Showing papers on "Four-wave mixing published in 2000"
TL;DR: The development of the four wave mixing vibrational analog to 2D NMR is reported and its spectral selectivity, sensitivity to the interactions causing mode coupling, and ability to spectrally resolve isotopic mixtures are demonstrated.
Abstract: We report the development of the four wave mixing vibrational analog to 2D NMR and demonstrate its spectral selectivity, sensitivity to the interactions causing mode coupling, and ability to spectrally resolve isotopic mixtures. The method discriminates against uncoupled vibrational modes and isolates the features that are associated with intra- or intermolecular interactions.
142 citations
TL;DR: In this paper, a new scheme for all-optical signal reshaping is proposed and demonstrated, where strongly depleted mixing between a CW pump and a noisy non-return-to-zero (NRZ) signal in a common fiber can provide wavelength-converted signals exhibiting excellent intensity-noise cancellation.
Abstract: A new scheme for all-optical signal reshaping is proposed and demonstrated. The strongly depleted mixing between a CW pump and a noisy nonreturn-to-zero (NRZ) signal in a common fiber can provide wavelength-converted signals exhibiting excellent intensity-noise cancellation. Numerical simulations confirm almost complete suppression of intensity fluctuations, simultaneously occurring at several different wavelengths.
138 citations
TL;DR: In this article, the authors considered the detuning frequency dependence of χ(3), derived from the conversion efficiency, and showed that, within the range of detuning in the experiment, spectral-hole burning and carrier heating are responsible, and that their time constants, i.e., carrier relaxation time to the ground state and the phonon scattering time, are in the range 60 −140 and 200 −400 fs, respectively.
Abstract: Wavelength conversion using nondegenerate four-wave mixing in quantum-dot optical amplifiers is investigated. From the detuning frequency dependence of χ(3), derived from the conversion efficiency, we consider that, within the range of detuning in the experiment, spectral-hole burning and carrier heating are responsible, and that their time constants, i.e., carrier relaxation time to the ground state and the phonon scattering time, are in the range of 60–140 and 200–400 fs, respectively. This indicates that the carrier supply to the ground level via relaxation from the higher levels is very fast and that a broad conversion bandwidth comparable to that of quantum-well devices is ensured.
109 citations
TL;DR: In this article, the femtosecond time-resolved four-wave-mixing (FWM) spectroscopy was used to investigate wave packet dynamics on different potential energy surfaces.
Abstract: This paper reviews results on wave packet dynamics investigated by means of femtosecond time-resolved four-wave-mixing (FWM) spectroscopy. First, it is shown that by making use of the various degrees of freedom which are offered by this technique information about molecular dynamics on different potential-energy surfaces can be accessed and separated from each other. By varying the timing, polarization, and wavelengths of the laser pulses as well as the wavelength of the detection window for the FWM signal, different dynamics are coherently excited and probed by the nonlinear spectroscopy. As a model system we use iodine in the gas phase. These techniques are then applied to more-complex molecules (gas phase: benzene, toluene, a binary mixture of benzene and toluene; solid state: polymers of diacetylene matrix-isolated in single crystals of monomer molecules). Here, ground-state dynamics are investigated first without any involvement of electronically excited states and then in electronic resonance to an absorption transition in the investigated molecules. Signal modulations result which are due to wave packet motion as well as polarization beats between modes in different molecules. Phase and intensity changes yield information about intramolecular vibrational energy redistribution, population decay (T1), phase relaxation (T2), and coherence times.
88 citations
TL;DR: In this article, the advantages of using a short length of fiber to generate broadband four-wave mixing are proposed and verified using wavelength conversion experiments for different lengths of a previously developed high-nonlinearity fibre with a nonlinear coefficient of 13.8 W-1km-1.
Abstract: Several advantages of using a short length of fibre to generate broadband four-wave mixing are proposed and verified using wavelength conversion experiments for different lengths of a previously developed high-nonlinearity fibre with a nonlinear coefficient of 13.8 W-1km-1. Consequently, 91.3 nm broadband simultaneous wavelength conversion is demonstrated using a 100 m long section of the developed fibre.
77 citations
TL;DR: Broad-bandwidth light pulses with different frequencies, extending from the IR to the UV, are simultaneously generated when two noncollinear, ultrafast laser pulses from a visible dual-frequency laser propagate through bulk isotropic transparent media such as common glass.
