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The screened Coulomb-phonon quantum kinetics is applied to the twopulse excitation of femtosecond four-wave mixing (FWM). The time-resolved FWM shows, both in theory and experiment, a characteristic photon echo structure. From the analysis of the theoretical and experimental time-integrated signal, a dephasing time is obtained which varies with the inverse cubic power of the plasma density. Finally, FWM with coherent control yields in theory and experiment coherent plasmon-phonon mixed mode quantum beats. [ABSTRACT FROM AUTHOR]

The two-time screened Coulomb potential, as it results from a selfconsistent solution of the full Coulomb quantum kinetics after a femtosecond optical pulse, is described. The resulting potential is compared to femtosecond—resolved optical pump and THz—probe measurements including also the screening of the phonon-assisted carrier-carrier interaction. Excellent agreement between experiment and theory is found. Finally, the predictions of the Coulomb quantum kinetics for femtosecond four-wave mixing without and with coherent control are compared to corresponding experiments resulting in a density-dependent dephasing time and plasmon-phonon quantum beats. [ABSTRACT FROM AUTHOR]

The quantum kinetics for Coulomb interactions is derived. It is shown that the screened scattering potential depends on two time arguments, because screening is built up only after the carriers have been excited and begin to rearrange. The nonequilibrium screened Coulomb potential obeys an integral equation with a polarization due to carrier-carrier scattering. By a generalization of the equilibrium theory, a time-dependent plasmon-pole approximation is derived in order to illustrate the physical content of the complex formalism. [ABSTRACT FROM AUTHOR]

The full wealth of quantum kinetics can be tested by time-resolved femtosecond two-pulse spectroscopy either in the form of pump-probe spectroscopy or in the form of four-wave mixing. It is shown that pump-probe spectroscopy is amenable to follow the temporal evolution of the particle distributions. This is illustrated by calculations and experiments on the buildup of phonon cascades and on non-Markovian relaxation scenarios. Four-wave mixing, on the other hand, is shown to be well-suited for the study of quantum coherence and its dephasing illustrated by LO-phonon quantum beats. [ABSTRACT FROM AUTHOR]

The interband quantum kinetics is formulated for the scattering of the excited electrons and holes by a thermal bath of optical phonons. A series of approximations is developed for the required retarded functions, including a discussion of the band splitting introduced by a resonant intense laser beam. It is shown that the damping by LO-phonons can be described well with a hyperbolic secant. Finally strategies for the numerical solutions of the quantum kinetic equations are discussed. [ABSTRACT FROM AUTHOR]

The kinetics of the interband transitions in optically excited semiconductors is discussed and a brief historic review of this field is given. As an introductory example the free-carrier kinetics is formulated in terms of nonequilibrium Green functions, resulting in the semiconductor optical Bloch equations. [ABSTRACT FROM AUTHOR]

The theory of time-dependent transport phenomena in mesoscopic structures is formulated. Results are presented for a periodically modulated and a fluctuating resonant level model. A theory of noise is also developed. [ABSTRACT FROM AUTHOR]

Stationary transport properties of tunneling structures such as doublebarrier semiconductor heterostructures, superlattices, metallic nanowires, and Coulomb blockade structures are treated as examples for quantum transport through mesoscopic systems [ABSTRACT FROM AUTHOR]

The optical absorption of intense THz radiation in a two-band semiconductor is calculated. For this end the two-time interband susceptibility is expressed in terms of nonequilibrium Green functions. A number of special cases are calculated explicitly. The approach is generalized to include excitonic effects. Finally the theoretical predictions are compared to measured spectra. [ABSTRACT FROM AUTHOR]

As the device size shrinks, and the operating voltage is necessarily bounded from below, the electric fields inside the device must grow. In this chapter, we will address high-field transport phenomena in a systematic manner, and as a first step we study the general properties of free field-dependent Green functions which form the basic building blocks of the subsequent theory. In order to gain insight of how the general approach works, we next study a specific model of dynamical disorder, for which an analytic and exact theory can be developed. Finally, we give an extensive treatment of high-field transport in semiconductors, focusing in particular to the modifications one must make to the semiclassical Boltzmann equation. [ABSTRACT FROM AUTHOR]

The quantum transport equation in the linear limit is derived. For the particularly transparent case of electron-elastic impurity scattering contact is made with the Kubo formalism. Finally the weak localization corrections to the electrical conductivity are derived from the linearized quantum transport equation. [ABSTRACT FROM AUTHOR]

The quantum kinetic equation is in the slowly-varying center-of-mass coordinate approximation expressed in terms of the Wigner function. The collision integral is simplified by means of the generalized Kadanoff—Baym ansatz formulated in a gauge invariant way which respects causality. [ABSTRACT FROM AUTHOR]

A formulation of the quantum kinetic equation is given which is independent of the particular choice of the electrodynamic scalar and vector potentials. Because the evaluation of the collision term also requires the knowledge of the spectral Green functions, the gauge invariant equation for the retarded Green function is given as well. [ABSTRACT FROM AUTHOR]

