Recent works on crystallographic, electrical and optical properties of the ternary compounds with chalcopyrite structure (II-IV-V2 and I-III-VI2 type) are reviewed. These compounds of II-IV-V2 and I-III-VI2 type are the nearest analogues of the well known III-V and II-VI compounds, respectively. Crystal growth techniques and general features of the band structures are also described.
Functions of optical lenses have changed with development of lasers and it becomes necessary to know their focal lengths more accurately. In an optical system of hologram memory, for example, it is necessary to know the focal length with more than a 4th-order precision which is hardly possible with any of the conventional methods. This paper presents a new method for measuring focal lengths by using the telecentric system and by measuring the inclination of an incident narrow beam, and the distance between a deflected beam and the optical axis. It has several features; (1) simple in principle (2) the use of a laser beam (3) no need to observe images. Application of this method to a ƒ=300 mm lens is discussed and it is verified theoretically and experimentally that measurement up to about a 5th-order precision is possible.
Investigation has been made of the stabilization of the second harmonic wave (5320Å) of Nd3+: YAG laser used a commercial Ba2NaNb5O15 crystal. A well stabilized second harmonic wave was obtained 1) by stabilizing the output power of the fundamental wave (1. 064μ) within one percent per hour, and, 2) by controlling the fluctuation of the crystal temperature within 0. 05°C. In order to utilize the second harmonic wave as a Raman source, it was necessary to control the temperature of the Ba2NaNb5O15 crystal at phase matching temperature within 0. 08°C in comparison He-Ne laser of which the output stability is 5 percent per hour. The characteristics of the second harmonic wave were compared with those of the He-Ne laser. By using this stabilized second harmonic wave, the resonant Raman scattering phenomena of ZnTe have been measured.
A hologram conversion technique by a computer method is proposed and an experiment to convert Fresnel-transform holograms into Fourier-transform holograms is conducted. A photographically recorded acoustical hologram constructed with a 15 kHz sound-wave is sampled with 64×64 sampling points and quantized into 5 levels for numerical processing. The hologram conversion is done by calculating the product of the Fourier spectra of the Fresneltransform hologram with a propagation function. The calculated Fourier-transform hologram is displayed by an X-Y plotter or a line printer and reduced photographically for optical image reconstruction. Images are reconstructed by performing the Fourier transform of the converted hologram in a suitable optical Fourier transform configuration. Some discussions on this numerical hologram conversion technique are conducted with reference to the experimental results.
Holographic storage properties, such as writing, reading out, erasing and persistence, were investigated in single crystals of Rh-doped LiNbO3. Thermal annealing in an oxygendeficient atmosphere and/or Cu-doping by thermal diffusion were found to improve optical sensitivity remarkably. The Cu-diffused layers fabricated in Rh-doped LiNbO3 are quite effective to high-speed optical writing and erasing, and, at the same time, do not reduce the persistence of holograms to any appreciable extent. Similar effects were found with an oxygendeficient Rh-doped LiNbO3. However, the persistence of the stored holograms exhibited a two-step decay behavior and its initial decay was remarkable. These facts indicate the co existence of two types of impurities; i.e., one which improves photo-sensitivity but reduces persistence, and the other which improves persitence only. In our case, the former impurity islikely to be Cu or oxygen-deficiency and the latter to be Rh