Showing papers on "Four-wave mixing published in 1999"
TL;DR: In this paper, the mixing quality of a single mixing unit and mixer arrays having various designs was characterized and a known test reaction for mixing quality had to be optimized, since a much higher sensitivity as for the characterization of macroscopic mixers was needed.
Abstract: The mixing quality of a single mixing unit and mixer arrays having various designs was characterized. A known test reaction for mixing quality had to be optimized, since a much higher sensitivity as for the characterization of macroscopic mixers was needed. This adapted test reaction allowed not only the characterization of the mixing quality but also analysis of the homogeneity of the flow distribution between parallely aligned mixing units. A comparison of the mixing quality to those of macroscopic reference systems (like mixing in stirred and unstirred vessels as well as to laminar and turbulent mixing-tees) is presented. The mixing quality−volume flow dependence revealed a complex behavior, the hydrodynamic origin of which has been analyzed.
366 citations
TL;DR: In this article, a coherent four-wave mixing in which three sodium matter waves of differing momenta mix to produce, by means of nonlinear atom-atom interactions, a fourth wave with new momentum is presented.
Abstract: The advent of the laser as an intense source of coherent light gave rise to nonlinear optics, which now plays an important role in many areas of science and technology. One of the first applications of nonlinear optics was the multi-wave mixing1,2 of several optical fields in a nonlinear medium (one in which the refractive index depends on the intensity of the field) to produce coherent light of a new frequency. The recent experimental realization of the matter-wave ‘laser’3,4—based on the extraction of coherent atoms from a Bose–Einstein condensate5—opens the way for analogous experiments with intense sources of matter waves: nonlinear atom optics6. Here we report coherent four-wave mixing in which three sodium matter waves of differing momenta mix to produce, by means of nonlinear atom–atom interactions, a fourth wave with new momentum. We find a clear signature of a four-wave mixing process in the dependence of the generated matter wave on the densities of the input waves. Our results may ultimately facilitate the production and investigation of quantum correlations between matter waves.
337 citations
TL;DR: In this paper, a comprehensive numerical and experimental study of 40 Gbit/s RZ transmission is presented which reveals two new forms of nonlinear interactions that limit the speed of high-speed systems.
Abstract: A comprehensive numerical and experimental study of 40 Gbit/s RZ transmission is presented which reveals two new forms of nonlinear interactions that limit the speed of high-speed systems. Both limitations originate from nonlinear interactions among neighbouring bits. The first interaction involves cross-phase modulation and leads to timing fluctuations while the second interaction originates from four-wave mixing and leads to the creation of shadow pulses.
279 citations
TL;DR: In this article, strong overlap of adjacent pulses in dispersion-managed return-to-zero transmission was shown to reduce pulse-topulse interaction and timing jitter, and the limiting factors for this pulse-overlapped transmission were the amplitude fluctuations and the ghost pulse generation induced by four-wave mixing between spectral components within a single channel.
Abstract: We show that strong overlap of adjacent pulses in dispersion-managed return-to-zero transmission reduces pulse-to-pulse interaction and timing jitter. The limiting factors for this pulse-overlapped transmission are the amplitude fluctuations and the ghost pulse generation induced by four-wave mixing between spectral components within a single channel.
231 citations
TL;DR: In this paper, a new phase-matching factor is derived for four-wave mixing (FWM) that includes the effects of self-phase and cross-phase modulation in optical fibers.
Abstract: A new phase-matching factor is derived for four-wave mixing (FWM) that includes the effects of self-phase and cross-phase modulation in optical fibers. Theoretical results predict that the wavelength of peak FWM efficiency shifts away from the fiber zero-dispersion wavelength and indicate that the conventional phase-matching factor may induce significant errors in FWM calculations. Experiments are presented to verify the new phase-matching factor and the related theoretical results. The measured results agree well with those predicted by the new phase-matching factor.
139 citations
TL;DR: In this article, the statistics of the eye-closure due to four-wave mixing (FWM) in the presence of arbitrary data values and optical phases in all WDM channels were evaluated.
