Showing papers on "Four-wave mixing published in 1992"
TL;DR: In this article, the phase-matching characteristics of fiber four-wave mixing in the zero-dispersion wavelength region were investigated. But the results showed that the phasematching condition is satisfied and FWM light is efficiently generated at particular combinations of input light wavelengths.
Abstract: Fiber four-wave mixing (FWM) in the zero-dispersion wavelength region is described. The phase-matching characteristics are studied in the wavelength region where the first-order chromatic dispersion is zero. The results show that the phase-matching condition is satisfied and FWM light is efficiently generated at particular combinations of input light wavelengths. It is also shown that the deviation of the zero-dispersion wavelength along the fiber length plays an important role in FWM behavior. >
426 citations
TL;DR: In this article, pure C 60 was deposited on optical substrates in vacuo and spectroscopically characterized, and a small linear absorption coefficient α = 6 cm −1 was measured at 1.064 μm.
184 citations
TL;DR: In this article, a theory was developed for fiber four-wave mixing where the polarization states of input light are various and they change randomly when propagating through a fiber line, and the results show that intensity beating between the propagating lights plays an important role in four-warp mixing efficiency in a fiber.
Abstract: Four-wave mixing in a single-mode fiber is studied for general polarization states in input lights. A theory is developed for fiber four-wave mixing where the polarization states of input light are various and they change randomly when propagating through a fiber line. The results show that intensity beating between the propagating lights plays an important role in four-wave mixing efficiency in a fiber. Experimental results support the theoretical treatment. >
171 citations
TL;DR: In this article, the linear-eddy turbulent mixing model is applied to two mixing configurations in homogeneous flow: a scalar mixing layer and a two-line-source configuration, and the adjustment of a single model parameter related to the turbulence integral scale yields computed results in good agreement with a variety of measured quantities.
Abstract: The linear-eddy turbulent mixing model, formulated to capture the distinct influences of turbulent convection and molecular transport on turbulent mixing of diffusive scalars, is applied to two mixing configurations in homogeneous flow: a scalar mixing layer and a two-line-source configuration. Finite-rate second-order chemical reactions are considered, as well as the limits of fast reaction and frozen flow. Computed results are compared to measurements in a reacting-scalar mixing layer and in a two-line-source configuration involving passive-scalar mixing. For each configuration, the adjustment of a single model parameter related to the turbulence integral scale yields computed results in good agreement with a variety of measured quantities. The results are interpreted with reference to a simpler model, based solely on large-scale flapping effects, that reproduces many qualitative trends. For three-stream mixing with finite-rate chemistry, a novel dependence of the reactant correlation coefficient on the chemical reaction rate is predicted.
147 citations
TL;DR: In this article, the nonlinear gain coefficient epsilon, which induces a gain grating through the pump-probe beating, is estimated to be 1.75*10/sup -23/ m/sup 3/m/sup 4.
Abstract: Nondegenerate four-wave mixing is measured in the 1.5 mu m traveling-wave semiconductor optical amplifier medium as a function of the pump-probe detuning frequency ranging from a few GHz to 400 GHz. It is found that two different sources are responsible for the four-wave mixing: the carrier density modulation and the nonlinear gain effect. The latter is clearly observed when the detuning frequency increases above 100 GHz. The nonlinear gain coefficient epsilon , which induces a gain grating through the pump-probe beating, is estimated to be 1.75*10/sup -23/ m/sup 3/. The change in the real refractive index associated with the nonlinear gain effect, which generates an index grating, is negligibly small. The relaxation time involved in the nonlinear gain effect is found to be less than 0.3 ps. These results support the role of the spectral hole burning rather than the carrier heating in the nonlinear gain effect. >
138 citations
TL;DR: In this article, the use of phase-locked pulses in various spectroscopic techniques related to the third-order polarization P (3) is analyzed using correlation function expressions for the nonlinear response function, without alluding to any specific model for the material system.
