The faraday effect useful force available for driving end of the optical system for the blocking of a light transmitter against the incidence of the reflected rays, and application in the case of a laser amplifier

摘要

1494001 Controlling light COMPAGNIE GENERALE D'ELECTRICITE 11 March 1975 [12 March 1974] 10149/75 Heading G2F [Also in Division HIC] An optical isolator comprises a number of plates 1-3, 6-10 exhibiting the Faraday effect and disposed in series on an axis 25 such that in the presence of a magnetic field B of predetermined amplitude and direction, a linearly polarized beam 20 travelling in the transmission direction is incident on each plate at substantially the Brewster angle and with a polarization direction in the respective plane of incidence (i.e. for plates of identical thickness and Verdet constant subjected to the same field B as shown, each plate is equally inclined to the axis 25 and is rotated about the axis by the Faraday rotation angle relative to the preceding plate), the number of plates, their thickness and material, and the magnetic field B being selected such that the linear polarization direction is rotated by 45 degrees between the first and last plates. Beams propagating in the opposite direction may be considered to be composed of linear polarizations parallel and normal to the plane of incidence at plate 10. The normal polarization is strongly reflected at plate 10, and less strongly at following plates. The parallel polarization is increasing reflected by plates 9 to 1 as its polarization vector moves increasing out of the plane of incidence. As particularly described 10 plates are used and a coil 30 provides the field B. In a modification, Fig. 3 (not shown) alternate plates are rotated by 180 degrees about the line 25 whereby the incident and sintering beams may be parallel to the axis 25. A high power laser may comprise a laser generator, a number of amplifiers, and the isolator in series. By forming the plates of an active material such as neodymium doped glass and providing a flash or other pumping device, the isolator may also function as the last amplifying stage, Fig. 4 (not shown).