Enhancement of third-harmonic generation in nonlocal spatial solitons

We report on the observation of Type I third-harmonic generation induced by a train of femtosecond laser pulses in nematic liquid crystals. We find that as the average power of the train is increased, the frequency conversion process is enhanced as a consequence of the tight confinement of the pulses into a nonlocal spatial soliton.     

Discrete propagation and spatial solitons in nematic liquid crystals

We investigate, for the first time to our knowledge, the discrete propagation of near-infrared light in a voltage-controlled array of channel waveguides in undoped nematic liquid crystals under planar anchoring conditions. This novel geometry enables us to drive the system from one-dimensional bulk diffraction to discrete propagation and, for larger excitations, to discrete spatial solitons, or nematicons. The observed phenomena are adequately described by a scalar model that encompasses the voltage-dependent reorientational response of the material.     

Low-threshold spatial solitons in reverse-proton-exchanged periodically poled lithium niobate waveguides

Combining reverse proton exchange and uniform periodic poling in LiNbO3 planar waveguides, we demonstrate low-energy spatial optical solitons by second-harmonic generation at room temperature, with a threshold as low as 23 pJ/microm at 1.5 microm.     

Observation of optical spatial solitons in a highly nonlocal medium

We report on the observation and quantitative assessment of self-trapped pulsating beams in a highly nonlocal nonlinear regime. The experiments were conducted in nematic liquid crystals and allow a meaningful comparison with the prediction of a scalar theory in the perturbative limit, while addressing the need for beyond-paraxial analytical treatments.     

Intensity-controlled interactions between vectorial spatial solitary waves in quadratic nonlinear media

We numerically investigate the interaction of vectorial solitary waves propagating in a bulk crystal with a phase-matchable quadratic nonlinearity. We obtain coalescence, steering, crossing, or repulsion by controlling the launched intensities in two orthogonal polarizations without any coherent seed at the second harmonic.     

Compensating group-velocity mismatch in parametric frequency generation

We propose and numerically investigate a simple scheme based on frequency-selective mirrors for compensating group-velocity mismatch during harmonic generation. We address the case of frequency doubling and illustrate the effectiveness of the approach for multipass frequency doubling in LiNbO(3).     

Nonlinear bouncing of nonlocal spatial solitons at the boundaries

We investigate, both experimentally and theoretically, the interaction of (2D+1) spatial solitons with the boundaries of a nonlinear medium in the presence of nonlocality. We demonstrate power-dependent nonlinear repulsion at the boundaries, in quantitative agreement with the model predictions.     

Bloch function approach for parametric gap solitons

Using a Bloch function approach, we predict the existence of parametric gap solitary waves in a grating structure with quadratic nonlinearity. These waves consist of mutually trapped envelopes at the fundamental frequency and at the second harmonic, which are not sustained by any equivalent cubic nonlinearity.     

Mode interplay via quadratic cascading in a lithium niobate waveguide for all-optical processing

The effects of the nonlinear interplay between modes of a lithium niobate channel waveguide are numerically investigated. Based on the nonlinear phase-shift obtainable via up- and down-conversion of each mode at the input frequency into and from the second-harmonic modes generated through Type I and Type II interactions, the waveguide can operate as an all-optical transistor with large small-signal-gain, and as a mode-mixing device capable of spatial switching and routing. It exhibits good switching contrast at 1.55 m with low driving powers.     

Light induced angular steering via Floquet-Bloch band-tunnelling in one-dimensional liquid crystalline photonic lattices

We investigate all-optical Zener tunnelling in electro-optically tunable arrays of identical channel waveguides in undoped nematic liquid crystals. By all-optically inducing a refractive acceleration, we demonstrate a novel technique for band-to-band tunnelling, as well as a novel approach to light controlled steering and readdressing.