, it is shown that there exists a large variety of quadratic solitons which contain two or three distinct spectral components with relative amplitudes depending on the phase mismatch, dimensionality of the propagation geometry, the soliton power and the launching conditions. Third, under appropriate conditions, solitons can be formed even when the group velocity directions for the spectral components lead to walk-off under normal circumstances. Fourth, for type II phase-matching in bulk crystals, seeded interactions lead to saturating amplifier characteristics

Measurement Of Modulational Instability Gain Of Second-Order Nonlinear Optical Eigenmodes In A One-Dimensional System

Amplification of a spatially periodic perturbation on a wide fundamental beam was studied to investigate the gain coefficients of spatial modulational instability (MI). The MI was measured in a one-dimensional medium with a quadratic nonlinearity. The gain coefficients were measured as a function of periodicity, intensity, and wave-vector mismatch

Spatial Modulational Instability In One-Dimensional Linbo3 Slab Waveguides

An experimental study was carried out to demonstrate the occurrence of modulational instability (MI) during second haronic generation (SHG) in LiNbO3 slab waveguides. The experiment was performed with 20 psec pulses at 1.32 μm

Spatial Modulational Instability In One-Dimensional Lithium Niobate Slab Waveguides

We report an experimental study of the breakup through modulational instability of broad fundamental beams near the phase-matching condition for second-harmonic generation in lithium niobate slab waveguides. Two mechanisms for initiating modulational instability, waveguide imperfections and noise on the input beam, are identified. © 2000 Optical Society of America

Fission Of Narrow High Power Beams Into Multiple Solitons In A Second-Order Nonlinear Slab Waveguide

Summary form only given. One of the first nonlinear effects observed was the break-up of wide, high intensity, beams into filaments due to spatial noise present on the beam, known as modulational instability (MI), that generally occurs in any media with nonlinearities which lead to self-focusing. We have recently reported observation of MI near the phase-matching condition for second-harmonic generation in LiNbO3 slab waveguides. For narrow beams, a different phenomenon can occur at lower intensities than MI, namely the fission of the beam into multiple solitons. For spatial solitons, the peak soliton intensity varies inversely with the soliton\u27s spatial width, so that if the input beam contains sufficient intensity to generate multiple solitons, fission occurs. Here we report experimental observation of the break-up of high intensity beams into multiple components at thresholds consistent with soliton fission

Observation of two-dimensional quadratic spatial solitons in type I potassium niobate

A c-plate KNbO3 crystal cut for non-critical phase matching for an a-polarized fundamental at a wavelength of 985 nm for a crystal temperature of 31.4 °C was studied. Quadratic spatial solitons (QSS) were formed while exiting the back face of the KNbO3 crystal. The beam waist of the fundamental field trapped in the QSS was 19.75 μm, which was smaller than that of the freely diffracting beam. Due to the low intensity threshold requirements for QSS formation and the sensitivity of the vidicon camera, a freely diffracting beam could not be observed at the output face of the crystal

Characterization Of Spatial Modulational Instability Of Second-Order Nonlinear Eigenmodes In A Slab Waveguide

We observed spatial modulational instabilities of nonlinear eigenmodes in a lithium niobate slab waveguide during second-harmonic generation and measured their gain

Radiation-related polarization instability of Kerr spatial vector solitons

We report the experimental observation and numerical simulations of a polarization instability of spatial vector solitons in an AlGaAs slab waveguide. At power levels where the nonlinear index change becomes comparable to the birefringence, the fast soliton becomes unstable. The instability is related to coupling of the fast soliton to the slow radiation modes through phase matching. The combined effects of bifurcation and radiation coupling are the processes ultimately limiting the stability of any single-polarization (fast and slow) Kerr soliton. © 2002 Optical Society of America.This research was supported at the Center for Research and Education in Optics and Lasers, by the National Science Foundation and a U.S. Army Research Office Mulidisciplinary University Research Initiative, at the University of Glasglow by the Engineering and Physical Science Research Council, and at the Instituto de O´ ptica of the Consejo Superior de Investigaciones Cientı´ficas by the Direccio´n General de Ensen˜anza Superior under contract BFM2000-0806. N. Akhmediev acknowledges support from the U.S. Army Research Office, Far East (grant N62649-01-1-0002).Peer Reviewe

Are Spatial Solitons Of Both Polarizations Stable In Kerr Slab Waveguides?

An overview is given on the first example of a polarization instability of spatial vector solitons. The instability is due to interaction with the radiation field rather than to the emergence of mixed polarization modes