Infrared and Visible Laser Modulation using Faraday Rotation in YIG

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Abstract
Faraday rotation in YIG has been employed to modulate 3.39‐μ radiation in a helium‐neon laser. YIG has sufficient transparency at this wavelength to permit placement within the optical cavity. Modulation at 13 Mc/sec corresponds to the round‐trip time 2L/c of photons in the cavity, and with the lasing condition, mode locking is observed with a spiked output beam similar to effects previously reported for lasers at 6328 Å. By the use of prisms and separate mirrors, lasing can occur simultaneously at 3.39 μ and 6328 Å, where modulation effects in the 3.39‐μ beam are transferred to the visible 6328‐Å beam. A variety of effects in the visible beam are observed, depending on the state (lasing or superradiant) of the 3.39‐μ beam; in particular, ``spiking'' or its opposite may be induced in the visible beam.