Abstract: The use of phase-locked pulses in various spectroscopic techniques related to the third-order polarization P (3) is analyzed. Using correlation function expressions for the nonlinear response function, we clarify the interrelationship among several photon echo, pump-probe, and spontaneous light emission techniques, without alluding to any specific model for the material system. By combining phase-locked pulses and heterodyne detection it becomes possible to probe separately the real and imaginary parts of the nonlinear response function. Combining two phase-locked pulse excitation with time-resolved detection of the spontaneous light emission allows direct separation of the Raman and fluorescence contributions.
131 citations
TL;DR: Fiber four-wave mixing in transmission lines with multistage optical amplifiers is studied and it is shown that the phase-mismatching characteristic differs in Transmission lines with and without amplifiers.
Abstract: Fiber four-wave mixing in transmission lines with multistage optical amplifiers is studied. A theoretical model is described, and a fundamental experiment is carried out. It is shown that the phase-mismatching characteristic differs in transmission lines with and without amplifiers.
118 citations
TL;DR: Numerical calculations of four-wave mixing with linearly chirped pulses based on a stochastic dynamical model show that the signal near zero delay time is extremely sensitive to the presence or absence of slow fluctuations in the solute-solvent interaction.
Abstract: Ultrafast four-wave mixing experiments using chirped-pulse excitation of a dye molecule in solution are reported and analyzed. Novel time-delayed signals are observed which are assigned to coherent Stokes-Raman scattering involving the excited state. Numerical calculations of four-wave mixing with linearly chirped pulses based on a stochastic dynamical model show that the signal near zero delay time is extremely sensitive to the presence or absence of slow fluctuations in the solute-solvent interaction.
87 citations
TL;DR: It is shown that excitons dominate even when they make up only a small fraction of the excited states, and new insights into previous studies performed with spectrally broad ultrashort pulses are provided.
Abstract: We report a strong (300:1) excitonic resonance in time-resolved (100 fs) four-wave mixing in GaAs quantum wells as a function of the incident photon energy and show that it results from the large difference in the dephasing rates of excitons and free carriers. We conclude that excitons dominate even when they make up only a small fraction of the excited states. These results, in conjuction with new results in exciton-phonon scattering, provide new insights into previous studies performed with spectrally broad ultrashort pulses.
74 citations
TL;DR: In this article, the stimulated emission pumping (SEP) process was detected by means of a zero-background scheme based upon the Doppler-free technique of degenerate four-wave mixing (DFWM) spectroscopy.
Abstract: The stimulated emission pumping (SEP) process has been detected by means of a newly developed zero‐background scheme based upon the Doppler‐free technique of degenerate four‐wave mixing (DFWM) spectroscopy. Rotationally resolved SEP‐DFWM spectra recorded for the (02000) vibrational level of CS2 X 1∑+g exhibit signal‐to‐noise ratios approaching 1000:1.
71 citations
TL;DR: In this article, the degenerate four-wave mixing signal was monitored as a function of the relative arrival times for the excitation pulses, and response dynamics occurring on both femtosecond and picosecond time scales were observed for both materials.
TL;DR: Time-resolved degenerate four-wave mixing experiments were conducted on films of pure C 60 and C 70 using a picosecond tunable dye laser, and the fullerenes exhibit a large third-order optical response, and their dynamics show wavelength and fluence dependence.
Abstract: Time-resolved degenerate four-wave mixing experiments were conducted on films of pure C 60 and C 70 using a picosecond tunable dye laser. The fullerenes exhibit a large third-order optical response, and their dynamics show wavelength and fluence dependence. The temporal response is characterized by a long-lived component attributed to the triplet excited state and an early decay associated with population of the singlet excited state. This fast response is considerably shortened at higher laser fluences and an excitonic singlet-singlet annihilation mechanism is proposed
TL;DR: In this article, a simple theoretical analysis showed that the linewidth of the conjugate wave produced in four-wave mixing in semiconductor lasers is equal to the probe plus four times the LP of the pump.
Abstract: A simple theoretical analysis shows that the linewidth of the conjugate wave produced in four‐wave mixing in semiconductor lasers is equal to the linewidth of the probe plus four times the linewidth of the pump. Experimental results in good agreement with the theory are presented. This result implies an enormous enhancement in the phase noise of the conjugate wave and sets a limitation on some practical applications of four‐wave mixing.
