Spatial Solitons in Media with Delayed-Response Optical Nonlinearities

Near-soliton scanning light-beam propagation in media with both delayed-response Kerr-type and thermal nonlinearities is analyzed. The delayed-response part of the Kerr nonlinearity is shown to be competitive as compared to the thermal nonlinearity, and relevant contributions to a distortion of the soliton form and phase can be mutually compensated. This quasi-soliton beam propagation regime keeps properties of the incli- ned self-trapped channel.Comment: 7 pages, to be published in Europhys. Let

Polarization-squeezed light formation in a medium with electronic Kerr nonlinearity

We analyze the formation of polarization-squeezed light in a medium with electronic Kerr nonlinearity. Quantum Stokes parameters are considered and the spectra of their quantum fluctuations are investigated. It is established that the frequency at which the suppression of quantum fluctuations is the greatest can be controlled by adjusting the linear phase difference between pulses. We shown that by varying the intensity or the nonlinear phase shift per photon for one pulse, one can effectively control the suppression of quantum fluctuations of the quantum Stokes parameters.Comment: final version, RevTeX, 10 pages, 5 eps figure

Transient coherent Raman scattering in the time and frequency domain

A new type of Raman spectroscopy is presented: After transient excitation of molecular modes coherently scattered Raman spectra are investigated in a depayed probing experiment. The spectral position of the Raman mode is observed after long delay times. The dephasing time is obtained from the time dependence of the scattered amplitudes. Frequency disturbing non-resonant susceptibilities are eliminated. We report on first experimental results of transient coherent Raman spectroscopy of liquid CH3CCl3

A new Raman technique of superior spectral resolution

Raman-active vibrational modes are coherently excited by the transient stimulated Raman process. A subsequent delayed probe of relatively long duration interacts with the freely relaxing vibrations. Raman spectra are generated with higher resolution and more accurate peak positions than in conventional Raman spectroscopy. In liquid cyclohexane four new Raman lines were readily detected in the frequency range 2870–2920 cm−1

Ultranarrow resonance peaks in the transmission and reflection spectra of a photonic crystal cavity with Raman gain

The Raman gain of a probe light in a three-state $\Lambda$-scheme placed into a defect of a one-dimensional photonic crystal is studied theoretically. We show that there exists a pump intensity range, where the transmission and reflection spectra of the probe field exhibit \textit{simultaneously} occurring narrow peaks (resonances) whose position is determined by the Raman resonance. Transmission and reflection coefficients can be larger than unity at pump intensities of order tens of $\mu$W/cm$^{2}$. When the pump intensity is outside this region, the peak in the transmission spectrum turns into a narrow dip. The nature of narrow resonances is attributed to a drastic dispersion of the nonlinear refractive index in the vicinity of the Raman transition, which leads to a significant reduction of the group velocity of the probe wave.Comment: 9 pages, 3 figure

Universal shape law of stochastic supercritical bifurcations: Theory and experiments

A universal law for the supercritical bifurcation shape of transverse one-dimensional (1D) systems in presence of additive noise is given. The stochastic Langevin equation of such systems is solved by using a Fokker-Planck equation leading to the expression for the most probable amplitude of the critical mode. From this universal expression, the shape of the bifurcation, its location and its evolution with the noise level are completely defined. Experimental results obtained for a 1D transverse Kerr-like slice subjected to optical feedback are in excellent agreement.Comment: 5 pages, 5 figure

Spatial Optical Solitons due to Multistep Cascading

We introduce a novel class of parametric optical solitons supported simultaneously by two second-order nonlinear cascading processes, second-harmonic generation and sum-frequency mixing. We obtain, analytically and numerically, the solutions for three-wave spatial solitons and show that the presence of an additional cascading mechanism can change dramatically the properties and stability of two-wave quadratic solitary waves.Comment: 6 pages, 4 figure

High-sensitivity imaging with multi-mode twin beams

Twin entangled beams produced by single-pass parametric down-conversion (PDC) offer the opportunity to detect weak amount of absorption with an improved sensitivity with respect to standard techniques which make use of classical light sources. We propose a differential measurement scheme which exploits the spatial quantum correlation of type II PDC to image a weak amplitude object with a sensitivity beyond the standard quantum limit imposed by shot-noise.Comment: 13 pages, 8 figure

Multistep cascading and fourth-harmonic generation

We apply the concept of multistep cascading to the problem of fourth-harmonic generation in a single quadratic crystal. We analyze a new model of parametric wave mixing and describe its stationary solutions for two- and three-color plane waves and spatial solitons. Some applications to the optical frequency division as well as the realization of the double-phase-matching processes in engineered QPM structures with phase reversal sequences are also discussed.Comment: 3 pages, 3 figure

Light dynamics in glass-vanadium dioxide nanocomposite waveguides with thermal nonlinearity

We address the propagation of laser beams in Si02-VO2 nanocomposite waveguides with thermo-optical nonlinearity. We show that the large modifications of the absorption coefficient as well as notable changes of refractive index of VO2 nanoparticles embedded into the SiO2 host media that accompany the semiconductor-to-metal phase transition may lead to optical limiting in the near-infrared wave range.Comment: 13 pages, 3 figures, to appear in Optics Letter