Abstract: A semiconductor laser having high efficiency of luminescence can be obtained by forming a spatial fluctuation of potential so that the potential differs from position to position inside a plane perpendicular to a current flowing direction and electrons and holes or excitons formed by a combination of them can be localized not only in the current flowing direction but also inside the plane perpendicular to the current flowing direction. More definitely, corrugations or ruggedness having a mean pitch of below 100 nm and a level difference of from 1/10 to 1/2 of the mean thickness of an active layer are formed on the surface of the active layer of the semiconductor laser.

Abstract: Optical information reconstructing apparatus comprising a disc having at least one surface on which groups of dots bearing information are concentrically or spirally arrayed, a mechanism for rotating the disc, a light source for projecting a light beam on the array of groups of dots, and at least one photodetector for detecting diffracted light waves from the groups of dots, characterized in that a semiconductor laser array is used as the light source and that the light emission is switched from one laser source to another in the laser array in tracking the information.

Abstract: A holographic device comprises a film for displaying a three-dimensional object as images, each of which is obtained as viewed in a respective one of a plurality of different directions, a phase plate for providing a light beam for illuminating each of said images of the film with an additional phase at random, a sampling grating for dividing a light beam from the phase plate into a plurality of small groups of light beams, a photosensitive material, and a slit for simultaneously radiating said light beam and a light beam having coherency therewith on each position of said photosensitive material in succession.

Abstract: A hologram apparatus comprises a rotary plane with a plurality of holograms concentrically or spirally arranged thereon, a light emitting source, and at least one photodetector for reading out reconstructed images of the holograms. During rotation of the rotary plane, the optical path of a light beam from the light emitting source is controlled, whereby the reconstructed images from the respective holograms are focused on the photodetector in succession. Some or all of the holograms are substantially oblong, and the long side and the short side of each oblong extend radially about the axis of the rotary plane and substantially orthogonally to the radial direction respectively.

Abstract: A hologram device carrying at least one hologram on a light sensitive medium in which the part of the light sensitive medium which carries the hologram thereon is impregnated with a laser active material.