GB1095521A - - Google Patents

Abstract

1,095,521. Modulating light. WESTINGHOUSE ELECTRIC CORPORATION. Jan. 11. 1966 [Jan. 21, 1965], No. 1203/66. Heading H4F. To phase modulate a coherent light beam 2, Fig. 1, with a carrier signal itself modulated by an intelligence signal, a standing micro wave is generated in a cavity 4 at the carrier frequency by means of coupling loop 20, and electric field responsive refracting elements 10, e.g. Pockel's cells or cuprous chloride crystals, are aligned in the light path at intervals of half wavelength of the carrier and at the antinodes of the standing microwave for varying the effective velocity, i.e. phase, of the light beam in response to the alternating electric field from said standing microwave. The velocity of the microwave energy of the standing wave is made the same as the velocity of the light through the cavity and since the elements 10 are at half wavelength locations the phase deviation of the light beam produced in the elements is additive. Thus for a given deviation less power in the microwave frequency signal is required and the generated heat may be readily removed. The Pockel's cells or crystals 10 are positioned in waveguide 12 having ridges 14 and 16, Fig. 3, which enables the electric field to be concentrated in the region of the crystals. Dielectric sheets 22 and 24, Fig. 3, are disposed in the cavity 4 parallel to the light beam and are gang controlled for sliding movement for delaying the modulating signal to each crystal 10 a time equal to the delay incurred by the light as it passes through each crystal.