Multipole spatial vector solitons

We introduce the concept of multipole spatial optical vector solitons associated with higher-order guided modes trapped by a soliton-induced waveguide in a bulk medium. Such stationary localized waves include previously predicted vortex- and dipole-mode vector solitons and also describe new higher-order vector solitons and necklace-type beams. We present the theoretical and experimental results of the structure, formation, and instability development of the quadrupole vector solitons.

Generation of 5-fs pulses and octave-spanning spectra directly from a Ti:sapphire laser

Spectra extending from 600 to 1200 nm have been generated from a Kerr-lens mode-locked Ti:sapphire laser producing 5-fs pulses. Specially designed double-chirped mirror pairs provide broadband controlled dispersion, and a second intracavity focus in a glass plate provides additional spectral broadening. These spectra are to our knowledge the broadest ever generated directly from a laser oscillator.

Observation of dipole-mode vector solitons

We report on the first experimental observation of a novel type of optical vector soliton, a dipole-mode soliton, recently predicted theoretically. We show that these vector solitons can be generated in a photorefractive medium employing two different processes: a phase imprinting, and a symmetry-breaking instability of a vortex-mode vector soliton. The experimental results display remarkable agreement with the theory, and confirm the robust nature of these radially asymmetric two-component solitary waves.

Analytical solution for photorefractive screening solitons

We study formation and interaction of one-dimensional screening solitons in a photorefractive medium with sublinear dependence of the photoconductivity on light intensity. We find an exact analytical solution to the corresponding nonlinear Schrodinger equation. We show that these solitons are stable in propagation and their interaction is generic for solitons of saturable nonlinearity. In particular, they may fuse or "give birth" to new solitons upon collision.

Vortex-stripe soliton interactions

We study the interaction of an optical vortex soliton with a dark-soliton stripe in a bulk nonlinear defocusing medium. We develop a multiscale asymptotic theory to predict the main effect of the interaction and then study it experimentally, observing vortex-induced stripe bending, development of the transverse instability, and stripe breakup.

Saturable absorption in poly(indenofluorene): a picket-fence polymer

Poly(indenofluorene) shows a strong degenerate four-wave mixing (DFWM) response when it is excited with 100-fs pulses at 800 nm. The DFWM signal scales with the 1.5 power of the input intensity, which we interpret as being due to absorption saturation phenomena. The saturation was studied by open-aperture Z scan in dilute solutions of poly(indenofluorene) in chloroform. The changes in the absorption coefficient alpha are described by the formula alpha = alpha(0)/[1 + (I/I(sat))(1/2)], where I(sat) is the saturation intensity, which is found to be of the order of 100>MW/cm(2).

Ultrashort pulses generated by mode-locked lasers with either a slow or a fast saturable-absorber response

We present a new exact solution for ultrashort pulses generated by passively mode-locked lasers, taking into account the slow and the fast parts of the semiconductor saturable-absorber response in the nonsaturated limit.

Annihilation of photorefractive solitons

We investigate experimentally the interaction of two-dimensional solitary beams in photorefractive strontium barium niobate crystal. We show that simultaneous collision of many solitons can result in complete annihilation of some of them. This effect depends on the relative phases of the solitons and may be useful for application in the formation of multiport waveguide junctions.

Vortex soliton motion and steering

Experimental demonstration of the steering of an optical vortex soliton by the superposition of a weak coherent background field is presented. A model to account for vortex motion is derived, and its validity is verified experimentally and numerically.

Observation of vortex solitons created by the instability of dark soliton stripes

The first experimental observation to the authors' knowledge is reported of the generation of optical vortex solitons from instability and breakup of a dark soliton stripe propagating through a saturable self-defocusing nonlinear medium.

Multimode structure of bright and dark vector solitons in photorefractive media

We study coupled solitary waves in a photorefractive medium. For a special orientation of a cubic photorefractive crystal, stationary wave propagation in the form of coupled dark and bright solitons is possible. We classify these solutions and study their stability, using numerical simulations.

Tuning the properties of poly(p-phenylenevinylene) for use in all-optical switching

We show that, as the conjugation length of poly(p-phenylenevinylene) increases, the ratio of its two-photon absorption coeff icient to third-order nonlinearity at 800 nm decreases, rendering the material suitable for alloptical switching.

Wave mixing and beam profile control in a photorefractive waveguide

Photorefractive wave mixing in a waveguide geometry with nonguided external pumps has been studied experimentally and theoretically. Guided beam amplification has been obtained in an iron-doped lithium niobate waveguide. Additionally, photorefractive grating couplers that allow the transverse profile of the decoupled guided beam to be controlled are demonstrated.

Is two-photon absorption a limitation to dark soliton switching?

It is shown that two-photon absorption does not always place a fundamental limitation on soliton devices: The steering angle, the key characteristic of switching devices based on the propagation of dark spatial solitons, is almost preserved as the intensity of the background wave decays in the presence of weak two-photon absorption.

Steerable optical waveguides formed in self-defocusing media by using dark spatial solitons

We demonstrate that steerable, two-dimensional, single-mode optical waveguides can be formed in defocusing media by exciting dark spatial solitons.