Showing papers on "Four-wave mixing published in 1981"
TL;DR: In this article, deegenerate four-wave mixing experiments have been performed using a liquid suspension of 0.234-μm-diameter latex spheres as the nonlinear medium.
Abstract: Degenerate four-wave mixing experiments have been performed using a liquid suspension of 0.234-μm-diameter latex spheres as the nonlinear medium. The measured effective optical Kerr coefficient, n2, is 3.6 × 10−3 (MW/cm2)−1. This is ~105× the value for CS2. Measured grating reflectivity, formation, and decay times are in reasonable agreement with a simple model assuming Rayleigh scattering and Brownian diffusion.
196 citations
TL;DR: Temperature mapping of the corona obtained from the linewidths (interpreted as pure thermal broadening), measured on the 90and 30-sec exposure interferograms, is shown in Fig. 4.
Abstract: This is seen clearly in Fig. 3, which enlarges this region of the interferogram. The magnitude and the direction of splitting (a shift towards shorter wavelength) indicate a line-of-sight approach velocity of -70 km/sec. Since the rest of the fringe is more or less undistorted, this is evidence of differential mass velocity for a portion of coronal gas relative to the rest of the coronal gas. Temperature mapping of the corona obtained from the linewidths (interpreted as pure thermal broadening), measured on the 90and 30-sec exposure interferograms, is shown in Fig. 4. A temperature inversion at a distance of -0.15 solar radius from the photosphere apparently occurs along many azimuths.
59 citations
TL;DR: Phase-matched four-wave mixing in sodium vapor with a helium buffer gas is carried out in a noncoplanar geometry and a theoretical interpretation of this effect caused by elimination of destructive interference between two coherent pathways is presented.
Abstract: Phase-matched four-wave mixing in sodium vapor with a helium buffer gas is carried out in a noncoplanar geometry. The directions of the four light beams remain nondegenerate even if all frequencies are equal. A sharp zero-difference frequency resonance in the intensity of the parametrically generated fourth beam by three incident beams is observed that is proportional to the square of the pressure of the buffer gas. A theoretical interpretation of this effect caused by elimination of destructive interference between two coherent pathways is presented.
50 citations
TL;DR: In this article, the third-order susceptibilities for a Doppler-broadened two-level system were calculated for four-wave mixing on the angle θ between the pump and signal fields, and the reflection coefficient was shown to have a narrow field of view that is inversely proportional to the ratio of the width to the homogeneous linewidth.
Abstract: Third-order susceptibilities are calculated for a Doppler-broadened two-level system. The dependence of four-wave mixing on the angle θ between the pump and signal fields is studied, and the reflection coefficient is shown to have a narrow field of view that is inversely proportional to the ratio of the Doppler width to the homogeneous linewidth. For the collinear geometry, θ = 0°, the frequency dependence of the nondegenerate case is analyzed and shown capable of yielding a real-time narrow-bandwidth optical filter whose bandwidth is limited by the homogeneous linewidth.
36 citations
TL;DR: The data show multiresonant behavior as a function of the pump-probe detuning at both low and high intensities, and five-peak structure is observed and is explained by the standing-wave modulation of the ac Stark splitting of the atomic levels.
Abstract: We have experimentally studied the effects of pump–probe detuning in nearly degenerate four-wave mixing. The data show multiresonant behavior as a function of the pump–probe detuning at both low and high intensities. At low intensities, the structure is the result of Doppler motion. At high intensities, five-peak structure is observed and is explained by the standing-wave modulation of the ac Stark splitting of the atomic levels.
34 citations
TL;DR: The operation of Mach-Zehnder and Michelson phase-conjugate interferometers is demonstrated and phase conjugation is obtained by degenerate four-wave mixing in thin films of eosin.
Abstract: The operation of Mach–Zehnder and Michelson phase-conjugate interferometers is demonstrated. Phase conjugation is obtained by degenerate four-wave mixing in thin films of eosin. High-visibility fringes are observed both in cw and pulsed modes of operation.
