Abstract: An apparatus for growing single crystals of III-V compound semiconductors of the vapor pressure control type using a vertical puller characterized by dividing the surface area of a melt into two sections, covering one section with a liquid encapsulant while maintaining the other section in contact with the atmosphere of the vessel (furnace). The apparatus comprises a sealable vessel, an upper shaft, a lower shaft, a plurality of heaters, a crucible and a means for dividing the surface of the melt contained in the crucible. As a result, single crystals of III-V compound semiconductors having various excellent properties such as low impurity content (high purity), low dislocation density and the like maybe obtained.

Abstract: Disclosed is a method of making a huge elongated space of square or rectangular cross section under the ground. The outer shell of the huge elongated space is built in the form of integral arrangement of lateral shell-units having shielded passages therein. Such a huge underground space can be made without requiring any large-scale equipments on the ground. The huge outer shell can be made with accuracy and efficiency by skiving and jointing adjacent parallel lateral shell-units and by using selected lateral passage of shell-units to discharge the soil or mud removed in making the underground space.

Abstract: A process for growing single crystals of the III-V compound semiconductor is provided, which is the vapor pressure control method using a vertical puller and which is characterized by dividing the surface area of the melt into two sections, covering one section with a liquid encapsulant while remaining the other section in contact with the atmosphere of the vessel (furnace), and this process may be preferably carried out by using an apparatus which comprises a sealable vessel, an upper shaft, a lower shaft, a plurality of heaters, a crucible and a means for dividing the surface of melt contained in the crucible, and as a result single crystal of III-V compound semiconductor having various excellent properties such as low impurity content (high purity), low dislocation density, and the like may be obtained.

Abstract: A modified liquid encapsulated Czockralski method for growing a single crystal of compound semiconductor is disclosed. This method uses two vessels. An inner vessel is filled with an inactive gas, a gas of an element of group V and optionally an impurity gas. The inner vessel encloses a crucible containing compound semiconductor material, an encapsulant material, and optionally an impurity element. An outer vessel is filled only with the inactive gas. The total pressure of the inner atmosphere is equal to or higher than that of the outer atmosphere. The partial pressure of the gas of the element of group V is larger than the dissociation pressure of the element of group V near the melting point of the compound semiconductor.

Abstract: A method of making a holographic light guide comprising, in sequence, a substrate, a light guiding layer and a holographic recording layer that partially replaces the light guiding layer is disclosed. The substrate is made of a first bismuth sillenite group substance. The light guiding layer is made of a second bismuth sillenite group substance that has a higher refractive index than the first bismuth sillenite group substance and absorbs little of the light being guided. The holographic recording layer is made of a third bismuth sillenite group substance that has a higher refractive index than the first bismuth sillenite group substance and has a degree of photosensitivity.

Abstract: A hologram recording material comprises one of bismuth silicon oxide and bismuth germanium oxide, and Fe added to these material. The density of Fe is 10 p.p.m.

Abstract: An optical voltage and electric field sensor for detecting the voltage or electric field applied to a device made of a single crystal of bismuth silicon oxide (Bi.sub.12 SiO.sub.20) or bismuth germanium oxide (Bi.sub.12 GeO.sub.20) is disclosed. The device comprises a plurality of crystal plates stacked in a direction perpendicular to the propagation direction of light, each plate having only one dimension reduced to a very small size.

Abstract: A voltage and electric field measuring device using light as an operating parameter. An electro-optic crystal, a quarter-wave plate, and a polarization analyzer are arranged in that order in the direction of advancement of applied light. A voltage may be applied to the electro-optic crystal through electrodes arranged thereon. The electro-optic crystal belongs to a cubic system, such as bismuth silicon oxide or bismuth germanium oxide.