Russell Fuerst

All‐optical switching by spatial walkoff compensation and solitary‐wave locking

We demonstrate a novel approach to phase insensitive, all‐optical steering and switching based on an intensity‐induced change in the propagation direction of multidimensional spatial solitary waves in bulk, birefringent, quadratic nonlinear media. Our demonstration is based on second‐harmonic generation in a KTP crystal. Compensation for the lateral displacements due to walkoff in SHG is observed.

QUADRATIC SPATIAL SOLITON GENERATION BY SEEDED DOWNCONVERSION OF A STRONG HARMONIC PUMP BEAM

Two-dimensional quadratic spatial solitons were generated experimentally near phase-matching conditions for type II frequency doubling in KTP by the seeding of a strong second-harmonic field with a weak input at the fundamental wavelength. The self-trapped beams were shown to be insensitive to the energy, phase, and polarization of the fundamental-frequency seed input beam.

Beam reshaping by use of spatial solitons in the quadratic nonlinear medium KTP.

We have demonstrated the transformation of elliptical beams into cylindrically symmetric beams through the formation of quadratic spatial solitons. By use of type II phase-matched second-harmonic generation in a KTP crystal, input elliptical beams with aspect ratios as large as 8:1 were propagated through the KTP crystal, and they exited the crystal as a cylindrically symmetric beam. The threshold for soliton formation and the power throughput were measured versus ellipticity.

Two-dimensional type I quadratic spatial solitons in KNbO 3 near noncritical phase matching

Experiments on the properties of quadratic, two-dimensional spatial soliton properties in KNbO(3) near and at noncritical phase matching (NCPM) are reported. The NCPM geometry leads to unique features such as a large angular bandwidth for soliton generation, weak dependence of soliton composition on intensity and incidence angle, and unique multisoliton-generation properties.

Toward soliton emission in asymmetric GaAs/AlGaAs multiple-quantum-well waveguide structures below the half-bandgap.

We report what is to our knowledge the first experimental evidence of nonlinear beam displacement in a strip-loaded GaAs/AlGaAs multiple-quantum-well waveguide with an asymmetric, nonlinear cladding. An intensity-dependent spatial displacement of ~2 mum was observed for the guided mode at a wavelength of 1.55 mum. Numerical simulations that correspond to the experiment are also presented. The device has the potential of providing a soliton-emission-based, ultrafast all-optical switch.

Properties of type II quadratic solitons excited by imbalanced fundamental waves.

It was shown experimentally for type II second-harmonic generation in KTP that the family of quadratic spatial solitons exists over a wide range of imbalances for the two fundamental wave inputs. The threshold for soliton formation was measured as a function of both phase mismatch and relative input fraction of the energy in the two fundamental polarizations. Launching unequal fundamental inputs led to an imbalanced three-coupled-field output composition.

Robust generation, properties and potential applications of quadratic spatial solitons generated by optical parametric amplification

Quadratic spatial solitary waves are predicted and observed experimentally near degeneracy for Type II optical parametric amplification in bulk KTP, by seeding an intense pump optical field with a control signal at half the pump wave frequency. The self-trapping of light at the two wavelengths has been shown to be insensitive to phase, polarization and magnitude of the control input, and can be exploited in novel schemes for robust all-optical processing.

Quadratic spatial soliton generation by seeded down conversion of a strong pump beam

Quadratic spatial solitons have been generated during second-harmonic generation under easy-to-achieve conditions and should be pervasive in other second-order nonlinear interactions. One of the more interesting cases is the downconversion process, which is the essence of parametric generators and oscillators. In this investigation, we report on the generation of two-dimensional quadratic spatial solitons (QSS) in a KTP crystal near the degeneracy point for the parametric interaction, i.e., the reverse second-harmonic generation. Here we report on the observation of such solitons in a l-cm-long KTiOPO/sub 4/ crystal where the extraordinarily polarized harmonic field interacts with two fundamental fields with both ordinary and extraordinary components.

Observation of two-dimensional quadratic spatial-solitons in type I potassium niobate

This current work demonstrates these quadratic spatial solitons (QSSs) in a type I phase matched second harmonic configuration in potassium niobate (KNbO/sub 3/), reducing the system to a two-wave interaction between singular second harmonic and fundamental wave fields.

Experiments on Quadratic Spatial Solitons

Spatial solitons are beams which do not diffract on propagation in a material due to the presence of some optical nonlinearity. Their properties were first documented by John Scott Russell when he reported his observations on non-spreading water waves which consisted of a single “hump” propagating in a canal in Scotland.[l] In the very early days of nonlinear optics, interest was quickly evoked by what were then called “self-focused filaments”, initiated by observations of self-focusing of powerful lasers in optical media, frequently leading to stable filaments or even material damage. [2,3] However it was not until the late 1990s that systematic experimental research into spatial solitons was initiated. [4] Since then there has been a surge of activity and many new solitons have been observed. [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]