GB1292016A - Metallic laser - Google Patents

Abstract

1292016 Lasers COMMISSARIAT A L'- ENERGIE ATOMIQUE 19 April 1971 [2 March 1970] 22857/71 Heading H1C In a tunable laser in which an active meta evaporated by an electric gas discharge between a cathode 10 and an anode 12 is ionized by the gas and produces stimulated emission, the cathode is in the form of a grooved block which is either formed wholly of the active metal, or consists of a different metal or an electrically insulating material having at least a part of the groove walls covered with a lining of the active metal. The gas may be helium and the metal cadmium. As shown in Fig. 1a, the grooved cathode 10 and a parallel rod anode 12 are housed in a glass gas tube 2 having Brewster end windows 4, the gas tube being located between resonator mirrors 6, 8 of which one is partially transmitting. The cathode is positioned so that the axis of symmetry of the groove coincides with the optical axis of the resonator. The groove has a depth greater than its width and may have its base enlarged and rounded as shown in Fig. 1b. Alternatively as shown in Fig. 2, the groove 20 may be formed of rectangular cross-section in a stainless steel block and have a cadmium lining 24 deposited on its base. Plural anodes 12 are also used, and the resonator consists of one plane and one spherical mirror 6, 8. The cathode may be cooled by a fluid passed through a duct 22, Fig. 1b, between inlet and outlet 14, 16, Fig. 1a. According to the Specification control of the anode-cathode voltage from a source 18 determines the wavelength of the stimulated emission, and frequency modulation can be obtained by varying the amplitude of the source voltage, e.g. for the reproduction of a colour image on a television receiver screen. The gas tube may include a control grid, and the cathode may be formed with a second groove oriented along a different axis to provide a dual output beam. The resonator mirrors may alternatively be within the gas tube.