Elliptic incoherent solitons in saturable nonlinear media

We identify elliptic incoherent spatial solitons in isotropic saturable nonlinear media. These solitary states are possible, provided that their correlation function is anisotropic. The propagation dynamics of this new class of solitons are investigated by use of numerical simulations. We find that, during a collision event of two such elliptic solitons, their intensity ellipse rotates, and at the same time their centers of gravity tend to revolve around each other.     

Anisotropic enhancement of discrete diffraction and formation of two-dimensional discrete-soliton trains

We demonstrate anisotropic enhancement of discrete diffraction and formation of discrete-soliton trains in an optically induced photonic lattice. Such discrete behavior of light propagation was observed when a one-dimensional stripe beam was launched appropriately into a two-dimensional lattice created with partially coherent light. Our experimental results are corroborated with numerical simulations.     

Transmission of images through highly nonlinear media by gradient-index lenses formed by incoherent solitons

We experimentally demonstrate image transmission through a noninstantaneous self-focusing medium. A partially spatially incoherent soliton is used to form a multimode waveguide in a photorefractive crystal, and the modes of that waveguide are used to transmit an incoherent image through this nonlinear medium.     

Design of switching junctions for two-dimensional discrete soliton networks

The performance of switching junctions in two-dimensional discrete-soliton networks is analyzed theoretically by coupled-mode theory. Our analysis can be used for the design of routing junctions with specified operational characteristics. Appropriately engineering the intersection site can further improve the switching efficiency of these junctions. Our analytical results are verified by numerical simulations.     

SINGLET OXYGEN INDUCES FRANK STRAND BREAKS AS WELL AS ALKALI- AND PIPERIDINE-LABILE SITES IN SUPERCOILED PLASMID DNA

A covalently closed, circular, supercoiled plasmid was exposed to singlet oxygen by a separated-surface sensitizer. For each exposure, the quantity of single oxygen entering the DNA target solution was estimated by its oxidation of histidine. After singlet oxygen exposure, some DNA samples were treated to disclose occult lesions. Agarose gel electrophoresis was then used to resolve the unrelaxed supercoils from the relaxed circular and linear species, and all bands were quantitated fluorometrically. Exposure of supercoiled plasmid DNA to singlet oxygen induced frank DNA strand breaks, alkali-labile sites (pH 12.5, 90 degrees C, 30 min), and piperidine-labile sites (0.4 M, 60 degrees C, 30 min), all in a dose-dependent manner. Yields of alkali-labile and piperidine-labile sites ranged from one to four times the frank strand break yield. Replacement of buffered H2O by buffered D2O as the DNA solvent for singlet oxygen exposures increased DNA lesion yields by a factor of 2.6 (averaged over lesion classes). Our data for the detection of frank strand breaks is at variance with published results from studies in which singlet oxygen was derived from a thermolabile endoperoxide dissolved in the DNA solution.     

Minimizing bending losses in two-dimensional discrete soliton networks

We show that reflection losses suffered by discrete solitons along sharp bends in two-dimensional waveguide-array networks can be almost eliminated. Analysis indicates that this can be accomplished by appropriately engineering the corner site of the bend. Our analytical results are verified by numerical simulations.     

Self-trapping and flipping of double-charged vortices in optically induced photonic lattices

We report what is believed to be the first observation of self-trapping and charge-flipping of double-charged optical vortices in two-dimensional photonic lattices. Both on- and off-site excitations lead to the formation of rotating quasi-vortex solitons, reversing the topological charges and the direction of rotation through a quadrupole-like transition state. Experimental results are corroborated with numerical simulations.     

Discrete solitons and soliton-induced dislocations in partially coherent photonic lattices

We investigate both experimentally and theoretically the interaction between a light beam and a photonic lattice optically induced with partially coherent light. We demonstrate a clear transition from two-dimensional discrete diffraction to discrete solitons in such a partially coherent lattice and show that the nonlinear interaction process is associated with a host of new phenomena including lattice dislocation, lattice deformation, and creation of structures akin to optical polarons.     

T-scanner for measuring pulse durations

A method for ultrashort pulse-duration measurement is analysed both theoretically and experimentally. The approach is based on a time-resolved induced phase modulation of a probe beam-pulse in a two-colour Z-scan configuration. The experimental results presented are in good agreement with the simple analytical result derived for retrieving unknown pulse width.