Sputter deposited piezoelectric fiber coatings for acousto-optic modulators

All-fiber optical phase modulators were fabricated by coating standard telecommunication optical fibers with thin films of piezoelectric ZnO. Piezoelectric optical fiber coatings of PbZrxTi1-xO3(PZT) were also produced, and the actuation capability necessary for making optical fiber modulators is demonstrated. Both the ZnO and the PZT fiber coatings were deposited by reactive direct current magnetron sputtering of metal targets. The geometry of the sputtering system, fiber rotation, and reactive sputtering processes that result in sufficiently high deposition rates for deposition of axially symmetric coatings between 0.5 and 7 mu m thick were studied. Two types of piezoelectric fiber optic modulator structures, Cr/Au/ZnO/Cr/Au and Ti/Pt/PZT/Au, are currently being investigated. Results on crystalline phase formation, microstructure, and piezoelectric and optical behavior of the coated optical fiber devices are presented. Impedance and phase angle measurements are used to demonstrate how device geometry affects the resonance response of ZnO coated devices. Interferometric measurements have shown that the ZnO-based modulators can produce optical phase shifts as high as 0.70 rad when the modulator is driven at the 196.5 MHz fiber radial resonance. (C) 1996 American Vacuum Society.