Attention has been recently focused on a group of ferroelectric crystals that have the so called tungsten bronze structure. These materials actually contain no tungsten and are not bronze. They are transparent, contain NbO6 octahedra and have shown promise for applications in the Quantum Electronics field. The properties and uses of these ferroelectrics will be discussed in this paper.
The demonstrated suitability of ferroelectric crystals for efficient devices such as optical frequency doublers, optical parametric oscillators, and light modulators is convincing evidence of the importance of this class of materials for nonlinear optical applications. This paper considers two phenomena that arise from optical nonlinearities proportional to the square of the optical electric, field, in particular, second harmonic generation (SHG) and optical parametric oscillation (OPO). The optical interactions relevant to SHG and OPO are reviewed to determine the material properties required for efficient nonlinear optical devices. It is concluded that for these applications, ferroelectric type crystals have some inherent advantages over their nonferroelectric counterparts. A brief summary is given of some of the more significant experimental achievements involving cw as well as pulsed SHG and OPO. Progress in these areas is currently seriously hampered by a shortage of both high quality crystals known to be useful for these interactions as well as new materials for new wavelength regions.
The unique electrically variable light scattering and birefringence properties of certain hot-pressed ferroelectric ceramics are described. These properties depend on both grain size, which is controlled by the hot-pressing parameters, and composition. The ceramic electrooptic effects combined with localized switching capabilities are useful in various optical devices for information storage, processing, and display.
The technique of in-core measurements in nuclear reactors has become to play an important role to provide a variety of fundamental informations on reactor physics and reactor engineering and to improve the condition of economical operation of power reactors. The progress in the technique is reviewed for the following categories: (1) thermal and epithermal neutron spectroscopy in a reactor or in a critical assembly, (2) fast neutron spectroscopy in a reactor or in a critical assembly, (3) neutron flux measument in an operating power reactor, (4) process instruments in an operating power reactor, (5) in-pile dosimetry in a reactor. The emphasis is laid on the experiences at the Kyoto University Reactor, KUR.
Compressibility of polymer solution was measured by the ultrasonic interferometer at MHz range. Two kinds of compressibility, one of which corresponds to the compressibility of a random coil of polymer chain as a whole and the other which corresponds to' the compressibility of each segment, were calculated. The former is related to the dimensions of the polymer chain measured by the viscometric method, whilst the latter is inherent to each polymer. In the case of a binary copolymer, each component has its inherent compressibility under ordinary circumstances. In special solvents, however, one of the components becomes imcompressible.
Dislocations were introduced on the surface of a P/N-type Si solar cell by indenting it with a loaded diamond point and simultaneously annealing it. Increases of nonsaturable reverse current and of n value in forward characteristic, I0(e(qV/nkT)-1), were observed on the indented cells. In another type of cell, dislocations were introduced from the back surface by thermal annealing after the mechanically damaged layer was formed by the air blasting method. On this cell, small increase of n values and of reverse current were observed. The degradation of minority carrier life time and the proportional factors of defect introduction rate, Δ(1/τ)=1/τ7-1/τ0, of these dislocation-introduced cells were smaller than those of the normal cells under γ-irradiation. The interaction between defects and dislocations are considered from the isochronal annealing characteristics.
Some statistical considerations concerning the detection of informations regarding the fluctuation of light intensity from the view point of photon statistics have been made. It might be that the statistical values obtained from the observed photon distributions would not coincide with the true statistical values, and, the estimated parameters specifying the conditions of intensity fluctuation might not express precisely the real situations of the optical field when the number of times of the observation is limited within a finite number. In this paper some statistical methods of estimation of the parameters have been considered and the mean square deviation of the estimated parameters have been calculated in several cases. These considerations show that some estimators are unbiased and efficient estimators and that the mean squared deviations of the estimators are affected by the probability density function of the light intensity.
The propagation of a plane electromagnetic wave in a magnetoelectric (ME) medium is discussed with respect to the case where the (ME) suceptibility α can be expressed as a nondiagonal tensor. Concerning the propagation in the x direction, we obtain the theoretical result that the phase velocity changes with a reversal of propagating direction. We also examine the behavior of a plane wave which is normally incident on a perfectly conducting wall. The standing wave in this case shows the interesting behavior that the back-ward or progressive wave is due to the existence of ωα Further-more, the Fresnel's equations are analyzed with respect to the ME suceptibility constant, and these results show that, when the magnitude of the ME suceptibility exceeds a cirtain value, there exists only progressive or reflected wave in one direction and no wave in the other.
A highly sensitive fast neutron monitor using an organic scintillator is described. The pulse shape discrimination technique is adopted for the purpose of the gamma-ray rejection. Energy response of the monitor is improved by the use of the amplitude weighted counting method.