33 citations
TL;DR: This work reports the first known observation of amplified reflection through degenerate four-wave mixing at 10.6 microm, and reports the maximum reflectivity reported is 800% in p-type Ge.
Abstract: We report the first known observation of amplified reflection through degenerate four-wave mixing at 10.6 microm. Reflectivities of over 100% are reported in both n-type and p-type germanium at pump intensities of about 100 MW/cm(2). The maximum reflectivity reported is 800% in p-type Ge.
29 citations
TL;DR: The linewidth and intensity of the four-wave degenerate mixing signal in Na vapor have been observed as functions of He buffer-gas pressure with cw single-mode dye-laser beams, and a quantitative comparison with theory is made.
Abstract: The linewidth and intensity of the four-wave degenerate mixing signal in Na vapor have been observed as functions of He buffer-gas pressure with cw single-mode dye-laser beams. The width is independent of He pressure, and a quantitative comparison with theory is made. We also report the observation of a new effect, a four-wave mixing Raman-type resonance between two equally populated hyperfine levels.
29 citations
TL;DR: Two different configurations are indeed obtained and experimentally demonstrated that have, in the worst direction, spatial resolution of the order of 1 mm, with beam apertures comparable with those used in the standard collinear experiments and without the complicating requirement of two distinct pump beams.
Abstract: This paper contains a discussion of the relation between the angular distributions of the coherently emitted radiation and the angular distribution of the incident beams in a degenerate four-wave mixing experiment, when two of the input beams are derived from the same laser source. The objective of the discussion is to obtain beam configurations that permit the use of such spectroscopic techniques when good spatial resolution is required so that the conventional collinear phase matching geometry is inappropriate. Two different configurations are indeed obtained and experimentally demonstrated that have, in the worst direction (longitudinal), spatial resolution of the order of 1 mm, with beam apertures comparable with those used in the standard collinear experiments and without the complicating requirement of two distinct pump beams.
28 citations
TL;DR: In this paper, a pressure-induced extra resonance in four-wave mixing (PIER4) was observed using single-mode continuous-wave dye laser, which was verified by the theory of nonlinear susceptibility.
Abstract: We report observation of a pressure-induced extra resonance in four-wave mixing (PIER4 signal) using single-mode continuous-wave dye lasers. The narrow laser linewidth permits for the first time a quantitative verification of the frequency, intensity, and pressure dependence of the PIER4 signal predicted by the theory of the nonlinear susceptibility ${\ensuremath{\chi}}^{(3)}$.
28 citations
TL;DR: In this paper, phase conjugation of radiation from a KrF laser (249 nm) is reported using degenerate four-wave mixing in CS2 and in a variety of saturable absorbers.
Abstract: Phase conjugation of radiation from a KrF laser (249 nm) is reported using degenerate four-wave mixing in CS2 and in a variety of saturable absorbers. Dependence on input intensity and medium concentration is investigated. Reflectivities ≳ 2.5% have been measured. A thermal phase grating seems to be the mechanism involved.
TL;DR: The spectrum of degenerate four-wave mixing in Na vapor is shown to be purely dispersive for Rabi frequencies between the natural linewidth and the Doppler width.
Abstract: The spectrum of degenerate four-wave mixing in Na vapor is shown to be purely dispersive for Rabi frequencies between the natural linewidth and the Doppler width. This result is qualitatively explained by the fact that absorption saturates much faster than dispersion.
TL;DR: An ultrahigh-Q, tunable optical filter with a FWHM bandwidth of 41 MHz is demonstrated and degenerate phase-conjugation experiments in sodium suggest that a quantum efficiency of greater than unity can be attained on a cw basis.
Abstract: An ultrahigh-Q tunable optical filter with a FWHM bandwidth of 41 MHz is demonstrated. The filtering is produced by nondegenerate phase conjugation through four-wave mixing in atomic-sodium vapor. The filter is observed to have a maximum quantum efficiency of 4 x 10^-3. However, degenerate phase-conjugation experiments in sodium suggest that a quantum efficiency of greater than unity can be attained on a cw basis.
