J. Janszky

Quantum statistics of the degenerate four-wave mixing process

Abstract A quantum mechanical treatment is given of the degenerate four-wave mixing process. The approximate Heisenberg equation of motion for creation and annihilation operators is solved taking into account attenuation and noise. The solution and the statistics of the modes are discussed both below and above the threshold condition.

Amplification of noise in the quantum theory of parametric processes

Abstract A quantum mechanical treatment is given of the acousto-optical parametric amplification processes in dielectric crystals when the signal acoustical and idler light waves are amplified in the presence of intensive optical pumping. The approximate Heisenberg equations of motion are found and solved for the creation and annihilation operators of signal and idler modes with due regard for the interaction of these modes with other light and vibratory modes of the crystal (“the thermostat”). It is shown that the thermostat influence results in noise and attenuation effects. These persistent noises are also amplified. If the pumping is not far above the threshold the persistent noises are more important than the initial ones.

Experimental data on the dislocation electric field in alkali halides

We investigated the properties of the dislocation photoconduction spectrum (DPS) in coloured alkali halide crystals. Based on theoretical and experimental results on the Stark-effect of the F-center caused by an external electric field, we obtained from the DPS experimental data on the magnitude of the internal electric field around edge dislocations in NaCl, KCl, KBr and KI crystals.

INTERACTION OF CHARGED PARTICLES AND LOCAL MODES.

Abstract By means of the coherent states technique the interaction of local modes of imperfections in alkali halide crystals with charged particles emerging from an ion avalanche is investigated. The energy obtained by an imperfection and that lost by a particle on unit way due to the interaction are evaluated. Part of the excess energy of the mode relaxes through phonon processes, a smaller part of the energy is emitted by the crystal on the local mode frequency. This way during the interaction the local mode emits infrared radiation; an estimate is given concerning the intensity of this radiation. This intensity has a well-defined peak at the velocity of particles being in resonance with the local mode frequency. Using different local centres some information can be obtained about the velocity distribution of particles inside the crystal during irradiation.

On the quantum theory of parametric frequency converter

A quantum mechanical treatment is given of the acoustooptic parametric conversion processes in dielectric crystals when the signal acoustical and idle light waves are transformed into each other in the presence of intensive optical pumping. The approximate Heisenberg equations of motion are found and solved for the creation and annihilation operators of signal and idle modes with due regard to the interaction of these modes with other light and vibratory modes of the crystal (“the thermostat”). It is shown that the thermostat influence results in noise and attenuation effects. These persistent noises are also converted from one mode into another and vice versa. Threshold conditions and asymptotic levels of noise are discussed.

Simultaneous effect of UV-irradiation and deformation

Abstract The present paper reports on experiments performed on X-ray coloured KC1 single crystals by means of dislocation photoconduction. This method makes use of the internal electric field developing in ionic crystals due to charged dislocations during their deformation. The effect of previous illuminations in the visible region on the photocurrent produced by VUV-light was also investigated, a memory effect and changes of the sign of the photocurrents were found under suitable conditions. It was shown that using visible light of high enough intensity the direction of the photocurrent produced by it also changes sign. The problems involved in the dislocation photoconduction method are discussed.

On the dislocation photoconduction and its application to study the deformation mechanism in ionic crystals

Abstract The photoconduction of the F-centres in X-ray coloured, bent KC1 single crystals has been investigated by using the electric field produced by displaced dislocations. It has been demonstrated that the photocurrent is composed of two components of opposite sign and of different relaxation time. The correlation between the presence of the negative current component and the shape of the photoconduction spectra was also investigated. It is concluded that there are two regions between the free surface and the mechanically neutral layer of the bent crystal in which the conductivities are different and the field is of opposite direction. It is proposed that these regions correspond to those studied by Whitworth. A procdeure will be shown to determine some parameters of these two regions and calculations will be presented in a simple model.