Precise control of phase constant of optical guided-wave devices by loading Langmuir-Blodgett films

A Langmuir-Blodgett film is used as a cover layer of single mode waveguide to precisely control the phase constant of the guided-mode. The change of phase constant caused by the cover layer is evaluated by measuring the retardation between the two arms of the ion-exchanged glass waveguide Mach-Zehnder interferometer, a part of which is loaded by Langmuir-Blodgett films. A monolayer of cadmium stearate has varied the phase constant on the order of 10/sup -6/. This method can be used to adjust the phase difference or shift to tune the performance of guided-wave devices such as directional couplers and modulators.<
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