Showing papers on "Four-wave mixing published in 1978"

Degenerate four-wave mixing in absorbing media.

Abstract: Degenerate four-wave mixing in a two-level absorbing (or amplifying) system is treated, leading to a quantitative description of amplified reflection, oscillation, and phase conjugation.

Observation of amplified reflection by degenerate four-wave mixing in atomic sodium vapor.

Abstract: This Letter is the first report of the observation of amplified reflection and self-oscillation produced by degenerate optical four-wave mixing by using a resonantly enhanced Kerr nonlinearity in atomic sodium vapor. Phase-conjugated reflected waves with intensities 100 times greater than input-signal intensities were achieved with only 40-kW/cm2 pump intensity.

Spatial convolution and correlation of optical fields via degenerate four-wave mixing

Abstract: A nonlinear optical technique is described that performs, essentially instantaneously, the functions of spatial correlation and convolution of spatially encoded waves. These real-time operations are accomplished by mixing spatially dependent optical fields in the Fourier-transform plane of a lens system. The use of a degenerate four-wave mixing scheme eliminates (in the Fresnel approximation) phase-matching restrictions and (optical) frequency-scaling factors. Spatial bandwidth-gain considerations and numerical examples, as well as applications to nonlinear microscopy, are presented.

Continuous-wave backward-wave generation by degenerate four-wave mixing in ruby

Abstract: This is the first reported demonstration of cw wavefront conjugation by degenerate four-wave mixing in a solid. Conversion efficiencies of 3% for conjugate-wave generation were obtained in a ruby crystal using a cw argon-ion laser.

Narrow optical bandpass filter via nearly degenerate four-wave mixing.

Abstract: It is shown that a nearly degenerate four-wave mixing process is capable of yielding a real-time optical bandpass filter. The filter has a large field of view and is capable of providing an amplified bandpass. Moreover, the conjugate nature of the output field can be utilized to increase the signal-to-noise ratio of the device. For a 1-cm interaction length in a nondispersive medium, the optical bandpass at 5000 A can be varied from ~9 GHz down to the linewidth of the exciting laser.

High-efficiency pulsed 10.6-Mu m phase-conjugate reflection via degenerate four-wave mixing.

Abstract: We present the first reported observation in the infrared of nonlinear phase-conjugated reflection. This was achieved via degenerate four-wave mixing in polycrystalline germanium. The observation was facilitated by taking advantage of the counterpropagating (strong) waves internal to a pulsed CO2 laser cavity. The measured effective reflectivity was 2% with a 10-mm interaction length. This simple intracavity technique is generally applicable to any nonlinear material transparent at the wavelength of the laser into which it is inserted.

Image phase compensation and real‐time holography by four‐wave mixing in optical fibers

Abstract: It is proposed that real-time holography can be performed inside multimode fibers (or optical waveguides) using four-wave optical mixing. Of particular interest is the generation of complex-conjugate replicas of input fields for image transmission and compensation of propagation distortion. A theoretical analysis and a numerical estimate are presented.

Two-photon resonant four-wave mixing in atomic sodium vapour

Abstract: Using the 4d- and 5s-states of sodium, two different types of two-photon resonance enhanced four-wave mixing have been observed. In the first type 2vL =vIR +vpIR radiation near 2.34 μm and UV radiation near 320 nm has been detected. In the second typevP−vS =vL +vIR the UV radiation produced in the first parametric process acted as a pump for stimulated electronic Raman scattering via the 4p-state of sodium. Resonantly enhanced by the two-photon transition 3s–4s, radiation near 1.18 μm was produced in this scheme. The realisation of a tunable coherent IR source based on these four-wave mixing processes is discussed.

Effects of magnetic fields on four-wave mixing processes in atomic vapors.

Abstract: We have observed the effects of magnetic fields on four-wave mixing processes in atomic vapors. We have studied coherent vacuum-ultraviolet generation in Sr vapor via the process ω1 + ω2 + ω3 → ω4 in fields of up to 50 kG. Magnetic tuning of the resonances of the third-order nonlinear susceptibility χ(3) was used to modify the dependence of the sum-frequency output power on the generated wavelength.

EFFECT OF SPRAY MIXING ON TRAY EFFICIENCY I. One Dimensional Mixing

Abstract: The usual models for predicting the effect of liquid mixing assume a diffusion model as is reasonable for the foam and froth regimes Here a one-dimensional spray regime model is developed with finite spray “throw,” allowing for inlet and outlet conditions and the effect of spray mixing on tray efficiency is evaluated The extension to less restricted models is indicated