| 摘要 |
1,246,202. Modulating light. INTERNATIONAL BUSINESS MACHINES CORP. 30 April, 1969 [22 May, 1968], No. 21913/69. Heading H4F. The plane of polarization of coherent light from a source 3 is variably rotated by passing the light through an optically resonant medium 5 to cause self induced transparency, i.e. the phenomenon whereby a normally opaque medium becomes transparent to coherent light pulses having an electrical field strength above a threshold value, and causing a varying axial magnetic field to act on the light within the medium by way of an anomalously large Faraday effect. In the preferred embodiment, light pulsed by a modulator 4, e.g. a Pockels cell, and microwave pulses from a generator 2 are supplied synchronously to the medium 5 by means of a master oscillator 1. The group velocity of the microwave pulses is matched to the propagation rate of the light pulses through the medium, e.g. by feeding them to a slow wave helical structure. P.C.M. information is supplied to generator 2 and a polarization analyser may be placed after the medium 5 to intensity modulate the light. The source 3 may be, e.g. a solid state or gas laser, a parametric light oscillator or a giant pulse laser and may produce plane polarized light inherently, e.g. using Brewster windows, or incorporate a polarizing plate. Examples given are of a CO 2 laser with SF 6 as the medium 5, and a ruby laser 3 at liquid nitrogen temperatures with a ruby medium 5 at liquid helium temperatures. |
