Final Technical Report

Studies of Optical Beam Phase Conjugation and Electromagnetic Scattering Process.

R. W. Hellwarth

Published May 5, 1992• 0 citations

Abstract

In this project we have performed both experimental and theoretical studies of optical beam phase-conjugation and of electromagnetic scattering and propagation with intense optical fields. During the reporting period we have: (1) demonstrated that atomic vapors require fewer photons to perform optical wave mixing that any other medium examined to date; (2) sowed theoretically that a one-joule broadband optical pulse, whose carrier wavelength is one micron, can impart nearly one GeV energy to a charged particle; (3) established the stringent experimental upper limits on the hyperpolarizabilities of C60 and C70 molecules in solution; (4) made the first direct time-of-flight measurements of the drift velocity of photoexcited carrier in any photorefractive insulator (n- type Bi12SiO2O); (5) determined the difference between the complex polarizabilities of different trap levels in insulators; (6) made quantitative predictions and measurements of spatial harmonic content of photorefractive gratings; (7) developed and applied moving-grating diagnostic techniques to photoexcited carriers; (8) demonstrated an exception to the law of exponential attenuation of weak monochromatic optical beams in a homogeneous medium. Optical beam phase conjugation, Nonlinear effects, High power optical beam propagation, Photorefractive effect.

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Part I of this thesis describes the theoretical and experimental aspects of a new area in coherent optics known as phase conjugate optics. By using nonlinear optical mixing techniques, the complex conjugate of an arbitrary incident monochromatic wave can be generated. In particular, the theory of the degenerate four-wave mixing technique is presented. Experimental observation of phase conjugate wave front generation in a liquid crystal material (MBBA) is described. The ability of the conjugate wave front to correct for phase aberration is demonstrated. The quantum mechanical origin of the nonlinear third order susceptibility responsible for the four-wave mixing process is illustrated in an atomic system. Because of a finite memory time of such an atomic system, the electromagnetic waves taking part in the mixing process need not occur simultaneously. The applications of the phase conjugation process to real-time information processing and the characteristics of a phase conjugate resonator are discussed in detail. The ability of an optical fiber to confine the propagation of electromagnetic waves over a long distance and within a small cross sectional area implies that large optical intensities can be maintained over a long " interaction length even at moderate incident optical power. Part II of this thesis describes some third order nonlinear optical phenomena that have been observed under this condition. Especially, phase conjugation by degenerate four-wave mixing in a fiber has been shown to require significantly less pumping power. The theoretical and experimental studies of four-wave mixing in a liquid-filled fiber are presented. Extensive experimental efforts have been devoted over the last few years to the study of stimulated Raman scattering and the oscillation of the Stokes radiation inside fibers. A detailed theoretical treatment will be given here to describe these effects. The analysis shows that pump depletion due to the nonlinear process is very important in describing the stimulated Raman scattering in low loss fibers and is the dominant saturation effect in a fiber Raman oscillator. Finally, the implications of nonlinear optical phenomena to fiber optic communication will be mentioned.

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Introduction To And Applications Of Optical Phase Conjugation

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Mutually pumped phase conjugation in Kerr media

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