TL;DR: In this article, the dynamics of an externally pumped phase-conjugate resonator that uses four-wave mixing in BaTiO3 is investigated experimentally, and the emergence of spatiotemporal instabilities as the degree of transverse confinement is varied by changing the Fresnel number is described in detail.
Abstract: The dynamics of an externally pumped phase-conjugate resonator that uses four-wave mixing in BaTiO3 is investigated experimentally. The emergence of spatiotemporal instabilities as the degree of transverse confinement is varied by changing the Fresnel number is described in detail. Local intensity time series show that relaxing the transverse confinement leads the system from a stationary state to periodic, then to quasi-periodic, motions and finally to chaotic behavior. In some regions of parameter space two frequencies are identified in the power spectra of the time series, indicating a route to chaos following the Ruelle–Takens–Newhouse scheme [ Commun. Math. Phys.64, 35– 40 ( 1978)]. Wave-front topological defects are identified by interferometry. As the system’s confinement is varied, the phase-defect density and the spatial correlation index are found to follow similar trends, indicating that the observed spatiotemporal dynamics may indeed be an example of defect-mediated turbulence.
TL;DR: In this paper, the influence of fiber four-wave mixing on multichannel FSK direct detection transmission is investigated and a theoretical study is presented for evaluating error rate performance when 4W mixing lights are overlapped onto a signal channel.
Abstract: The influence of fiber four-wave mixing on multichannel FSK direct detection transmission is investigated. A theoretical study is presented for evaluating error rate performance when four-wave mixing lights are overlapped onto a signal channel. Experiments are carried out to examine the theoretical treatment. Based on these results, allowable fiber input power is estimated. >
TL;DR: In this article, two different resonant four-wave mixing techniques were applied to transient molecules that are produced by laser vaporization into a supersonic expansion, and two color laser-induced grating spectroscopy (LIGS) was used to produce background-free stimulated-emission-pumping spectra of SiC2.
Abstract: We apply two different resonant four‐wave mixing techniques to transient molecules that are produced by laser vaporization into a supersonic expansion. Degenerate four‐wave mixing (DFWM) excitation spectra are obtained for C3 and SiC2 and two‐color laser‐induced grating spectroscopy (LIGS) is used to produce background‐free stimulated‐emission‐pumping spectra of SiC2.
TL;DR: Degenerate four-wave mixing in the saturable gain of a flash-lamp-pumped Nd:YAG amplifier has been investigated and multipassing the gain medium has a dramatic effect on the efficiency of the process.
Abstract: Degenerate four-wave mixing in the saturable gain of a flash-lamp-pumped Nd:YAG amplifier has been investigated. Three different geometries are examined in which the probe beam experiences (a) one pass, (b) two passes, and (c) four passes of the four-wave interaction region. It is found that multipassing the gain medium has a dramatic effect on the efficiency of the process, with a phase-conjugate reflectivity of 2500 and a conjugate energy extraction efficiency of greater than 200% demonstrated.
TL;DR: In this paper, the time dependence of the refractive index change induced in an absorbing colloidal suspension by a nanosecond laser pulse is studied by the four-wave mixing method; the behavior of the transient suggests that it is associated with an acoustic wave in the suspending fluid excited by an explosive event at the surface of the particles.
Abstract: The time dependence of the refractive index change induced in an absorbing colloidal suspension by a nanosecond laser pulse is studied by the four‐wave mixing method. A very large transient is observed even in very dilute suspensions whose amplitude oscillates on a time scale much shorter than the laser pulse duration; the effect is found in a variety of systems. The behavior of the transient suggests that it is associated with an acoustic wave in the suspending fluid excited by an explosive event at the surface of the particles. By comparing the predictions of various hydrodynamic models with the observations and by studying the effect of changing the experimental conditions on the form of the transient, it is proposed that the behavior arises from the very rapid growth of vapor bubbles around those particles which are heated sufficiently strongly; the four‐wave mixing signal monitors the coherent superposition of the resulting pressure pulses in the fluid.