Abstract: Broad-bandwidth light pulses with different frequencies, extending from the IR to the UV, are simultaneously generated when two noncollinear, ultrafast laser pulses from a visible dual-frequency laser propagate through bulk isotropic transparent media such as common glass. This phenomenon, which is believed to have been previously unreported, can be explained by a cascade of highly nondegenerate four-wave-mixing processes and corresponds to a coherent scattering effect with geometrically minimized phase mismatch. Frequency-upconverted beams were observed up to the 11th order.
75 citations
TL;DR: In this article, the nonlinear propagation equation taking into account gain spectrum dynamic gain saturation which depends on carrier depression, carrier heating, and spectral hole-burning, group velocity dispersion, self-phase modulation, and two-photon absorption was analyzed.
Abstract: We have numerically analyzed nondegenerate four-wave mixing (FWM) among short optical pulses in a semiconductor optical amplifier (SOA) by the finite-difference beam propagation method (FD-BPM). We used the nonlinear propagation equation taking into account gain spectrum dynamic gain saturation which depends on carrier depression, carrier heating, and spectral hole-burning, group velocity dispersion, self-phase modulation, and two-photon absorption. To analyze FWM in an SOA, the evolution in time and spectral domain of two input optical pulses with different frequencies during propagation was calculated. From this simulation, it has become clear that the method me used here is a very useful technique for simulating FWM characteristics in SOA's. We also found that the wavelength dependence of the gain is crucial if the detuning is larger than 1 THz.
73 citations
TL;DR: In this paper, Deng et al. developed a three-dimensional quantum- mechanical description, based on the slowly-varying-envelope approximation, for four-wave mixing in Bose-Einstein condensates using the time-dependent Gross-Pitaevskii equation.
Abstract: A recent experiment [Deng et al., Nature (London) 398, 218 (1999)] demonstrated four-wave mixing of matter wave packets created from a Bose-Einstein condensate. The experiment utilized light pulses to create two high-momentum wave packets via Bragg diffraction from a stationary Bose-Einstein condensate. The high-momentum components and the initial low-momentum condensate interact to form a new momentum component due to the nonlinear self-interaction of the bosonic atoms. We develop a three-dimensional quantum- mechanical description, based on the slowly-varying-envelope approximation, for four-wave mixing in Bose-Einstein condensates using the time-dependent Gross-Pitaevskii equation. We apply this formulation to describe the experimental observations and to make predictions. We examine the role of phase-modulation, momentum, and energy conservation (i.e., phase matching), and particle number conservation in four-wave mixing of matter waves, and develop simple models for understanding our numerical results.
69 citations
TL;DR: In this article, the total polarization induced in the molecular sample by the interaction with several femtosecond laser pulses is determined by solving the time-dependent Schrodinger equation for the nuclear dynamics in coupled electronic states numerically exact.
Abstract: We extend a method proposed by Seidner et al. [J. Chem. Phys. 103, 3998 (1995)] to extract directional terms from a time-dependent molecular polarization to obtain time-resolved four-wave-mixing (FWM) signals. Instead of employing perturbation theory, the total polarization induced in the molecular sample by the interaction with several femtosecond laser pulses is determined by solving the time-dependent Schrodinger equation for the nuclear dynamics in coupled electronic states numerically exact. Repeating the calculation for several combinations of relative phases of the involved fields leads to a linear system of equations for the contributions emitted in different directions. Gas-phase I2 molecules serve as a numerical example.
58 citations
TL;DR: In this paper, the imaging properties of nonlinear coherent four-wave mixing optical microscopes are analyzed under conditions of high numerical aperture with a model that circumvents the need to use the slowly varying envelope approximation.
Abstract: An analysis of the imaging properties of nonlinear coherent four-wave mixing optical microscopes is presented. The generation and propagation of coherent signals are considered under conditions of high numerical aperture with a model that circumvents the need to use the slowly varying envelope approximation. Calculations of coherent anti-Stokes Raman scattering signals show that diffraction effects play a prominent role in the spatial distribution of the coherent signal intensity. It is emphasized that, unlike for fluorescence microscopy, the detected signal is not a straightforward convolution of a point-spread function and the object but is shaped by the complex interplay of object size and coherent buildup dynamics.
