Abstract: A laser host material LuLF (LuLiF.sub.4) is doped with holmium (Ho) and thulium (Tm) to produce a new laser material that is capable of laser light production in the vicinity of 2 .mu.m. The material provides an advantage in efficiency over conventional Ho lasers because the LuLF host material allows for decreased threshold and upconversion over such hosts as YAG and YLF. The addition of Tm allows for pumping by commonly available GaAlAs laser diodes. For use with flashlamp pumping, erbium (Er) may be added as an additional dopant. For further upconversion reduction, the Tm can be eliminated and the Ho can be directly pumped.

Abstract: A method and apparatus for transmitting laser signals through fog, in which a laser signal directed into the fog is amplitude modulated at one or more resonant frequencies of the water droplets forming the fog at such strength as to cause the droplets to burst, thereby decreasing the scattering of the laser signal and increasing the transmission of this signal through the fog.

Abstract: A diffraction radiation generator in which a ribbon electron beam is directed over a diffraction grating within an open resonator at a selected velocity to generate coherent radiation. After passing through the open resonator, the ribbon beam is directed through aligned slits in two or more conductive elements to a collector. Progressively negative voltages relative to the grating voltage can be applied to the elements and the collector to decelerate the electrons forming the ribbon beam and thus minimize heating of the collector and increase the operating efficiency of the generator. Also, the elements and the collector can be utilized to analyze the ribbon beam.

Abstract: A crystalline bar is doped with a rare earth. The bar is transparent to ration, such as from a laser, at a light wavelength which excites the rare earth ions in the bar and the light is modulated at the frequency at which the bar mechanically resonates.The excited ion decay radiatively by light or non-radiatively by phonons. As the phonons decay, they excite the bar to resonate mechanically. The mechanical resonance may be coupled by a piezoelectric material and measured to give information respecting the phonon activity of the excited rare earth ions.

Abstract: The device of the invention comprises a body of dielectric material having a metallic surface on one portion thereof. An electron beam is passed adjacent a second portion of the dielectric body in order to generate electromagnetic radiation in the dielectric. A feedback loop is provided to improve the coherence of the radiation output.

Abstract: A high frequency electromagnetic wave generator is disclosed which comprises an electron gun which directs an electron beam through a region generally adjacent a diffraction grating. The grating cooperates with an opposed reflecting surface to produce a standing electromagnetic wave. The reflector comprises a highly reflective dielectric coated mirror. Supporting means for the diffraction grating may also comprise a reflective dielectric surface.

Abstract: A method and apparatus for determining aerosol size distributions, in which he droplets of an aerosol region are placed in an amplitude modulated electric field, which produces resonant elongation and contraction of particularly sized droplets, in the form of mechanical oscillations, depending on the modulating frequency of the modulated electric field. A light beam is directed against the oscillating droplets and scattered thereby, with the intensity of the scattered light beam varying as a result of the changing reflection surfaces presented by the oscillating droplets. Differently sized drops are sequentially resonantly oscillated by selectively varying the modulation frequency of the electric field, with the varying intensity of the oscillating droplets at each modulation frequency yielding the size distribution of a given aerosol.

Abstract: A rare earth semiconductor laser is disclosed comprising a semiconductor erial of the type Ln.sub.2 TX.sub.5 where Ln is a rare earth element, T is zirconium or hafnium, and X is sulfur or selenium. The semiconductor contains neodymium as a dopant rare earth ion and can be made to lase by applying an electric voltage.

Abstract: A method and apparatus for controlling a chemical reaction by heterogeneous catalysis, in which a surface acoustic wave (SAW) is propagated along a surface of a piezoelectric element in contact with liquid or gaseous substances to be chemically reacted, to thus generate an electric field at the surface of the element which initiates and sustains the desired reaction. The catalysis rate can be varied by varying the frequency and/or intensity of the surface acoustic wave. The surface of the element may be coated with a very thin film of a catalytic group 8 metal which can be penetrated by the SAW electric field. In such an embodiment, normal catalysis proceeds via chemisorption, and the SAW element field acts to increase the catalysis rate.