Stefan Wabnitz

Self-induced transparency solitons in nonlinear refractive periodic media

Abstract We obtain new nonstationary soliton-like solutions for an extended version of the classical massive Thirring model which, in nonlinear optics, describes Bragg-resonant wave propagation in a periodic Kerr medium. These solitons represent intense optical wavetrains whose envelope travels unchanged through a distributed feedback reflection filter, in spite of the fact that the mean wavelength of the soliton is in the center of the forbidden gap. The soliton group velocity may be anywhere between zero and the speed of light in the medium.

Soliton switching in fiber nonlinear directional couplers

We predict all-optical switching of solitons between the two linear modes of a nonlinear coherent coupler made from a dual-core fiber operating in the anomalous dispersion regime.

Solutions of the vector nonlinear Schrödinger equations: evidence for deterministic rogue waves.

We construct and discuss a semi-rational, multi-parametric vector solution of coupled nonlinear Schrödinger equations (Manakov system). This family of solutions includes known vector Peregrine solutions, bright-dark-rogue solutions, and novel vector unusual freak waves. The vector freak (or rogue) waves could be of great interest in a variety of complex systems, from optics to Bose-Einstein condensates and finance.

Second-harmonic generation in silicon waveguides strained by silicon nitride

Silicon photonics meets the electronics requirement of increased speed and bandwidth with on-chip optical networks. All-optical data management requires nonlinear silicon photonics. In silicon only third-order optical nonlinearities are present owing to its crystalline inversion symmetry. Introducing a second-order nonlinearity into silicon photonics by proper material engineering would be highly desirable. It would enable devices for wideband wavelength conversion operating at relatively low optical powers. Here we show that a sizeable second-order nonlinearity at optical wavelengths is induced in a silicon waveguide by using a stressing silicon nitride overlayer. We carried out second-harmonic-generation experiments and first-principle calculations, which both yield large values of strain-induced bulk second-order nonlinear susceptibility, up to 40 pm V(-1) at 2,300 nm. We envisage that nonlinear strained silicon could provide a competing platform for a new class of integrated light sources spanning the near- to mid-infrared spectrum from 1.2 to 10 μm.

Experimental observation of polarization instability in a birefringent optical fiber

We present the first experimental demonstration of spatial instability in the nonlinear evolution of the state of polarization of an intense light beam in a birefringent Kerr‐like medium. As the peak power crosses the threshold for the instability, we observed strong intensity‐dependent power transfer between the two counter‐rotating circularly polarized waves propagating along a birefringent optical fiber. The experimental results agree well with the theory.

Stability analysis of nonlinear coherent coupling

We analyze the nonlinear coupled differential equations for the nonlinear coherent coupler by extending the Stokes parameters formalism. The existence of bifurcation and instability phenomena is proved.

Dissipative modulation instability in a nonlinear dispersive ring cavity

Abstract We investigate the modulational instability in a synchronously pumped nonlinear dispersive ring cavity. The infinite-dimensional Ikeda map which describes the evolution of the field in the cavity is reduced to a partial derivative equation which allows for analytical developments. We show that, owing to the dissipative nature of the problem, the physics of modulational instability in the ring is fundamentally different from the usual modulational instability in a nonlinear dispersive fiber. In particular, we predict the formation of stable temporal dissipative structures for both the normal and the anomalous dispersion regime of the fiber.

Optical solitary waves induced by cross-phase modulation.

We show that an optical pulse can propagate undistorted as a bright solitary wave in the normal dispersion regime when it couples through cross-phase modulation to a dark pulse in the anomalous dispersion regime.

Beneficial impact of wave-breaking for coherent continuum formation in normally dispersive nonlinear fibers

We study the evolution of a pulse propagating in a normally dispersive fiber in the presence of Kerr nonlinearity. We review the temporal and spectral impact of optical wave-breaking in the development of a continuum. The impact of linear losses or gain is also investigated.

Nonlinear nonreciprocity in a coherent mismatched directional coupler

The analytical solution is given for the nonlinear propagation in a linearly mismatched directional coupler taking into account an arbitrary nonuniform nonlinearity. The effect of mismatching which causes nonreciprocal nonlinear switching of the device is analyzed in detail.