57 citations
TL;DR: Diffractive optics are applied to six-wave mixing processes to provide a single optic approach to attaining the required, relatively complex, phase-matching geometry to discriminate against lower-order nonlinear responses.
Abstract: Diffractive optics are applied to six-wave mixing processes to provide a single optic approach to attaining the required, relatively complex, phase-matching geometry to discriminate against lower-order nonlinear responses. The diffractive optics were designed specifically for broad-bandwidth operation and passive phase locking of the appropriate pulse pairs for use in femtosecond two-dimensional Raman studies of the dynamic structure of liquids. The fifth-order signal was studied in liquid CS2; two different colors were used for the excitation and the probe to reduce background scatter, as were two different phase-matching geometries with different degrees of suppression of cascaded third-order processes.
TL;DR: In this article, the roles of pulse sequence and pulse chirp were explored using femtosecond three-pulse four-wave mixing (FWM) experiments on gas phase I2 and the degenerate laser pulses are resonant with the transition between the X (6gY ) ground and B (0uY ) excited electronic states.
Abstract: The roles of pulse sequence and pulse chirp were explored using femtosecond three-pulse four-wave mixing (FWM). The experiments were carried out on gas-phase I2 and the degenerate laser pulses are resonant with the transition between the X (6gY ) ground and B (0uY ) excited electronic states. Impulsive excitation leads to the observation of vibrational coherence in the ground and the excited states. Control over the observed population and vibrational coherence is achieved by using specific pulse sequences. Using chirped pulses results in changes in vibrational coherence. When the FWM signal is spectrally dispersed, the two-dimensional data (wavelength and time delay) provide important spectroscopic information about the intramolecular dynamics of both electronic states. This information is not typically available in time or spectrally integrated measurements. A theoretical foundation for these observations based on the density matrix formalism is briefly discussed. Copyright 2000 John Wiley & Sons, Ltd.
Patent•
08 Dec 2000
TL;DR: In this article, the dispersion shifted medium is designed to produce a set of discrete wavelengths, by such means as four wave mixing, whose frequencies are related to the wavelength of the pulsed laser sources and the repetition frequency of the resonant cavity.
Abstract: This invention provides a means for generating multiple wavelengths in an integrated manner using a resonant cavity containing dispersion shifted medium and coupled to at least one pulsed laser source. The laser sources emit radiation at a particular wavelength and are pulsed in a manner synchronously related to the round trip time of the resonant cavity. The dispersion shifted medium is designed to produce a set of discrete wavelengths, by such means as four wave mixing, whose frequencies are related to the wavelength of the pulsed laser sources and the repetition frequency of the resonant cavity. The reflective elements of the resonant cavity are designed to contain the radiation of the laser sources within the resonant cavity and to transmit an equal amount of each of the generated set of wavelengths.
TL;DR: In this article, a time-resolved four-wave mixing in an InAs/InGaAs/GaAs electrically pumped quantum-dot amplifier is measured at room temperature for different applied bias currents going from optical absorption to gain of the device.
Abstract: Time-resolved four-wave mixing in an InAs/InGaAs/GaAs electrically pumped quantum-dot amplifier is measured at room temperature for different applied bias currents going from optical absorption to gain of the device. The four-wave mixing signal from 140 fs pulses shows a transition from a delayed photon-echo response in the absorption regime to a prompt free polarization decay in the gain regime. This corresponds to a pronounced reduction of the dephasing time from 250 fs at zero bias to less than 50 fs at the maximum applied current. The four-wave mixing response at transparency of the device shows a composite structure with both photon echo and free-polarization decay. This is a signature of the digital occupation number in quantum dots, resulting at transparency in a signal from dots occupied with either zero or two excitons corresponding to absorption or gain of the dot ground state.
TL;DR: In this paper, a set of nonlinear coupled equations describing four-wave mixing with matter waves was derived and solved analytically without utilizing the undepleted pump approximation, and the results were shown to be consistent with the Gross-Pitaevskii nonlinear Schrodinger equation.
Abstract: Starting from the Gross-Pitaevskii nonlinear Schrodinger equation, we derive a set of nonlinear coupled equations describing four-wave mixing with matter waves and solve them analytically without utilizing the undepleted pump approximation.
TL;DR: In this paper, the authors developed two algorithms, using frequency difference triangles and frequency difference squares, that can determine the total number of FWM signals falling onto the operating band and each channel, respectively, of unequal-spaced WDM systems.
