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 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 generator for variable frequency submillimeter waves launches surface astic waves in piezoelectric material for generation of an associated acousto-electrical field. An electron beam is acted upon by the acousto-electrical field in a manner simulating the effect of an etched grating, resulting in an output frequency which may be varied by the variation of the acoustic wave frequency, or the velocity of the electron beam.

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.