The enhanced Faraday effect in gases for optical frequencies near absorption lines provides a basis for modulating a light beam. In the present study, incident radiation consisting of the Zeeman <i>s</i> components of the <i>D</i> lines of sodium passed through a polarizer to the Faraday cell, which employed saturated sodium vapor at approximately 240°C as an optical medium. Rotation of the plane of polarization of radiation traversing the cell was modulated at frequencies as high as 698 Mc/sec. On the basis of cw modulation studies, there appears to be no reduction in the integrated time-varying Faraday effect for frequencies as high as 265 Mc/sec; this frequency is 1100 times the Larmor frequency in the magnetic fields involved and 26 times the natural linewidth. There was no evidence of any reduction in frequency response for pulsed modulation at 698 Mc/sec.
BERNHARD M. SCHMIDT, JOHN M. WILLIAMS, and DUDLEY WILLIAMS, "Magneto-Optic Modulation of a Light Beam in Sodium Vapor," J. Opt. Soc. Am. 54, 454-455 (1964)