Abstract: Recently, unequal-spaced channel-allocation techniques have been studied and analyzed to reduce four-wave-mixing (FWM) crosstalk in high-capacity, long-haul wavelength-division multiplexing (WDM) transmission systems. It will be helpful to system designers if there exists a fast tool to measure the strength of FWM crosstalk in such WDM systems. In this paper, we develop two algorithms, using frequency difference triangles and frequency difference squares, that can determine the total numbers of FWM signals falling onto the operating band and each channel, respectively, of unequal-spaced WDM systems. By knowing these two numbers, one can adjust the system parameters, such as minimum channel spacing, in order to keep a good balance on the adverse effects of FWM crosstalk and interchannel interference, or avoid the assignment of channels at locations with the most severe crosstalk.
TL;DR: In this paper, the authors provide a fundamental understanding of time-resolved four-wave mixing (FWM) processes based on a large body of experimental measurements on a model system consisting of isolated iodine molecules.
Abstract: This article seeks to provide a fundamental understanding of time-resolved four-wave mixing (FWM) processes based on a large body of experimental measurements on a model system consisting of isolated iodine molecules. The theoretical understanding is based primarily on a diagrammatic approach. Doublesided Feynman diagrams are used to classify and describe the coherent FWM processes involved in the signal obtained with each pulse sequence. Different pulse sequences of degenerate femtosecond pulses are shown to control the optical phenomena observed, that is transient grating, reverse-transient grating, photon echo and virtual photon echo. The experimental data reveal clear differences between the nonlinear optical phenomena. We find that the virtual photon echo sequence k1 - k2 + k3 is the most efficient for controlling the observation of ground - or excited-state dynamics. The strategy followed to make this assessment was to compare transients when the time delay between two of the three pulses set in or ...
TL;DR: In this article, a nearly transform-limited nanosecond laser source at 120 nm is constructed with difference-frequency mixing, which is used to perform the first Doppler-free VUV measurement.
Abstract: We describe techniques for laser spectroscopy in the vacuum-UV (VUV) spectral region that combine high spectral resolution with high absolute accuracy. A nearly transform-limited nanosecond laser source at 120 nm is constructed with difference-frequency mixing. This source is used to perform the first, to our knowledge, Doppler-free VUV measurement. We measure the inherently narrow 11S–21S two-photon transition in atomic helium with a spectral resolution of 7 parts in 108 (180 MHz), the narrowest line width so far observed at such short wavelengths. Careful measurements of optical phase perturbations allow us to determine the absolute frequency of the line center to a fractional uncertainty of 1 part in 108. Improvements now in progress should reduce this uncertainty to 2 parts in 109.
TL;DR: It is demonstrated that the transient coherent nonlinearity (coherent artifact) affecting the pump-probe response of semiconductor optical amplifiers can be experimentally separated from the incoherent transient.
Abstract: We demonstrate that the transient coherent nonlinearity (coherent artifact) affecting the pump-probe response of semiconductor optical amplifiers an be experimentally separated from the incoherent transient. The technique is based on measuring the mirror component of the coherent artifact which is a background-free four wave mixing signal at a different frequency with respect to the transmitted probe in a heterodyne detection scheme. Measurements on amplifiers of different length reveal strong deviations from the commonly expected symmetric shape of the coherent artifact in case of long waveguides.
TL;DR: In this paper, the optical sampling four-wave mixing technique is used to reveal the exciton dynamical processes in GaAs quantum wells at low temperatures, which can therefore be observed rapidly in the common measurement system.
TL;DR: In this article, a polarisation-insensitive wavelength converter using four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) was realized, which uses a novel polarisation diversity scheme which requires only one SOA.
Abstract: A polarisation-insensitive wavelength converter using four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) has been realised. The converter uses a novel polarisation-diversity scheme which requires only one SOA. Polarisation-insensitive wavelength conversion (< 1 dB polarisation sensitivity) and a near constant (< 3 dB variation) conversion efficiency was achieved over a range of 26 nm.
TL;DR: Higher-order four-wave mixing effects are evaluated in WDM systems and results show that higher-order FWM crosstalk could be significant in unequal channel-spacing W DM systems where the first- order FWM is not a problem.