Abstract: For wavelength division multiplexing (WDM) systems over nonzero dispersion fiber, we evaluate the statistics of the eye-closure due to four-wave mixing (FWM) in the presence of arbitrary data values and optical phases in all WDM channels. By Monte Carlo (MC) experiments, we determine the distribution function and the standard deviation of the eye-closure for several channel counts. Convolution of the distribution after a single span yields the eye-closure distribution after multiple amplified spans. The results are used to assess the Q-factor penalty in a WDM system. The limits for optical power, chromatic dispersion and channel spacing can then be found. It is shown that the power of the FWM products can be used to estimate the system penalty due to FWM. When comparing standard single-mode fiber with nonzero dispersion-shifted fiber (NZDSF), we find that standard fiber allows for a triple narrower channel spacing than NZDSF, given the same set of system parameters.
94 citations
TL;DR: In this paper, the authors measured the third order susceptibility for doubly vibrationally enhanced four wave mixing in the model system, acetonitrile, and showed that two resonances multiplicatively increase the mixing efficiency if there is mode coupling and provide an additional spectral dimension for vibrational spectroscopy.
Abstract: We report the measurement of the third order susceptibility ${\ensuremath{\chi}}^{(3)}$ for doubly vibrationally enhanced four wave mixing in the model system, acetonitrile. Two resonances multiplicatively increase the mixing efficiency if there is mode coupling and provide an additional spectral dimension for vibrational spectroscopy that greatly improves its resolution. Such methods promise to have important applications for vibrational spectroscopy of complex materials.
87 citations
TL;DR: In this article, the authors use acetonitrile in different mixtures as a model system to demonstrate the spectral selectivity that allows DOVE methods to remove the spectral congestion from vibrational spectra of complex mixtures and to discriminate against a strong water background.
Abstract: A new form of vibrational spectroscopy has recently been demonstrated using three coherent sources to generate nonlinear four wave mixing (FWM). It is an optical analogue of 2D NMR. The four transitions that occur in FWM include combinations of infrared absorption and Raman transitions and result in doubly vibrationally enhanced (DOVE) four wave mixing (FWM). In this paper, we use acetonitrile in different mixtures as a model system to demonstrate the spectral selectivity that allows DOVE methods to remove the spectral congestion from vibrational spectra of complex mixtures and to discriminate against a strong water background. The selectivity results from two multiplicative vibrational enhancements and the intra- and intermolecular interactions that cause mode coupling. Since DOVE features cannot occur in the absence of mode coupling, these methods isolate the spectral features that are associated with interactions. This method promises to have important applications for probing complex biological, chemi...
86 citations
TL;DR: In this article, a new detection scheme for pump-probe and four-wave mixing heterodyne experiments, using balanced detection and a dual-phase lock-in for spectral filtering, was demonstrated on an InGaAsP/InP bulk optical amplifier.
79 citations
01 Sep 1999
TL;DR: It is shown that strong overlap of adjacent pulses in dispersion-managed return-to-zero transmission reduces pulse- to-pulse interaction and timing jitter.
Abstract: Nonlinear pulse-to-pulse interaction is one of the main limiting factors in high-bit-rate transmission systems.
69 citations
TL;DR: In this article, a broad-band all-optical switch that exhibits high linearity (>30 dB), high switching contrast (>25 dB), and large data wavelength tunability (100 nm) is presented.
Abstract: We report on a broad-band all-optical switch that exhibits high linearity (>30 dB), high switching contrast (>25 dB), and large data wavelength tunability (100 nm). The switching principle is based on four-wave mixing. Two control pulse trains are placed in the gain wavelength region of a 1300-nm semiconductor-optical amplifier. The data signal, however, is at 1550 nm in the transparent wavelength region where four-wave mixing sidebands are generated due to index modulations. The switch is used to sample a 160-Gb/s data signal with a temporal resolution of approximately 1.7 ps.
TL;DR: In this article, the nonlinear interaction of light in vacuum was studied in the context of four wave mixing, and a third-order nonlinear effective susceptibility of vacuum was introduced.
TL;DR: A review of the main directions of development, the most promising new techniques, and urgent applications of coherent four-photon methods of investigation of excited and ionized gas media is presented in this article.
Abstract: A review of the main directions of development, the most promising new techniques, and urgent applications of coherent four-photon methods of investigation of excited and ionized gas media is presented. It is demonstrated that the methods of coherent four-wave mixing (FWM) provide important spectrochronographic information on atoms and ions, allow selective studies of separate components of nonstationary gas and plasma systems with a complex composition using polarization-sensitive four-photon spectroscopy and coherent ellipsometry, and permit nonlinear-optical imaging of the spatial distribution of atoms and ions in excited gases and plasmas.
