Abstract: French horns with four finger valves and one change horn valve, instead of the standard three finger valves and one change horn valve enable play in twelve keys, as well as twelve tones. Point and dimple connections between key levers and rotary valve string bars provide smooth translation of the string bars and smooth rotation of the rotary valve hubs. Screw-on mouthpieces and mouthpipes have smooth identical inner diameters to avoid the airstream disrupting steps of conventional push-in mouthpieces. Cork block mountings between the tubes, valves and slides instead of the standard soldered metal mountings avoid transmission of vibrations between the tubes. Hand straps steady the French horns instead of the usual finger hooks.

Abstract: A device which uses a light signal to control the amplification of light is disclosed. Optically active ions in a laser material are pumped to an intermediate energy state by light of a first frequency, and thereafter pumped from the intermediate energy state to an upper energy state by light of a second frequency. Lasing occurs when the optically active ions fall back to the intermediate energy state. When the intensity of the light of the first frequency is below the threshold pumping level, no laser action can occur even though the intensity of the light of the second frequency is above its threshold pumping level. Thus a large output power can be controlled by a small input power.

Abstract: Improvements in Praseodymium solid state YLF lasers operating in the blueeen spectral region at room temperature and providing short pulses useful for underwater communication and detection systems. A dye laser with a narrow spectral output matched to the absorption spectra of the solid state laser is provided as a laser pump. The Pr doped YLF crystal of the solid state laser is physically oriented so it can be longitudinally pumped by light polarized parallel to the c-axis of the crystal, and the solid state laser is equipped with special spectrally selective mirrors. The foregoing and other modifications of prior Pr solid state laser systems provide increased efficiency and power output.

Abstract: A high efficiency, high power blue-green laser capable of providing short lses useful for underwater communication and detection systems. To provide the desired blue-green lasing, a solid state laser is pumped by a matched high-efficiency laser having a relatively long duration output pulses. Q-switching of the solid state laser is used to shorten the duration and increase the peak power of the pulses. Material found especially useful for practice of the invention are Holmium.sup.+3 and Praseodymium.sup.+3 as the solid state laser and a dye laser pumped by a mercury capillary lamp as the pumping laser.

Abstract: A Nernst lamp is used as the pumping means for a solid state laser. The l materials are selected so that the light energy emitted is essentially concentrated in the relatively narrow pump region of the absorption spectrum of the laser crystal. The input power in to the laser is equivalent to that of much higher power lamps operating over a much wider spectrum.