Showing papers on "Four-wave mixing published in 1985"
TL;DR: In this paper, a balanced homodyne detector was used to measure the optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms.
Abstract: Squeezed states of the electromagnetic field have been generated by nondegenerate four-wave mixing due to Na atoms in an optical cavity. The optical noise in the cavity, comprised of primarily vacuum fluctuations and a small component of spontaneous emission from the pumped Na atoms, is amplified in one quadrature of the optical field and deamplified in the other quadrature. These quadrature components are measured with a balanced homodyne detector. The total noise level in the deamplified quadrature drops below the vacuum noise level.
1,315 citations
TL;DR: In this article, a comprehensive discussion of optical transitions in these microstructures is given, including excitonic effects and the specific features of room-temperature exciton resonances.
Abstract: We review the nonlinear-optical effects observed at room temperature in semiconductor quantum-well structures photoexcited near the band gap. A comprehensive discussion of optical transitions in these microstructures is given, including excitonic effects and the specific features of room-temperature exciton resonances. Experimental investigations using continuous-wave, picosecond-, and femtosecond-laser sources are presented. They show extremely efficient nonlinear processes. In the case of excitations that are long compared with the exciton-ionization time, the induced changes in absorption and refraction do not depend on the wavelength or on the duration of excitation. These changes depend only on the density of absorbed photons and are interpreted in terms of electron–hole plasma screening and band filling. In contrast, for ultrashort excitation, nonlinear processes depend critically on the excitation wavelength. The selective generation of excitons is found to produce effects larger than a plasma of the same density. This unexpected result is shown to arise from the low temperature of the exciton gas before it interacts with the lattice and from the decrease of screening that is the reduced dimensionality of quantum-well structures.
321 citations
TL;DR: Methods of suppressing undesired effects such as stimulated Brillouin scattering are presented as is a technique for providing the phase-shifted local oscillator wave necessary for the detection of squeezing.
Abstract: Nondegenerate four-wave mixing in a single-mode optical fiber is proposed as a method of squeezed state generation. An analysis of the near-degenerate mixing process for forward propagation in realistic fibers is presented along with the theory of an experimentally feasible detection strategy. The effects of the quantum nature of the optical nonlinearity and absorption are modeled by treating the fiber medium as a collection of anharmonic oscillators. Methods of suppressing undesired effects such as stimulated Brillouin scattering are presented as is a technique for providing the phase-shifted local oscillator wave necessary for the detection of squeezing. Preliminary experiments on fiber characterization and the detection of four-wave parametric fluorescence are described.
137 citations
TL;DR: In this article, the authors studied the mechanism and the dynamics of degenerate four-wave mixing in a nematic liquid crystal film, where nanosecond laser pulses are used to generate an index grating associated with the changes in the density and in the order parameter.
Abstract: We have studied the mechanism and the dynamics of degenerate four-wave mixing in a nematic liquid crystal film. Nanosecond laser pulses are used to generate an index grating associated with the changes in the density and in the order parameter. We have measured and analyzed the contributions from these two mechanisms, their interference effects rise and decay time constants, and have also performed a detailed analysis of the diffraction efficiency. This study quantitatively characterizes the potential usefulness of nematie films for four-wave mixing based applications.
95 citations
IBM1
TL;DR: In this article, the authors show that in order to describe completely the coherent coupling between the pump and probe pulses in a pump-probe measurement of transient absorption, the influence of induced phase gratings must be included.
Abstract: We show that in order to describe completely the coherent coupling between the pump and probe pulses in a pump– probe measurement of transient absorption, the influence of induced phase gratings must be included. The importance of phase gratings is demonstrated experimentally for the case of a bleachable dye and analyzed in terms of transient four-wave mixing. These results are relevant to the interpretation of pump–probe measurements on all time scales performed with pulses from a single laser, particularly when the pulse duration is comparable with the material response time.
90 citations
TL;DR: Degenerate nonlinear light scattering in LiTaO(3) caused by parametric forward four-wave mixing of waves with orthogonal polarization is reported.
Abstract: Degenerate nonlinear light scattering in LiTaO3 caused by parametric forward four-wave mixing of waves with orthogonal polarization is reported. Scattered light is located on a cone whose apex angle is defined by the phase-matching condition. The photorefractive-type nonlinearity involved in this process is caused by the excitation of spatially oscillating photovoltaic currents directed normal to the optical axis and the subsequent formation of a volume space-charge field modulating the refractive index.