TL;DR: In this paper, a three-pulse four-wave mixing is used to control coherence and population transfer between ground and excited states using three-Pulse fourwave mixing, where the inherent vibrational dynamics of the system are utilized in timing the pulse sequence that controls the excitation process.
Abstract: Control of coherence and population transfer between the ground and excited states is reported using three-pulse four-wave mixing. The inherent vibrational dynamics of the system are utilized in timing the pulse sequence that controls the excitation process. A slight alteration in the pulse sequence timing causes a change in the observed signal from coherent vibration in the ground state to coherent vibration in the excited state. This control is demonstrated experimentally for molecular iodine. The theoretical basis for these experiments is discussed in terms of the density matrix for a multilevel system.
TL;DR: In this article, an experimental observation of modulation instability impairments on a two-channel WDM system at 2.5 Gb/s per channel repeaterless link comprising 100 km of dispersion shifted fiber is presented.
Abstract: We present an experimental observation of modulation instability (MI) impairments on a two-channel wavelength-division-multiplexed (WDM) system at 2.5 Gb/s per channel repeaterless link comprising 100 km of dispersion shifted fiber. When the channel spacing is close to the modulation instability frequency, channel depletion due to four-wave-mixing (FWM) interactions is resonantly enhanced and becomes the main source of system performance degradation. Numerical simulations agree well with the experiment and confirm that this effect dominates over the well known effect of MI amplification of noise. We discuss the influence of MI-induced resonant FWM as a function of channel spacing on WDM systems operating in the anomalous dispersion regime.
TL;DR: In this paper, the authors describe the coupling between experimentally observed optically heterodyne-detected (OHD) transient grating signals and the underlying molecular dynamics of heme proteins.
Abstract: Analytic relations are developed to describe the coupling between experimentally observed optically heterodyne-detected (OHD) transient grating (TG) signals and the underlying molecular dynamics of heme proteins. The heterodyne detection was implemented using a diffractive optical element to generate the phase-matched beam pattern along with a reference beam for OHD. The phase stability between the reference and signal fields using this approach is shown to be excellent over several hours of signal collection. Under small signal conditions this leads to an enhancement in signal-to-noise of several orders of magnitude. The grating excitation provides an inherent acoustic reference that can be used to determine the absolute signal phase. This enables separation of the real and imaginary components to the nonlinear susceptibility as well as determination of both the absorption anisotropy and its real counterpart, the phase anisotropy. The relationship between the phase anisotropy and the observed OHD TG sign...
Patent•
07 Jan 1999TL;DR: In this paper, four-wave mixing of transmitted signals in a lightwave transmission system is reduced by grouping the signals in pairs of adjacent frequencies, and increasing the frequency of every other pair by a fixed amount, where the fixed amount is less than the permitted variation of the ITU grid.
Abstract: Four-wave mixing of transmitted signals in a lightwave transmission system is reduced by 1) grouping the signals in pairs of adjacent frequencies, 2) increasing the frequency of every other pair by a fixed amount, where the fixed amount is less than the permitted variation of the ITU grid.
TL;DR: A nonlinear optical processor that is capable of true real-time conversion of spatial-domain images to ultrafast time-domain optical waveforms is presented and utilizes a cascaded second-order nonlinearity arrangement in a beta-barium borate crystal with type II phase matching.
Abstract: A nonlinear optical processor that is capable of true real-time conversion of spatial-domain images to ultrafast time-domain optical waveforms is presented. The method is based on four-wave mixing between the optical waves of spectrally decomposed ultrashort pulses and spatially Fourier-transformed quasi-monochromatic images. To achieve efficient wave mixing at a femtosecond rate we utilize a cascaded second-order nonlinearity arrangement in a ?-barium borate crystal with type??II phase matching. We use this ultrafast technique to experimentally generate several complex-amplitude temporal waveforms, with efficiency as high as 10%, by virtue of the cascaded nonlinearity arrangement.
TL;DR: In this article, the maximum allowed constant step size to be utilized in split-step Fourier method simulations, for obtaining a given accuracy in the FWM power evaluation, was analyzed, valid for any possible value of fiber dispersion, channel separation, channel power and number of channels considered in the simulation.
