Yoohong Min

Integrated Optical Devices in Lithium Niobate

Lithium niobate offers incredible versatility as a substrate for integrated optics. Researchers have developed an array of new optical devices based on this material, including waveguide structures, electro-optical wavelength filters and polarization controllers, lasers with remarkable properties, nonlinear frequency converters of exceptional efficiency, ultrafast all-optical signal processing devices and single photon sources.

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.

Wavelength- and time-selective all-optical channel dropping in periodically poled Ti:LiNbO 3 channel waveguides

Wavelength- and time-selective channel dropping by sum frequency generation of a 10-GHz channel out of a 4 /spl times/ 10 GHz optical time-division-multiplexed signal has been demonstrated using two fully packaged Ti : PPLN wavelength converters. Less than -15 dB of channel dropping extinction ratio is observed with average (peak) coupled pump power of 100 mW (2 W).

OBSERVATION OF ONE- AND TWO-DIMENSIONAL DISCRETE SURFACE SPATIAL SOLITONS

The recent theoretical predictions and experimental observations of discrete surface solitons propagating along the interface between a one- or two-dimensional continuous medium and a one- or two-dimensional waveguide array are reviewed. These discrete solitons were found in second order (periodically poled lithium niobate) and third order nonlinear media, including AlGaAs, photorefractive media and glass, respectively.

Spatial trapping of short pulses in Ti-indiffused LiNbO(3) waveguides.

We show numerically and experimentally that spatial trapping can be induced in quadratic media even if the pump pulses duration is shorter than the group-delay mismatch between fundamental wave and second-harmonic components. The influence of phase mismatch and pulse power on the trapping effect is discussed. Spatial, temporal, and spectral behaviors that accompany self-trapped propagation are highlighted.

Spatial ultrafast switching and frequency conversion in lithium niobate waveguide arrays

We demonstrate phase-insensitive, ultrafast, all-optical spatial switching and frequency conversion in quadratically nonlinear waveguide arrays in periodically poled lithium niobate. Routing of milliwatt signals with wavelengths in the communication band (1550 nm) is achieved without pulse distortions by parametric interaction with a control beam with 10-W power and wavelengths near 775 nm.

Soliton emission at a phase-mismatch boundary in a quadratic nonlinear film waveguide

We report the experimental demonstration of spatial nonlinear beam displacement caused by an interface between periodically modulated and uniform quadratic nonlinearity. We observe intensity- and phase-mismatch-dependent spatial beam displacement at 1548 nm in lithium niobate waveguides. The device has the potential to provide a soliton-emission-based, ultrafast all-optical switch.

Discrete modulational instability in periodically poled lithium niobate waveguide arrays

Parametric gain associated with discrete modulational instability due to the second order nonlinearity chi(2)(-2omega;omega,omega) was investigated experimentally in periodically poled lithium niobate arrays of weakly coupled channel waveguides for conditions of both positive and negative phase-mismatch for second harmonic generation.

Generation of quadratic spatially trapped beams with short pulsed light

We report a numerical and experimental investigation on the generation of spatial self-narrowed beams with short temporal pulsed excitation in quadratic film waveguides. The impact of temporal group-velocity mismatch between the quadratic multiple interacting signals is shown. We accurately studied the spatial, temporal and spectral signals dynamics versus pulse power and phase mismatch. We show that spatial self-trapping can be induced even if the pump pulse duration is significantly shorter than the group delay mismatch between interacting waves for large enough positive phase mismatches.

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.