TL;DR: A degenerate four-wave mixing technique for measuring optical Kerr coefficients that permits discrimination between fast and slow (thermal) nonlinearities and reports results for a number of long-chain organic materials.
Abstract: We describe a degenerate four-wave mixing technique for measuring optical Kerr coefficients. This technique permits discrimination between fast and slow (thermal) nonlinearities. We report results for a number of long-chain organic materials.
TL;DR: Results of a computer model, which describes all resonant parametric and Raman processes involving frequencies up to fifth-order Stokes waves in a multiple-Raman-shifting amplifier using H(2), are reported.
Abstract: Results of a computer model, which describes all resonant parametric and Raman processes involving frequencies up to fifth-order Stokes waves in a multiple-Raman-shifting amplifier using H2, are reported. The model is primarily concerned with downconverting ultraviolet excimer laser wavelengths to the blue-green. Results for shifting the XeCl laser (308 nm) to the third Stokes wave (499 nm) are presented.
TL;DR: A phase-conjugate signal has been obtained in SF(6) with a peak reflectivity of 1.2 x 10(-3) by using a cw CO(2) laser operating on the P(16) line.
Abstract: A phase-conjugate signal has been obtained in SF6 with a peak reflectivity of 1.2 × 10−3 by using a cw CO2 laser operating on the P(16) line. The degenerate four-wave mixing spectrum exhibits a Doppler-free structure with 2-MHz resolution. When the reflectivity spectrum is compared with the saturated-absorption spectrum, matching peaks in the reflectivity spectrum are found over an 80-MHz bandwidth.
TL;DR: In this article, the first known demonstration of UV phase conjugation using degenerate four-wave mixing in 1-mm samples of CS(2) mixtures was reported. But, dilution of CS2 in several UV-transmitting solvents opened up a concentration-tunable (2450-2850 A) spectral window, allowing the optical Kerr effect to be utilized.
Abstract: We report the first known demonstration of UV phase conjugation. By use of a 15-psec, 2660-A pulse, 0.1% conjugate reflectivities were obtained through degenerate four-wave mixing in 1-mm samples of CS(2) mixtures. Although pure CS(2) did not exhibit the effect, dilution of CS(2) in several UV-transmitting solvents opened up a concentration- tunable (2450-2850 A) spectral window, allowing the optical Kerr effect to be utilized. Weaker phase conjugation at 2660 A was also observed in other Kerr media and in saturable absorber media.
TL;DR: In this paper, the impulse response of four-wave mixing was analyzed in the case where the two-photon term of the nonlinear susceptibility is dominant and it was shown that the reflected beam has only the character of perfect phase conjugation if the pulse length is longer than the medium length, and the latter is short compared to the characteristic distance.
Abstract: We present an analysis of the impulse response of four-wave mixing, in the case where the “two-photon term” of the nonlinear susceptibility is dominant. The nonlinear interaction itself will be considered to be steady state. The conditions of negligible pump depletion are considered first. It is shown that the reflected beam has only the character of perfect phase conjugation if the pulse length is longer than the medium length, and the latter is short compared to the characteristic distance of the problem. The “weak-pulse” approximation involving only two coupled equations is compared to the exact four-wave solution, when the medium thickness approaches the critical oscillation threshold. Finally, the stability and existence of steady-state solutions is analyzed for very long media (compared with the oscillation length).
Patent•
14 Dec 1981TL;DR: In this article, a device for producing a pair of synchronized intense 16 micron pulses in which stimulated rotational Raman scattering together with four wave mixing and pulse compression takes place in parahydrogen on an off-axis path between two spherical mirrors.
Abstract: A device is disclosed for producing a pair of synchronized intense 16 micron pulses in which stimulated rotational Raman scattering together with four wave mixing and pulse compression takes place in parahydrogen on an off-axis path between a pair of spherical mirrors.
TL;DR: An analysis is presented that predicts an exact equality of the reflectivities and identifies the parametric limitations.