Abstract: Accurate evaluation of four-wave-mixing (FWM) contributions is one of the most time consuming problems in numerical simulations of wavelength-division-multiplexed light-wave systems. A too large constant step size can lead to widely overestimate the output FWM power. In this letter for the first time to our knowledge, I analyze the maximum allowed constant step size to be utilized in split-step Fourier method simulations, for obtaining a given accuracy in the FWM power evaluation. A very general rule is given, valid for any possible value of fiber dispersion, channel separation, channel power and number of channels considered in the simulation.
TL;DR: In this article, the effect of dispersion distributed fibers (DDFs) on the transmission characteristics of 4/spl times/10 Gb/s wavelength division multiplexing (WDM) systems was investigated experimentally and theoretically.
Abstract: The four-wave mixing (FWM) suppression effect of dispersion distributed fibers (DDF's), which have a nonuniform chromatic dispersion along their length, has been investigated experimentally and theoretically. We fabricated two different kinds of DDF by the vapor-phase axial deposition (VAD) method to clarify the FWM suppression effect. Moreover, we investigated experimentally the effect of our fabricated DDF's on the transmission characteristics of 4/spl times/10 Gb/s wavelength division multiplexing (WDM) systems. We confirmed that the proposed DDF's can not only suppress PWM but also improve the input power limitation for WDM systems.
TL;DR: In this paper, degenerate four-wave mixing studies of a set of new μ-oxo dimeric iron (III) phthalocyanine compounds excited by 532 nm picosecond pulses are reported.
TL;DR: In this paper, the propagation of strongly chirped pulses in an amplified fiber-optic communications system is experimentally investigated and the narrowing of the pulses is attributed to interplay between the initial chirp and the nonlinearity in the transmission line.
Abstract: The propagation of strongly chirped pulses in an amplified fiber-optic communications system is experimentally investigated. Spectral narrowing of the pulses is observed. The narrowing is attributed to interplay between the initial chirp and the nonlinearity in the transmission line. Four-wave mixing (FWM) between wavelength channels is found to be similar to that for unchirped nonreturn-to-zero (NRZ) pulses. Low error rate transmission over 720 km is achieved using these chirped pulses, which are generated by a transmitter based on a mode-locked fiber laser.
TL;DR: An analytical expression for the degenerate four-wave mixing signal produced in a medium composed of two-level atoms by pump and probe lasers of arbitrary intensities and parallel linear polarization, suffering negligible absorption and depletion, has been derived in this paper.
Abstract: An analytical expression for the degenerate four-wave mixing signal produced in a medium composed of two-level atoms by pump and probe lasers of arbitrary intensities and parallel linear polarization, suffering negligible absorption and depletion, has been derived. The Abrams–Lind approach [Opt. Lett.2, 94 and 3, 205 (1978)] for deriving the phase-matched polarization has been extended to find all the other higher-order polarization terms contributing to the signal. The signal field amplitude is expressed as an infinite series whose convergence rate depends on the intensity of the input fields and their detuning from resonance. The solution is successfully verified by comparison with a full numerical nonperturbative calculation and is found to be equivalent to the Abrams–Lind result in the limit of weak probe intensity. The result is used to calculate the saturation effects on spectral line shape that are relevant to simulation of molecular spectra obtained by degenerate four-wave mixing with saturating pump and probe fields. The result is extended to treat atomic motion in the case of forward geometry of the input beams.
21 Feb 1999
TL;DR: In this article, the relative impact of four-wave mixing (FWM) and cross phase modulation (XPM) on WDM transmission was investigated by treating them as noiselike impairments.
Abstract: The relative impact of four-wave mixing (FWM) and cross phase modulation (XPM) is investigated by treating them as noiselike impairments We show that XPM affects wavelength-division multiplexing (WDM) transmission more strongly than FWM for the range of fiber parameters investigated
TL;DR: In this paper, an experimental control and characterization of intramolecular dynamics are demonstrated with chirped femtosecond three-pulse four-wave mixing (FWM) signals on gas-phase I 2 and the degenerate laser pulses are resonant with the ground to B (excited) electronic transition.
