Nonlinearly controlled angular momentum of soliton clusters

We demonstrate an original approach, to the best of our knowledge, to acquire nonlinear control over the angular momentum of a cluster of solitary waves. We show that the angular momentum can be adjusted by acting on the global excitation of the system. The effect is verified in liquid crystals by observing power-dependent rotation of a two-soliton cluster.     

Dispersion spectroscopy of photonic lattices

We theoretically demonstrate how to acquire the full bandgap spectrum of a photonic lattice of arbitrary profile. Focusing on the 1D case in the presence of a linear refractive index acceleration and employing a multiscale analysis, we show that each photonic band can be directly mapped by the light evolution in the lattice, whereas the size of each gap corresponds to the tunneling rate. We verify the analytical results with numerical simulations and discuss experimental realizations of this technique for dispersive spectroscopy.     

Parametric solitons in two-dimensional lattices of purely nonlinear origin

We demonstrate spatial solitons via twin-beam second-harmonic generation in hexagonal lattices realized by poling lithium niobate planar waveguides. These simultons can be steered by acting on power, direction, and wavelength of the fundamental frequency input.     

All-optical isolation by directional coupling

A nonlinear phase defect inserted in a coherent coupler can realize an effective all-optical diode. Basic features, design criteria, and suggested implementations are discussed with reference to Kerr-like media.     

Comments on “Breather-like director reorientations in a nematic liquid crystal with nonlocal nonlinearity” by L. Kavitha,M. Venkatesh and D. Gopi

We point out a mistake that the authors of Kavitha et al. (2013) incurred by overlooking the physical meaning of their mathematical derivation. By doing this, we hope to emphasise the importance of an awareness of the strict links which mathematical models need to maintain with physical phenomena and systems.     

Terahertz pulse generation via optical rectification in photonic crystal microcavities

Using a three-dimensional fully vectorial nonlinear time-domain analysis, we numerically investigate generation of terahertz radiation by pumping a photonic crystal microcavity out of resonance. High quality factors and a quadratic susceptibility lead to few-cycle terahertz pulses via optical rectification. Material dispersion as well as linear and nonlinear anisotropy is fully accounted for.     

Phase- and polarization-insensitive all-optical switching by self-guiding in quadratic media

We demonstrate numerically that a frequency-degenerate process through typeII downconversion in a quadratic nonlinear waveguide leads to the formation of spatial simultons and all-optical switching in the presence of a control signal. This novel effect is phase independent, generally insensitive to polarization, and weakly affected by the magnitude of the control input. Multiple solitary waves can also be obtained, depending on the details of the interaction.     

Nematicon waveguides: self-confined beams and their electric control

We investigate the excitation and propagation of self-confined beams and the electric steering of soliton-based optical waveguides in nematic liquid crystalline planar cells. Controlled addressing of a signal is achieved in space by exploiting the electro-optic response of the uniaxial material, employing either uniform or patterned electrodes to alter either the Poynting vector or the wavevector, respectively.     

Transient-mode excitation, terahertz generation and wavelength shifting in a photonic band gap

Dynamic responses of photonic crystal microcavities in nonlinear media are analyzed via both a finite-difference code and coupled-mode theory in the time domain. Optical frequency generation in both second- and third-order nonlinear materials is demonstrated based on the transient evolution of cavity modes. Terahertz waves can be generated in quadratically nonlinear crystals by optical rectification, whereas state generation inside the band gap can be linked to a Rabi-like splitting in cubic media. An all-optical ultra-fast wavelength shifter is proposed.     

Nonparaxial (1 + 1)D spatial solitons in uniaxial media

We investigate nonparaxial spatial solitons in uniaxial media with a cubic nonlinearity, accounting for the fully vectorial electromagnetic perturbation and the longitudinal field component in the self-induced index well. We discuss the effective nonlocality arising in purely Kerr media and soliton self-steering owing to nonlinear changes in walk-off.