77 citations
IBM1
TL;DR: Nondegenerate four-wave mixing in an optical fiber is shown to attenuate one quadrature of random sideband fluctuations created by external modulators, fitting a theory of the nonlinear interaction that includes nonlinear dispersion.
Abstract: Nondegenerate four-wave mixing in an optical fiber is shown to attenuate one quadrature of random sideband fluctuations created by external modulators. A theory of the nonlinear interaction that includes nonlinear dispersion fits the results. Analogous experiments on quantum noise inputs should prove successful.
77 citations
TL;DR: It is shown that the 1-Hz frequency shift previously observed in the output of a self-pumped phase conjugator that used photorefractive BaTi${\mathrm{O}}_{3}$ is the result of this inherent property of four-wave mixing.
Abstract: We present theory and experiments to show that the efficiency of four-wave mixing in photorefractive materials can be enhanced by use of optical waves of slightly different frequencies The optimum frequency shift scales inversely with the response time of the material We show that the \ensuremath{\sim}1-Hz frequency shift previously observed in the output of a self-pumped phase conjugator that used photorefractive BaTi${\mathrm{O}}_{3}$ is the result of this inherent property of four-wave mixing
69 citations
TL;DR: In this paper, the phase conjugation is performed in a fluorescein film by a cw Ar ion laser of the wavelength 0.488 μm in a degenerate four-wave mixing (DFWM) configuration.
66 citations
TL;DR: The four-wave mixing process can suppress amplified spontaneous emission by preventing the excitation of the $3d$ level due to an interference between two different pathways connecting the ground ($3s$) and $3p$ states.
Abstract: Two-photon-resonant excitation of the sodium $3d$ level can lead to the generation of new frequencies either by amplified spontaneous emission at the $3d\ensuremath{\rightarrow}3p$ transition frequency or by a resonantly enhanced four-wave mixing process. Competition between these two processes has been observed. The four-wave mixing process can suppress amplified spontaneous emission by preventing the excitation of the $3d$ level due to an interference between two different pathways connecting the ground ($3s$) and $3d$ states.
63 citations
TL;DR: In this article, a low-intensity probe beam of frequency ω−δω inside a (GaAl)As semiconductor laser operating above threshold at the pump frequency was demonstrated.
Abstract: Intracavity nearly degenerate four‐wave mixing has been demonstrated by injecting a low intensity probe beam of frequency ω−δω inside a (GaAl)As semiconductor laser operating above threshold at the pump frequency ω. Conjugated reflectivities as high as 5000 together with a 25% energy conversion efficiency are reported with only a few milliwatt pump power. Additional peaks related to the ac stark effect have been observed at a detuning which depended on the pump power. This process could be useful for the study of instabilities occurring in lasers as well as for optical amplification in laser diodes.
TL;DR: The measured onset or threshold of oscillation as a function of photorefractive gain and intensity agrees with theory.
Abstract: Photorefractive resonators exhibit an extremely small frequency difference (Deltaomega/omega~10(-15)) between the oscillating and pumping beams. The observed frequency difference is proportional to cavity-length detuning. This dependence is explained by a photorefractive phase shift that is due to slightly nondegenerate two-wave mixing that compensates for cavity detuning and satisfies the round-trip phase condition for steady-state oscillation. The measured onset or threshold of oscillation as a function of photorefractive gain and intensity agrees with theory.
TL;DR: In this paper, a large-scale 1.9-psec modulation associated with the fine structure of the 3S-3P state is observed at low buffer-gas pressures and low Na-vapor temperatures.
Abstract: Time-delayed four-wave mixing (TDFWM) on the 3S-3P transition in Na vapor has been studied using intense 7-nsec pulses from a broadband laser. Large-scale 1.9-psec modulation associated with the fine structure of the 3P state is observed throughout. At low buffer-gas pressures and low Na-vapor temperatures, pulse-induced relaxation effects are observed while at higher Na-vapor temperatures an anomalous response develops. In the normal region the TDFWM signal is interpreted in terms of either accumulated free decays or photon echoes. We estimate the relaxation induced by the excitation pulses.
TL;DR: A simple model has been developed to estimate the corresponding parallel-processing capabilities of semi-conductor-based, all-optical, parallel- processing digital computing systems.
Abstract: Studies of the angular dependence of cw degenerate four-wave mixing in n-type InSb have yielded a value for the diffusion length, l(D), of 60 +/- 2 microm. From this, the dependence of l(D) on photoexcited carrier concentration is calculated. A simple model has been developed to estimate the corresponding parallel-processing capabilities of semi-conductor-based, all-optical, parallel-processing digital computing systems.
