Abstract: A compact pulsed optical source of near to ultraviolet wavelength energy adapted to be connected to an external power source. The optical source includes a device for emitting photons, apparatus for transforming photons into photoelectrons, apparatus for multiplying the photoelectrons, a lens, a phosphor coated anode, circuit apparatus for providing a pulsed electric signal and first and second biasing apparatus. The emitting device impinges photons on the photon transforming apparatus which accelerates electrons to the multiplying apparatus as pulses are received from the circuit apparatus which relates the multiplying apparatus to the transforming apparatus. With each pulse, a cloud of electrons is emitted from the multiplying apparatus and excites the phosphor coated anode thereby causing optical emission.

Abstract: A high efficiency UV responsive negative electron affinity photocathode with the long wavelength cutoff tunable over the wavelength from .about.200 to .about.300 nm based on Al.sub.x Ga.sub.1-x N. Negative electron affinity photocathodes for sharply enhanced photoemission yield can be formed by applying a layer of cesium to the surface of Al.sub.x Ga.sub.1-x N for which the Fermi energy level is appropriately positioned.

Abstract: A method of preparing a UV detector of Al.sub.x Ga.sub.1-x N. Metal organic chemical vapor deposition (MOCVD) is utilized to grow AlN and then Al.sub.x Ga.sub.1-x N on a sapphire substrate. A photodetector structure is fabricated on the AlGaN.

Abstract: An optical smoke detector having a smoke sensing chamber comprising a point source of light mounted on the middle of a photodetector, the source of light transmitting in a forward direction and away from the photodetector and further having the point source of light located at the center of curvature of a spherical reflector. During normal standby periods when there are no smoke particles in the chamber to scatter the light, the light is transmitted to the spherical reflector and reflected back to the source without falling on the photodetector. In the presence of smoke the light is scattered and falls on the photodetector to indicate the presence of the smoke.

Abstract: Anomalously large photoresponse to radiation of energies between about 2.8 eV and about 3.8 eV has been observed in certain gallium phosphide photodetectors having an "as-grown" surface. This photoresponse is believed to be due to the low density of recombination centers in the as-grown surface.