GB1054792A - - Google Patents

Abstract

1,054,792. Lasers; cathode-ray tubes. CSFCOMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. July 8, 1963 [July 6, 1962], No. 27025/63. Headings H1C and HID. In a laser situated in an evacuated envelope the pumping energy is supplied by an electron beam which is directed on to the solid laser material. Modulation of the electron beam effects modulation of the intensity of the generated light beam. As shown in the embodiment of Fig. 4 in which the apparatus is enclosed in an evacuated envelope 50 the lasing element comprises a number of parallel filaments 1 of a glass including 1 % of ytterbium or meodynie which are placed on a metal plate 4 acting as an anode for the electron beam from gun 2. Plates 31-32 deflect the beam along the fibres 1 and plates 21-22 deflect the beam normal to the longitudinal axis of the fibres so that when the alternating current generators 6, 5 are connected respectively to the two sets of plates the filaments are swept by the beam to cause uniform excitation of the electrons of the lasing material. The radiation produced by stimulated emission is propagated along the surfaces of the lasing elements as a surface travelling wave normal to the electron beam. In the apparatus of Figs. 5 and 6 (not shown) two semi-transparent mirrors 7, 8 are positioned at the ends of the filaments and transform the stimulated emission into a standing wave which propagates outwardly of the envelope. Cooling of the plate 4 is achieved by bath 10 of liquid nitrogen. A lens may be situated outside of the structure to deflect the output light or the ends of the filaments themselves may be bent. A flat beam and a single pair of deflecting plates is used. In another arrangement all the filaments may be excited simultaneously by using an undeflected and unconcentrated beam.