TL;DR: In certain conditions, the diffraction efficiency is shown to be exactly proportional to the inverse of the object beam intensity, and the dependence of the range of beam ratios over which inversion occurs on the experimental parameters of total writing beam intensity and applied electric field is investigated.
Abstract: In this paper, we consider a two-wave mixing system using a photorefractive medium and compute the diffraction efficiency as a function of the writing beam ratios. In certain conditions, the diffraction efficiency is shown to be exactly proportional to the inverse of the object beam intensity. Experimental results, obtained using a Bi12GeO20 crystal, are compared to the theoretical expression. In particular, we investigate the dependence of the range of beam ratios over which inversion occurs on the experimental parameters of total writing beam intensity and applied electric field. Results of performing inversion of gray-scale objects using a degenerate four-wave mixing setup are shown.
TL;DR: In this paper, a family of nonlinear four-wave mixing techniques that are capable of site-selective organic spectroscopy is presented, and three lasers are used in the methods in order to achieve fully resonant mixing.
Abstract: A family of nonlinear four-wave mixing techniques that are capable of site-selective organic spectroscopy are presented. Three lasers are used in the methods in order to achieve fully resonant mixing. Three lasers are shown to provide better sensitivity, selectivity, and versatility in the study of ground and excited electronic state vibrational spectroscopy. New approaches become possible in the establishment of resonances that translate the output signal from the normal Stokes or anti-Stokes side of the lasers to intermediate positions that are free of fluorescence interference. These new methods are divided into Multiply Enhanced Parametric Spectroscopy (MEPS) and Multiply Enhanced Nonparametric Spectroscopy (MENS), depending upon the spectroscopic characteristics for site-selective applications. The characteristics of MEPS and MENS are found to be quite different and depend upon the number and separation of the sites, the power of the lasers, the relative shifts of the levels, and the correlation effects in the inhomogeneous broadening. The feasibility of MENS and the site-selective capability of both CARS and MENS is demonstrated experimentally with the use of the pentacene: p-terphenyl system as a model.
TL;DR: In this article, an analytic solution for the intensity distribution of two counterpropagating pump waves within a saturable absorber is derived from this distribution, the spatial variation of the nonlinear absorption and coupling constants that appear in the coupled-amplitude equations for the probe and the signal (i.e., conjugate) waves are determined.
Abstract: An analytic solution for the intensity distribution of two counterpropagating pump waves within a saturable absorber is derived. From this distribution, the spatial variation of the nonlinear absorption and coupling constants that appear in the coupled-amplitude equations for the probe and the signal (i.e., conjugate) waves are determined. These coupled-amplitude equations are solved numerically in a noniterative manner, leading to a prediction for the phase-conjugate reflectivity. The results of the exact theory are compared with those of previously published theories. It is found that at large values of the input-pump intensities, the predicted phase-conjugate reflectivity is larger when pump-absorption effects are included in the theory.
TL;DR: In this paper, a two-photon resonantly enhanced four-wave mixing process in krypton was used to generate coherent, narrow-band, tunable radiation in the extreme-ultraviolet spectral region.
Abstract: Coherent, narrow-band, tunable radiation in the extreme-ultraviolet spectral region was generated by a two-photon resonantly enhanced four-wave mixing process in krypton. Sum-generated radiation was produced near 942, 928, and 923 A with power efficiencies as high as 10−5. Difference-generated radiation near 1312 A was also detected.
TL;DR: In this article, the authors studied the efficiency of laser-induced gratings as a function of the photon energies and the intensities of the two interfering beams as well as the temporal evolution of transmitted and diffracted beams.
Abstract: There are numerous optical nonlinearities that may lead to the creation of laser-induced gratings and to four-wave mixing in the vicinity of the band edge. In direct, large-gap semiconductors some of the most dominant processes are a density-dependent (collision) broadening of the excitonic resonances, two-polariton transitions to the excitonic molecule, and the formation of an electron–hole plasma. The appearance of the diffracted beams is described both in the wave and in the quasi-particle picture. The relation is sketched between four-wave mixing and other scattering experiments, such as two-photon Raman scattering. The efficiency of the laser-induced gratings is studied as a function of the photon energies and the intensities of the two interfering beams as well as the temporal evolution of transmitted and diffracted beams.
TL;DR: In this article, three tunable lasers are used to generate a fully resonant nonparametric process that generates new coherent output at a higher energy than fluorescence interference in condensed phase molecular systems.
