Soliton switching and multi-frequency generation in a nonlinear photonic crystal fiber coupler.

Soliton switching in nonlinear directional couplers implemented in photonic crystal fibers (PCF) examined here. A vector finite element method (FEM) has been developed to precisely calculate the dispersion along with coupling length of the guided modes. The PCF coupler geometry was carefully designed so that it can support soliton pulses. Soliton switching is demonstrated numerically at 1.55 microm for 100 femto-second (fs) pulses. Our theoretical results explain some of the key spectral features previously observed in the experiment.

Surface lattice solitons.

We study theoretically nonlinear surface waves in optical lattices and show that solitons can exist at the heterointerface between two different semi-infinite 1D waveguide arrays, as well as at the boundaries of a 2D nonlinear lattice. The existence and properties of these surface soliton solutions are investigated in detail.

Observation of discrete quadratic surface solitons.

We report the first observation of discrete quadratic surface solitons in self-focusing and defocusing periodically poled lithium niobate waveguide arrays. By operating on either side of the phase-matching condition and using the cascading nonlinearity, both in-phase and staggered discrete surface solitons were observed. This represents the first experimental demonstration of staggered/gap surface solitons at the interface of a semi-infinite nonlinear lattice. The experimental results were found to be in good agreement with theory.

Enhanced third-order nonlinear effects in optical AlGaAs nanowires.

We report the first observation of enhanced third-order nonlinear effects in AlGaAs nanowires. AlGaAs nanowaveguides with widths varying from 100 to 600nm were fabricated and characterized. Nonlinear phase shifts of approximately pi were experimentally observed at 1.55mum with peak powers of 30-40W in 600mum long, 550nm wide guides.

Discrete surface solitons.

It is theoretically shown that discrete nonlinear surface waves are possible in waveguide lattices. These self-trapped states are located at the edge of the array and can exist only above a certain power threshold. The excitation characteristics and stability properties of these surface waves are systematically investigated.

Discrete Talbot effect in waveguide arrays.

We report the first observation of discrete Talbot revivals in one-dimensional waveguide arrays. Unlike continuous systems where the Talbot self-imaging effect always occurs irrespective of the pattern period, in discrete configurations this process is only possible for a specific set of periodicities. Recurrence of different input periodic patterns is observed in good agreement with theory.

Highly localized discrete quadratic solitons.

We observe highly localized solitons in periodically poled lithium niobate waveguide arrays close to phase matching for second-harmonic generation. With fundamental and second-harmonic input in one channel the response indicates two distinguishable propagation schemes. Depending on the relative phase between the two input waves, a self-trapped beam emerges, resembling closely either the in- or the out-of-phase quadratic eigenmode of a single waveguide. A stable soliton propagates when the input waves are in phase.

Nonlinear optical beam interactions in waveguide arrays.

We report our investigation of Kerr nonlinear beam interactions in discrete systems. The influence of power and the relative phase between two Gaussian shaped beams was investigated in detail by performing numerical simulations of the discrete nonlinear Schrödinger equation and comparing the results with experiments done in AlGaAs waveguide arrays. Good agreement between theory and experiment was obtained.

Dissipative photonic lattice solitons.

We show that discrete dissipative optical lattice solitons are possible in waveguide array configurations that involve periodically patterned semiconductor optical amplifiers and saturable absorbers. The characteristics of these low-power soliton states are investigated, and their propagation constant eigenvalues are mapped on Floquet-Bloch band diagrams. The prospect of observing such low-power dissipative lattice solitons is discussed in detail.

One-dimensional spatial soliton families in optimally engineered quasi-phase-matched lithium niobate waveguides.

The advantage for quadratic soliton generation of engineering the quasi-phase-matching period near the input of lithium niobate slab waveguides is demonstrated. This approach allows members of one-dimensional quadratic soliton families with different values of the wave-vector mismatch to be cleanly excited and to be characterized by quantitative intensity-profile measurements of both the fundamental and the second-harmonic soliton components.

Coherent interactions of dissipative spatial solitons.

We report observation of the interaction between two coherent dissipative spatial solitons in a periodically patterned semiconductor optical amplifier with power levels of tens of milliwatts. The interactions are nonlocal and phase dependent and exhibit surprising features, such as soliton birth. The experimental results are in good agreement with the numerical simulations.

Stable dissipative solitons in semiconductor optical amplifiers.

We have observed for the first time stable spatial solitons in semiconductor optical amplifiers. Soliton destabilization due to the growth of background noise was suppressed by using patterned electrodes on the device. Numerical simulations fit very well with the experiment results. We show that it is possible to excite these solitons with about 60 mW input power.

Birth of solitons in quadratic spatial soliton collisions.

We demonstrate experimentally and theoretically the creation of a third soliton in two soliton collision processes in type I noncritically phase-matched KNbO3. The output pattern in the collision process is phase dependent, but the total energy and the relative ratio of the fundamental to the second harmonic in each soliton remain essentially unchanged to within experimental accuracy.

Observation of multiple soliton generation mediated by amplification of asymmetries.

We report the experimental observation of the formation of multiple optical quadratic solitons in a process mediated by the amplification of minute asymmetries in the diffraction properties of the input light. Experiments were conducted in phase-matched second-harmonic generation in a bulk crystal of periodically poled potassium titanyl phosphate pumped at 1064 nm. The different mechanisms that influence the process were investigated numerically, and the pulsed nature of the pump light was found to play a key role in the observed light distributions.

Existence and properties of quadratic solitons in anisotropic media: variational approach.

Stationary quadratic solitons associated with second harmonic generation in optically anisotropic media have been investigated both numerically and analytically using the variational approach. The solitons were found to have elliptical shapes, both for the fundamental and second harmonic, and their approximate beam waists and amplitudes as a function of the anisotropy and the soliton parameter were found. The important limits of anisotropic diffraction were compared to the well-known model of isotropic diffraction. The stability of anisotropic solitons was addressed via the Vakhitov-Kolokolov criterion and the regions of parameter space for which the solitons are stable were identified. Direct numerical simulations of the coupled field equations were performed to illustrate the existence, stability, and ellipticity of anisotropic quadratic solitons. In general, good agreement was found between approximate analytical approaches and numerical experiments.