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20 September 1996 Poled fiber devices for electro-optic modulation
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Electro-optic modulators and switches are important components for photonic systems. Existing technologies (such as lithium niobate) have significant drawbacks in terms of coupling losses to fiber, photorefractive damage and cost. Silica, especially fiber, based devices would be ideal; unfortunately silica, being centrosymmetric, has no intrinsic bulk electro-optic characteristics. However an electro-optic coefficient can be induced by silica by poling. By thermal poling, an electro-optic coefficient of around 1 pm/V has been produced in bulk silica; whilst scientifically interesting, this is insufficient for practical devices, especially as the values for fiber are much smaller. Recent work on UV excited poling has produced values around 6 pm/V in fiber; sufficient to realize fiber devices a few centimeters long, requiring only a few volts for switching. To perform UV-poling, optical fiber with internal electrodes is produced by milling holes into the fiber preform, close and parallel to the core, and then pulling at sufficiently low temperature to avoid closure of the holes into which the fine wire electrodes are subsequently introduced. A voltage is applied to the electrodes to produce a strong electric field (approximately 100/V/micrometers ) in the fiber core which is also exposed to UV laser radiation. After removal of irradiation and field an electro-optic coefficient of around 6 pm/V is measured. By applying a modulating voltage to the internal electrodes this electro-optic coefficient may be used to effect phase or polarization modulation (and amplitude modulation in a suitable structure). Furthermore, by periodic UV-poling, electrically tunable in-fiber Bragg gratings may be produced. Details of the fiber and device geometry, the processing conditions, the measurement techniques, the device performance and potential applications of this exciting new technology will be presented.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Simon C. Fleming, Danny W. Wong, Hugh Inglis, Wei Xu, Takumi Fujiwara, and Peter Hill "Poled fiber devices for electro-optic modulation", Proc. SPIE 2893, Fiber Optic Components and Optical Communication, (20 September 1996);

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