TL;DR: Multiplex degenerate four-wave mixing is performed by using OH radicals in an atmospheric-pressure hydrogen-oxygen flame to determine the local instantaneous flame temperature.
Abstract: Multiplex degenerate four-wave mixing is performed by using OH radicals in an atmospheric-pressure hydrogen–oxygen flame. The ratio of the signal intensities from two OH transitions simultaneously pumped by a single laser pulse is used to determine the local instantaneous flame temperature.
TL;DR: Strong self-defocusing in bacteriorhodopsin films in the near IR with powers in the tens of milliwatts is found and the defocused beam acquires a ring pattern because of spatial self-phase modulation.
Abstract: We find strong self-defocusing in bacteriorhodopsin films in the near IR with powers in the tens of milliwatts. The defocused beam acquires a ring pattern because of spatial self-phase modulation. We also demonstrate efficient four-wave mixing with phase-conjugate reflectivities of 26%. We discuss the origin of this high nonlinearity.
TL;DR: In this paper, the results of line shape analysis, resonance light scattering and femtosecond four-wave mixing measurements are reported on several organic molecules in solution, and it is shown that a Brownian oscillator model for line broadening provides a full description for the optical dynamics in aprotic solutions.
Abstract: The results of line shape analysis, resonance light scattering and femtosecond four-wave mixing measurements are reported on several organic molecules in solution. It is shown that a Brownian oscillator model for line broadening provides a full description for the optical dynamics in aprotic solutions. The dynamics of all systems studied is found to occur in the intermediate modulation regime, where the amplitude Δ and inverse correlation time Λ of the Brownian oscillator are about equal: Δ/Λ ≈ 1. Isotopic substitution of either probe or solvent is shown to have no effect on the dynamics, from which it is concluded that the vibrational force field plays a minor role in determining the line shape. Four-wave mixing experiments with chirped femtosecond pulses yield intense coherent Raman scattering signals due to ground and excited-state vibrational coherences which are very effectively driven by the two instantaneous light fields whose frequency difference matches exactly a vibrational mode. It is shown that the “chirped” four-wave mixing signal near zero delay time only mimics the two-pulse photon echo if the system dynamics fall in the fast modulation limit: Δ/Λ⪡1. Otherwise this signal is damped not only by dephasing but also by solvation dynamics.
TL;DR: In this paper, a degenerate four-wave mixing in polymer films containing azo-based dyes is reported, and two material systems are compared, one in which the chromophores are distributed randomly in a glassy matrix, and another system in which they are chemically attached to the polymer molecules.
TL;DR: In this article, the authors describe the observation of phase conjugation at 10.6 μm in a GaAs/AlGaAs multi-quantum well-doped structure.
Abstract: We describe the observation of phase conjugation at 10.6 μm in a GaAs/AlGaAs multi‐quantum‐well‐doped structure. The responsible nonlinear susceptibility χ(3) is due to a nearly resonant intersubband transition. The magnitude of χ(3) is 7×10−5 esu and the phase conjugate reflectivity is a few tenths of a percent.
TL;DR: It is demonstrated that the saturable absorption of the inversion laser pump has a dramatic influence on the intensity dependence of the four-wave-mixing reflectivity.
Abstract: Four-wave mixing in a saturated gain medium has been modeled numerically, and the predictions for the reflectivity have been compared with experiments carried out in the laser-pumped dye Rhodamine 6G. It is demonstrated that the saturable absorption of the inversion laser pump has a dramatic influence on the intensity dependence of the four-wave-mixing reflectivity.
TL;DR: Experimental investigations of two-photon enhanced stimulated hyper-Raman and parametric four-wave-mixing emissions are described for tuning unfocused laser beams near two- photon resonance with 3D and 4D states in sodium vapor.