Abstract: Experimental control and characterization of intramolecular dynamics are demonstrated with chirped femtosecond three-pulse four-wave mixing (FWM). The two-dimensional (spectrally dispersed and timeresolved) three-pulse FWM signal is shown to contain important information about the population and coherence of the electronic and vibrational states of the system. The experiments are carried out on gas-phase I 2 and the degenerate laser pulses are resonant with the X (ground) to B (excited) electronic transition. In the absence of laser chirp, control over population and coherence transfer is demonstrated by selecting specific pulse sequences. When chirped lasers are used to manipulate the optical phases of the pulses, the two-dimensional data demonstrate the transfer of coherence between the ground and excited states. Positive chirps are also shown to enhance the signal intensity, particularly for bluer wavelengths. A theoretical model based on the multilevel density matrix formalism in the perturbation limit is developed to simulate the data. The model takes into account two vibrational levels in the ground and the excited states, as well as different pulse sequences and laser chirp values. The analytical solution allows us to predict particular pulse sequences that control the final electronic state of the population. In a similar manner, the theory allows us to find critical chirp values that control the transfer of vibrational coherence between the two electronic states. Wave packet calculations are used to illustrate the process that leads to the observation of ground-state dynamics. All the calculations are found to be in excellent agreement with the experimental data. The ability to control population and coherence transfer in molecular systems is of great importance in the quest for controlling the outcome of laser-initiated chemical reactions.
TL;DR: In this paper, the effect of linear chirp on three-pulse four-wave mixing (FWM) experiments is explored and a theoretical formalism based on the density matrix formulation is presented and solved for a four-level system.
Abstract: Three-pulse four-wave mixing (FWM) is used here to study and control laser excitation processes. For general laser excitation processes, after a molecule interacts resonantly with a laser pulse, the molecule has a probability of being in the ground or in the excited state. Control over this process depends on the phase and amplitude of the electric fields that interact with the molecular system. Here we show how three-pulse FWM can be used to control the excitation of iodine molecules. Depending on the time delay between the first two pulses, the observed signal reflects the dynamics of the ground or excited state. A theoretical formalism based on the density matrix formulation is presented and solved for a four-level system. Experiments are found to be in excellent agreement with the theory. The influence of linear chirp on three-pulse FWM experiments is explored. Spectrally dispersed three-pulse FWM is found to be extremely useful for studying the effect of chirp on laser excitation of molecular systems. Experimental demonstrations of these effects are included.
TL;DR: In this article, the authors demonstrate an 80-mn wavelength shift with four-wave mixing (FWRW) using two orthogonally polarized pumps, and the power penalty at a 10/sup -9/ bit-error rate for a 2.5-Gb/s signal is less than 1.0 dB.
Abstract: Wavelength conversion using conventional single pump four-wave mixing in semiconductor optical amplifiers is limited to wavelength shifts of a few tens of nanometers due to the decrease of signal-to-noise ratio with wavelength shift. In this letter, we demonstrate an 80-mn wavelength shift with four-wave mixing (FWRW) using two orthogonally polarized pumps. The power penalty at a 10/sup -9/ bit-error rate for a 2.5-Gb/s signal is less than 1.0 dB. This result demonstrates the large wavelength shift capacity of this (FWM) technique.
TL;DR: In this paper, the authors presented a complete large-signal dynamic model of a wavelength converter or optical phase conjugator based on four-wave mixing in semiconductor optical amplifiers.
Abstract: We present a complete large-signal dynamic model of a wavelength converter or optical phase conjugator based on four-wave mixing in semiconductor optical amplifiers. The modified transfer matrix method (TMM) is used for implementing the large-signal dynamic model. It is possible for this model to involve not only forward traveling waves, but also backward traveling waves. Also, this model includes longitudinal variation of carrier-induced reflective index, /spl alpha/-parameter, gain, carrier density, photon density, reflection, and amplified spontaneous emission noise at each small section. Therefore, we can accurately evaluate frequency chirping, optical pulse pattern, and extinction ratio of the conjugate signal. Th eye-opening penalty has been calculated to investigate the effects of frequency chirping and extinction ratio on transmission performance.
ETSI1
TL;DR: In this article, the authors report theoretical and experimental results on the compensation of chromatic dispersion effects in microwave/millimeter-wave optical systems employing four-wave mixing induced in dispersion shifted fiber (DSF).
Abstract: The authors report theoretical and experimental results on the compensation of chromatic dispersion effects in microwave/millimeter-wave optical systems employing four-wave mixing (FWM) induced in dispersion shifted fiber (DSF). The technique is based on generating a phase-conjugated wave by means of FWM in a 12.7-km-long DSF placed at the midspan of the fiber-optic link. The experimental results show that by using FWM a complete compensation of the electrical carrier suppression effect in a 50-km standard single-mode-fiber optic link is achieved.