GB1043128A - Laser system - Google Patents

Abstract

1,043,128. Lasers. RADIO CORPORATION OF AMERICA. April 3, 1964 [April 15, 1963], No. 13918/64. Heading H3B. A laser output is amplitude modulated by applying a variable magnetic field to the solid laser active medium, which medium when excited below the laser threshold level produces a fluorescent line the width of which is not greater than the longitudinal cavity mode spacing of the laser resonant cavity. As shown in Fig. 1, the laser active medium 12 is optically pumped by a xenon flash tube and due to a homogeneous magnetic field applied by coil 20 laser action takes place between the Zeeman sublevels of two energy levels of the system. In addition to the homogeneous field a signalcontrolled inhomogeneous field is applied to the laser medium by coil 24 positioned at one end of the laser, so that the line width of the laser output is broadened, Fig. 5 (not shown). Since 'the pump power level required for laser operation is proportional to the fluorescent line width, variation in line width varies the amplitude of the output beam 22 and if the pump power is adjusted to be just above the threshold level of the laser before application of the inhomogeneous field then the laser output is switched off when the line is broadened sufficiently. In a second embodiment, Fig. 6 (not shown), coil 24 of Fig. 1 is omitted and a signal source is connected to coil 20. By varying the amplitude of the magnetic field the laser frequency is modulated in the active medium so that as the light output frequency changes the resonance conditions of the cavity determined by mirrors 16, 18 are satisfied or not satisfied and the output beam modulated in amplitude.