Fabrication and structural analysis of ZnO coated fiber optic phase modulators
- PDF / 493,283 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 0 Downloads / 176 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Fabrication and structural analysis of ZnO coated fiber optic phase modulators G. R. Fox and N. Setter Ecole Polytechnique F´ed´erale de Lausanne, Laboratoire de C´eramique, Lausanne, Switzerland, CH-1015
H. G. Limberger Ecole Polytechnique F´ed´erale de Lausanne, Laboratoire d’Optique Appliqu´ee, Lausanne, Switzerland, CH-1015 (Received 17 March 1995; accepted 1 December 1995)
Fiber optic modulators were fabricated by coating optical fibers with electrode and piezoelectric ZnO layers. The techniques of piezoelectric fiber optic modulator (PFOM) fabrication are presented, and the microstructure and crystallographic texture of the coatings are analyzed. In order to produce thick (approximately 5 mm) ZnO coatings, it was necessary to study the reactive dc magnetron sputtering process in O2yAr gas mixtures under conditions close to the transition between an oxidized and nonoxidized Zn target surface. In situ quartz crystal microbalance measurements of the deposition rate revealed thee distinct regions in the deposition rate (R) vs oxygen partial pressure (PO2 ) behavior, at constant total pressure, for sputtering under conditions that provided an oxidized Zn target surface. Additionally, a transition between oxygen and argon dominated sputtering as observed by varying the sputtering pressure while maintaining a constant PO2 . The transition between oxygen and argon dominated sputtering influences R to varying extents within the three R vs PO2 regions for an oxidized target surface. Correlations among the cathode current and voltage, deposition rate, and gas flow rate are presented to give a better understanding of the reactive sputtering processes occurring at the oxidized Zn target surface. Sputtering conditions optimized for a high ZnO deposition rate were used to produce k001l radially oriented ZnO fiber coatings for PFOM devices that can produce optical phase shifts as large as 0.38 radyV.
I. INTRODUCTION
Piezoelectric coatings on optical fibers provide a method for modulating the strain within a section of fiber. Straining a fiber changes the fiber dimensions as well as the fiber refractive index, due to the photoelastic effect. Modulation of the fiber length and refractive index can be used to induce a phase modulation in an optical signal passing through the fiber.1–4 Besides phase shifter and modulator applications, piezoelectric coated optical fibers can also be exploited in electric field sensing devices.5–7 Polymer1–4,8,9 and ZnO10–12 piezoelectric coatings on optical fibers have been investigated for phase modulation applications. Sputter deposited axially symmetric ZnO coatings provide several advantages for piezoelectric fiber optic modulator (PFOM) fabrication and operation in comparison with polymer coatings.13–15 Since the optical fiber is used as the substrate for the deposition of ZnO, the centering problem associated with the fabrication of polymer coatings is eliminated. Thin coatings (on the order of 1 mm) of ZnO may reduce the driving voltage requ
Data Loading...
