| Summary: | Two high frequency, non-electro optic methods for modulating the intensity of a laser are examined theoretically and experimentally. The first modulation technique makes use of the Zeeman effect. Under an applied DC magnetic field, a splitting into two lines or three lines occurs. Modulation rates of 200 MHz have been proven possible with this technique. In the second technique, the properties of self phase modulation of a monochromatic light are explored. For a high intensity beam, the optical path of a beam can be altered due the dependence of the phase on intensity. Thus two coherent beams of light of different intensity can be made to constructively or destructively interfere even if the physical paths are identical. In a configuration called a nonlinear optical loop mirror, the output beam is amplitude modulated by linear variations in time of the total input power. A new design for a variable X-coupler, a key element of the loop mirror, is presented. Applications of high frequency modulators to test a theory of the AM-FM conversion of monochromatic light in fibers, to improve pulse rate control during target acquisition, and to high speed communications are discussed.
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