We demonstrate how one recovers the Boltzmann equation from the quantum kinetic equation by a gradient expansion which holds if the variation of the center-of-mass coordinates is slow compared to that of the relative coordinates. Furthermore, it is necessary for this recovery that the spectral functions are sufficiently sharp. [ABSTRACT FROM AUTHOR]

The basic quantum kinetic equation which describes the time evolution of the particle propagator (or, the lesser Green function) G> is discussed in the formulations due to Kadanoff-Baym and due to Keldysh. [ABSTRACT FROM AUTHOR]

We introduce the concept of nonequilibrium Green functions which are ordered on a time contour - also called Keldysh contour - running from the remote past where the system was in equilibrium to the highest relevant time and back to the remote past. The resulting four Green functions are shown to be interrelated, but two of them, e.g., a spectral Green function and a kinetic Green function contain in nonequilibrium separate information in sharp contrast to the equilibrium situation. Using analytic continuation useful relations for products of Green functions are derived. [ABSTRACT FROM AUTHOR]

The second quantization for many-body systems is introduced. Within this formalism an elementary derivation of a non-Markovian quantum kinetic equation is given for the reduced density matrix. Next we review the equilibrium Green functions, including the dissipation-fluctuation theorem, the self-energy concept, and the perturbation expansion. [ABSTRACT FROM AUTHOR]

Various concepts for the numerical solution of the semiclassical Boltzmann equation are discussed, including an illustration of the use of a linearized Boltzmann equation and its eigenfunction expansion for a 2D electron gas. The numerical results for the linearized Boltzmann equation are compared with those of an ensemble Monte Carlo simulation of the Master equation. Finally the Boltzmann equation together with the Poisson equation is solved self-consistently for a spatially inhomogeneous electron gas in the relaxation time approximation. [ABSTRACT FROM AUTHOR]

We review some of the general properties of the semiclassical Boltzmann equation - not necessarily restricting ourselves to the dilute electron gas - paying special attention to its irreversible properties. [ABSTRACT FROM AUTHOR]

Several optical configurations for signal processing have been discussed. The ability to format the input signals to enhance the processing ability of the optical system has been emphasized together with the importance of the input transducer. Specific attention has been given to the use of the folded spectrum for high time-bandwidth signal processing and to the use of coherent optical techniques in radar signal processing. From a simple description of the relation between the input raster format and output folded spectrum and selected examples of the use of this system, the potential of this powerful technique should be apparent. The extensive use of the DKDP light valve in radar signal processing has also been summarized in such a manner that the basic input format was identical in all instances. Extensions of these techniques in radar and other signal processing applications to include matched filter correlation are the subject of current research. In several years these two systems promise to have major impact on signal processing since they utilize the real-time, parallel processing, high time-bandwidth, and correlation properties of a coherent optical processor. [ABSTRACT FROM AUTHOR]

This chapter reviews the applications of coherent optical correlation techniques to the measurement of parallax from stereo-photographs. A brief description of the various coherent optical correlation techniques is presented and their relative merits outlined. Two experimental prototype systems are discussed in detail and their test evaluation results are presented. The potentials of coherent optical processing techniques have been demonstrated and evaluated using real world aerial transparencies. It is reasonable to expect the widespread use of coherent optical processing techniques in different facets of photogrammetric data reduction. [ABSTRACT FROM AUTHOR]

This chapter has presented a brief review of optical image processing and some of its applications. The references presented here are only a sample of a copious source of available information in this field. It is recommended that the reader maintain an awareness of current literature because of the continuous developments being reported. Optical data processing is in its early stages of utility. Present demonstrations of optical processing are essentially one-of-a kind illustrations of feasibility. The authors believe that full utility of optical processing will be realized with the development of necessary peripherals for interfacing to digital control systems. The incoherent to coherent transducer with a laser beam recorder is one significant peripheral that, when fully developed, will permit practical use of the optical processor. Data throughput rates for some processing applications may then be increased significantly. On this basis, optical processing technology should be emphasized in the coming years. [ABSTRACT FROM AUTHOR]

This particular chapter is probably somewhat unusual because its purpose is a little different than some of the other contributions. We are not looking at how optical methods are being used to solve problems in a particular field even though there is a continued activity in the area of optical analogs to X-ray diffraction. The thesis has really been that there have been interesting pieces of work carried out by researchers actively engaged in optical analog techniques that can provide considerable insight to those working in the various aspects of diffraction and optical processing. I trust that this proves to be true. [ABSTRACT FROM AUTHOR]

We hope that the capsule remarks included on the Fourier transform, holography, interferometry, and correlation will serve as an adequate reference base for the succeeding chapters. The application areas selected are the major ones in which optical data processing has made and promises to make significant contributions. [ABSTRACT FROM AUTHOR]