Abstract: Experimental investigations of two-photon enhanced stimulated hyper-Raman and parametric four-wave-mixing emissions are described for tuning unfocused laser beams near two-photon resonance with 3D and 4D states in sodium vapor. Over wide ranges of vapor pressures, path lengths, and laser power densities, the gains for stimulated hyper-Raman (SHR) scattering and for parametric four-wave mixing (PFWM) can become very greatly reduced from values expected from simple considerations. The suppression of gain can arise from interferences produced at two-photon and three-photon resonances, and from ac Stark shifts produced by internally generated near-resonant fields. Quantitative comparisons are made between observed and theoretically predicted values for SHR and PFWM production. Of 12 predicted consequences of the interferences and Stark shifting on the nonlinear behavior, ten are demonstrated through the experiments.
TL;DR: In this paper, the resonant optical nonlinearity in pseudoisocya-nine Jaggregate is investigated and it is concluded that the origin of the large optical non-linearity is mainly due to the absorption saturation of J•band.
Abstract: The resonant optical nonlinearity in pseudoisocya‐nine J‐aggregate is investigated. Large degenerate four wave mixing signals and negative absorption changes at the wavelengths corresponding to J‐aggregate absorption band are observed. It is concluded that the origin of the large optical nonlinearity is mainly due to the absorption saturation of J‐band. The mechanism of the absorption saturation is discussed on the bases of exciton delocalization effect.
TL;DR: The observed sub-Lorentzian Doppler-free line profile is fit well by existing perturbative models by using homogeneous broadening consistent with two-photon absorption measurements, and is compared with predictions from a nonperturbative two-level model.
Abstract: High-resolution degenerate four-wave mixing spectra of the R1(9) A2Σ+ → X2Π(0,0) transition of OH have been measured in a hydrogen/oxygen flame at atmospheric pressure where the Doppler and homogeneous linewidths are of comparable magnitude. The observed sub-Lorentzian Doppler-free line profile is fit well by existing perturbative models by using homogeneous broadening consistent with two-photon absorption measurements. Power broadening of the spectral profile with increasing pump-beam intensity was observed and is compared with predictions from a nonperturbative two-level model.
TL;DR: In this paper, the growth and decay of the first through fourth-order Stokes stimulated Raman scattering (SRS) are calculated as a function of the phase matching of the four-wave mixing process and the model-dependent Raman gain coefficient.
Abstract: Standard one-dimensional nonlinear-wave equations are modified to accommodate the growth and coupling of nonlinear waves in droplets. The propagation direction of the nonlinear waves along the length of an optical cell is changed so that it is along the droplet rim. The model includes radiation losses because of nonzero absorption, leakage from the droplet, and depletion in generating other nonlinear waves. For multimode-laser input, the growth and decay of the first- through fourth-order Stokes stimulated Raman scattering (SRS) are calculated as a function of the phase matching of the four-wave mixing process and the model-dependent Raman gain coefficient. The Raman gain coefficient determines the delay time of the first-order SRS, while the phase matching determines the correlated temporal profiles of the multiorder SRS. Both the Raman gain and the phase matching are found to be enhanced in the droplet. The spatial distribution of the internal input-laser intensity is calculated by using the Lorenz–Mie formalism. The temporal profile of the input-laser intensity used in the calculations is identical to the experimentally observed laser time profile. The delay time and the correlated growth and decay of nonlinear waves resulting from the numerical simulation compare favorably with those of the experimental observations. Similar calculations are made for single-mode-laser input for which the stimulated Brillouin scattering (SBS) achieves its threshold before the SRS does and subsequently pumps the SRS.
TL;DR: Degenerate four-wave mixing (DFWM) has been used to detect CO, excited through a two-photon process Intensity and pressure dependencies are presented and the potential of using the technique for flame studies is discussed as mentioned in this paper.
TL;DR: The generation of an efficient phase-conjugate wave is reported by anisotropic four-wave mixing in planar iron-doped y-cut LiNbO(3) waveguides with reflectivities of as much as 65% in the waveguide.
Abstract: We report on the generation of an efficient phase-conjugate wave by anisotropic four-wave mixing in planar iron-doped y-cut LiNbO3 waveguides. The pump waves are orthogonally polarized with respect to the signal and phase-conjugate waves. Reflectivities of the phase-conjugate signal of as much as 65% are reached in the waveguide. Experimental results are compared with numerical solutions of the corresponding system of coupled-wave equations.