New Patents

4782493 4783425

GAS DISCHARGE TUBE WITH HOLLOW CATHODE FOR METAL

VAPOR LASER

Nikola V Sabotinov, Margarita G Grozeva, Ivan R Angelov, Sofia, Bulgaria assigned to In- stitute PO Phisica Na Tvardoto Tyalo

This invention relates to a gas discharge hollow cathode tube for laser using metal vapors having a vacuum compact housing where an anode and a hollow spiral cathode are mounted connected to a source of excitation, the hollow cathode con- tains an active metal medium, having evenly dist- ributed apertures on the pipe’s upper inner part, and resistance wire fitted inside the hollow cathode supplied from an electric source. This apparatus avoids the disadvantages of a similar gas discharge tube having metal in the cylindrical cathode where the metal vapors enter the dis- charge zone uncontrollably, causing metal ac- cumulation in some zones which thus partially covers the laser tube aperture, and because the high-level ionic metal laser levels are not effic- iently excited as it operates under low voltages, it cannot be used for generation using easily fusable metals as the spiral cathode cannot be made of such metals. The invention also has im- proved stability and efficacy of the generation.

4783373

ARTICLE WITH THIN FILM COATING HAVING AN

ENHANCED EMISSIVITY AND REDUCED ABSORPTION OF

RADIANT ENERGY

Philip W Baumeister, Matthew Krisl assigned to Optical Coating Laboratory Inc

A coating useful for a solar cell is formed by con- current deposition of two materials, such as silicon dioxide and magnesium fluoride, on a substrate within a single vacuum chamber. The deposition is monitored to enable control of the ratio of the materials and the thickness of the coating. An alternative embodiment of a coating employs alternating layers of different materials which form pairs or periods, each having a very small optical thickness. By virtue of the coatings, emissivity is enhanced by suppression of the rest- strahlen reflectance and solar absorption is reduced by external reflection of the ultraviolet portion of the solar spectrum.

FABRICATION PROCESS OF SEMICONDUCTOR LASERS

Tadashi Fukuzawa, Yuichi Ono, Shinich Nakat- suka, Takashi Kajimura, Tokyo, Japan assigned to Hitachi Ltd

A p-GaAlAs cladding layer is exposed to the air if a groove of the form of a stripe is formed by chemical etching in an n-GaAs layer that serves as a current confinement layer on the p-GaAlAs cladding layer, the groove being so formed as to reach the cladding layer. The GaAlAs is oxidized so easily that an unstable degradation layer is formed on the surface thereof. To solve this problem according to the prior art, an undoped GaAs layer that serves as a cover layer is formed on the p-GaAlAs cladding layer, the n-GaAs layer is formed, and the etching is effected so that the undoped GaAs layer is simply exposed. The undoped GaAs layer is then heated in the MBE apparatus while being irradiated with the As molecular beam and is thermally etched. There- fore, the cladding layer is exposed in vacuum and the p-GaAlAs layer is formed thereon. However, this method is not suited for mass-production since the thermal etching is unstable and it needs the MBE apparatus of a very high degree of vacuum. Quality of the crystal decreases, too, due to the heating. This invention therefore pro- vides a fabrication process of semiconductor lasers in which the cover layer disappears due to interdiffusion of constituent elements that stem from the diffusion of impurities such as zinc ions in the undoped GaAs layer.

4787824

ROTATING LIQUID RING VACUUM PUMP

Michae Cole, Ipswich, United Kingdom as- signed to Genevac Limited

A method of and apparatus for pumping fluids wherein a rotating ring of liquid traverses a hol- low probe which has a surface aperture out of which the fluid to be pumped is sucked into the rotating liquid ring, wherein the fluid migrates to a collection region inside the rotating liquid ring, from where the fluid can pass to a fluid outlet, and wherein a gas which does not condense un- der the prevailing operating conditions is also fed to the collection region in order to assist throughput of the fluid being pumped.