Abstract: If a strong pump wave, with energy that is above threshold for stimulated Brillouin scattering, and a weak probe wave are incident into a nonlinear medium, then it has been shown by others that the reflectivity of the weak probe is equal to the reflectivity of the strong pump and that the probe is phase conjugated provided that the pump is phase conjugated. We present an analysis that predicts an exact equality of the reflectivities and identifies the parametric limitations.
TL;DR: In this article, the effects of the nonlinearity arising from the displaced emission spectrum are found and compared with the results of the two-level model of Abrams and Lind [ Opt. Lett.2, 94 ( 1978); Opt.Lett.3, 205 ( 1978)].
Abstract: Degenerate four-wave mixing in a separated absorption-gain system, such as that of an organic dye, is studied by using a four-level model. The effects of the nonlinearity arising from the displaced emission spectrum are found and compared with the results of the two-level model of Abrams and Lind [ Opt. Lett.2, 94 ( 1978); Opt. Lett.3, 205 ( 1978)]. A nonsymmetric saturation behavior over the width of the absorption line is shown to exist that can be detrimental to the phase-conjugate reflectivity. Otherwise, minor differences are seen from the two-level case.
TL;DR: It has been found that phase mismatch provides a window factor to the reflectivity that masks the frequency spectrum of the medium and that the line profile depends on the geometrical configuration of the three interacting beams.
Abstract: Backward nearly degenerate four-wave mixing close to the atomic resonance line has been investigated experimentally. It has been found that phase mismatch provides a window factor to the reflectivity that masks the frequency spectrum of the medium and that the line profile depends on the geometrical configuration of the three interacting beams. The capability of obtaining an optical bandpass filter with nearly degenerate four-wave mixing has also been demonstrated experimentally.
TL;DR: In this paper, the formulation of phase conjugation via nondegenerate four-wave mixing in a Doppler-broadened resonant medium is generalized to include non-enerate pump frequencies.
TL;DR: In this article, it was shown that the reflected phase-conjugate pulse and the incident signal pulse have areas related by the same equation relating field amplitudes in steady state.
TL;DR: In this article, the theory of nondegenerate four-wave mixing is described for the case wherein the counter-propagating pump waves are in two-photon resonance with the nonlinear medium.
TL;DR: In this article, the degenerate four-wave mixing and phase conjugation near the band edge of direct-gap semiconductors were discussed and it was shown that the reflectivity for conjugate waves is enhanced in the vicinity of band edge.
Abstract: We discuss degenerate four-wave mixing and phase conjugation near the band edge of direct-gap semiconductors and show that the reflectivity for conjugate waves is enhanced in the vicinity of the band edge. We also compare the quantum-mechanical results with the classical Drude model.
TL;DR: In this article, four-wave mixing with two circularly polarized counter-propagating waves inducing a helical birefringence structure can be used to measure a number of material parameters of a liquid crystalline medium.
Abstract: Four-wave mixing with two circularly polarized counter-propagating waves inducing a helical birefringence structure can be used to measure a number of material parameters of a liquid crystalline medium. Application to a cholesteric substance is particularly interesting. A resonant effect is expected when the induced helix has a pitch coinciding with the natural helical pitch of the medium towards the isotropic → cholesteric transition. Field-induced shift in the transition temperature is also expected.
TL;DR: In this article, a theoretical analysis of four-wave mixing in the active medium of a laser whose radiation wavefront is to be reversed is presented, where explicit allowance is made for changes in the amplitudes of the pump waves as a result of their amplification during propagation in an active medium.
Abstract: The two-level approximation is used to make a theoretical analysis of four-wave mixing in the active medium of a laser whose radiation wavefront is to be reversed. Explicit allowance is made for changes in the amplitudes of the pump waves as a result of their amplification during propagation in the active medium. Both the completely degenerate case, when the frequencies of all four waves are the same, and the case of a small detuning of the signal wave frequency relative to the pump waves are considered. For the completely degenerate case a system of reduced equations allowing for saturation of the inversion was solved by computer using an iterative method. It was found that, under optimum conditions in the saturation regime, the power of the wave reflected from a four-wave mixer may be higher than that of the signal wave.
Journal Article•