Abstract: Three tunable lasers are used to generate a fully resonant nonparametric process that generates new coherent output at a higher energy than fluorescence interference in condensed phase molecular systems. The pentacene:p‐terphenyl system is used as a model to test the basic ideas of the method and to compare the results with comparable spectra obtained with a parametric process. The resonance enhancement is shown to reflect intermode coupling between different vibrational and vibronic modes. Interference is observed between transitions of different pentacene sites that reflects the differences in the parametric and nonparametric processes. These differences become the dominant characteristic determining the potential for four‐wave nonlinear mixing methods to provide resolution within inhomogeneously broadened electronic bands.
TL;DR: In this paper, a flashlamp-pumped dye laser synchronized on a cw dye laser was used to investigate degreenerate four-wave mixing in sodium vapor.
Abstract: Degenerate four-wave mixing in sodium vapor is investigated using a flashlamp-pumped dye laser synchronized on a cw dye laser. At low atomic density, the reflectivity versus the pump intensity and the line shapes are in good agreement with theoretical predictions in the case of both plane waves and Gaussian beams. At high atomic density, reflectivities much higher than unity have been observed. The influence of the pump imbalance has been studied as well as the deformation of the wave front of the conjugated beam introduced by the pump beams. In the high-atomic-density case, the theoretical problem is more complex, and our experimental results exhibit only qualitative agreement with theory.
TL;DR: In this paper, an exact solution to the stationary holographic degenerate four-wave mixing in both transmission and reflection geometry for photorefractive media is obtained, and the effects of pump depletion and light absorption in the non-linear dynamic medium are rigorously taken into account.
TL;DR: In this paper, the authors reported the first evidence of a near-resonant four-wave parametric interaction in gaseous ammonia using a single-pass NH 3 cell pumped by a 9R16 CO 2 TEA laser.
TL;DR: Observation de resonances de Hanle pour un melange coherent de 4 ondes a l'etat fondamental de Na: leur intensite augmente et leur largeur diminue quand augmente the pression du gaz tampon.
Abstract: Hanle resonances for coherent four-wave mixing in the ground state of Na are reported whose intensity increases and whose linewidth decreases with increasing inert buffer gas pressure. In 10-mTorr Na vapor with 4 atm of argon, resonances of less than 35 mG full width at half maximum are observed. The high resolution permits direct observation of the fundamental homogeneous broadening mechanisms for the Zeeman coherences responsible for four-wave mixing.
TL;DR: In this paper, a synchronous scanning method for fully resonant four-wave mixing experiments with three input frequencies was developed for the vibrational and vibronic resonances that are coupled, consequently simplifying the spectral information obtained.
Abstract: New synchronous scanning methods are developed for fully resonant four-wave mixing experiments with three input frequencies. Enhanced sensitivity and selectivity are observed for the vibrational and vibronic resonances that are coupled, consequently simplifying the spectral information obtained. The factors affecting selectivity and spectral simplification are discussed. Spectra obtained with the use of two-laser and three-laser CARS reveal various schemes of multiple resonance. Under resonant excitation at moderate power, saturation and power broadening reduce the effective electronic resonance enhancement. Resonances based on coupling between vibrational and vibronic levels are less susceptible to such power-induced phenomena. It is demonstrated that four-wave mixing with three input lasers provides the capabilities of measuring intermode vibronic coupling terms of the third-order susceptibility and performing fully resonant nonparametric four-wave mixing experiments that have the same characteristics as CSRS but are free from molecular fluorescence.
TL;DR: In this paper, the use of a fourth input beam in photorefractive four wave mixing systems is investigated, which affects the local modulation index of the photoinduced grating structures thus allowing real-time modification of the output from such systems.
TL;DR: A three-laser technique for performing fully resonant, non-parametric four-wave mixing is demonstrated in pentacene-doped benzoic acid at 2 K.
TL;DR: In this article, the authors reported the first λ∼1.5 μm picosecond near-bandgap nonlinear absorption and degenerate four-wave mixing (DFWM) experiments in room-temperature GaInAsP using a mode-locked color center laser.
Abstract: We report the first λ∼1.5 μm picosecond near‐band‐gap nonlinear absorption and degenerate four‐wave mixing (DFWM) experiments in room‐temperature GaInAsP using a mode‐locked color center laser. The temporal, spectral, and pump energy dependences of the nonlinear signals are investigated. Nonlinear absorption cross sections σeh as large as −5.7×10−15 cm2 are obtained from the pump probe results, while effective nonlinear cross sections σeff as large as 7.8×10−16 cm2 (corresponding to a steady ‖χ(3)‖∼3.8×10−3 esu for a 20‐ns relaxation time) are measured in the DFWM experiments.