Abstract: Higher-order four-wave mixing effects are evaluated in WDM systems. Calculated and measured results show that higher-order FWM crosstalk, though small compared to the first-order FWM crosstalk, could be significant in unequal channel-spacing WDM systems where the first-order FWM is not a problem.
TL;DR: In this paper, the authors investigated the optical crosstalk caused by nonlinear interactions in short and long-haul wavelength division multiplexion transmission systems called inter-domain interfaces.
Abstract: This paper reports on an investigation of optical crosstalk caused by nonlinear interactions in short- and long-haul wavelength division multiplexion transmission systems called inter-domain interfaces. These investigations are based on numerical simulations of multichannel optical transmission systems, using specialist software: Gigabit Optical Line Designer v.2.0 from Virtual Photonics. The nonlinear phenomena in fibres that have to be taken into account include four-wave mixing, self-phase modulation, cross-phase modulation, stimulated Raman scattering, stimulated Brillouin scattering and nonlinear interactions in erbium-doped fibre amplifiers.
TL;DR: The theory for temporally multidimensional, electronically resonant four-wave-mixing (FWM) spectroscopy based on broadband light interferometry is developed in this article.
Abstract: The theory for temporally multidimensional, electronically resonant four-wave-mixing (FWM) spectroscopy based on broadband light interferometry is developed. Both homodyne and heterodyne detection are considered. Upon spectrally resolving the signal, the electronic Bohr frequency is seen to be extremely down-converted, even to zero frequency, but only with homodyne detection. These very low frequency fringes, referred to as radiation difference oscillations, are well known in the interferometric coherent Raman broadband light spectroscopies. Such low frequency fringes permit interferometry in the optical region using Nyquist criteria corresponding to far infrared sampling rates. Possible applications are illustrated by simulations of the two-dimensional third order signals from an electronic two-level system in a variety of ``baths.'' It is seen how homogeneous and inhomogeneous line-shaping mechanisms manifest themselves differently and revealingly in the free induction decay, the photon echo decay and their cross term components of the FWM signal.
TL;DR: In this article, the polarization of the VUV light generated by four-wave sum-frequency mixing process ω4=2ω1+ω2 in mercury vapor at room temperature is analyzed in detail.
Abstract: The polarization of the VUV light generated by four-wave sum-frequency mixing process ω4=2ω1+ω2 in mercury vapor at room temperature is analyzed in detail. Due to the specific two-photon transition used to enhance the nonlinear process, the polarization of the VUV wave is shown to be identical to the polarization of the wave at the frequency ω2. In particular, circularly polarized VUV is observed with degree of circular polarization exceeding 0.99.
TL;DR: In this paper, the generation of four-wave mixing (FWM) products inside a +30 dBm output power booster Er/sup 3-//Yb/Sup 3+/ amplifier is reported.
Abstract: The generation of four-wave mixing (FWM) products inside a +30 dBm output power booster Er/sup 3-//Yb/sup 3+/ amplifier is reported. The corresponding nonlinear Kerr parameter /spl gamma/ was derived by measurement of the FWM efficiency between two co-propagating signal pumps. Experimental and theoretical FWM transmission impairments have been confirmed for a 2.5 Gbit/s eight-channel WDM transmission system.
TL;DR: In this paper, the effect of the intramolecular coupling on the resonances associated to the four-wave mixing signal is studied in the context of a local homogeneous-linewidth third-order perturbation model.
TL;DR: In this paper, a real-time spatial-temporal processor based on cascaded nonlinearities converts space-domain images to time-domain waveforms by the interaction of spectrally decomposed ultrashort pulses and spatially Fourier-transformed images carried by quasi-monochromatic light waves.
Abstract: A real-time spatial–temporal processor based on cascaded nonlinearities converts space-domain images to time-domain waveforms by the interaction of spectrally decomposed ultrashort pulses and spatially Fourier-transformed images carried by quasi-monochromatic light waves. We use four-wave mixing, achieved by cascaded second-order nonlinearities with type II noncollinear phase matching, for femtosecond-rate processing. We present a detailed analysis of the nonlinear mixing process with waves containing wide temporal and angular bandwidths. The wide bandwidths give rise to phase-mismatch terms in each process of the cascade. We define a complex spatial–temporal filter to characterize the effects of the phase-mismatch terms, modeling the deviations from the ideal system response. New experimental results that support our findings are presented.