Charge Controlled Reproducible Ion Exchange For Buried Strip Waveguides In Glass

Abstract

Integrated optical components in glass are commonly fabricated by thermal or field assisted ion exchange. We introduce the charge controlled field assisted ion exchange. A reproducible fabrication of optical wave-guides is achieved by using the exchanged charge as the controlling process parameter. The ion current is integrated by a computer controlled unit which stops the process at a preset charge. The charge corresponds to the amount of exchanged ions and a reproducible process is available. Introducing the exchanged charge as the process determining parameter requires a resistant mask material and a special vacuumchuck containing the anode melt and holding the wafer. This is necessary to exclude any leak current during the exchange process. We get resistant masks only when using oxide coatings, which are formed by an anodic oxidation of evaporated aluminium films in a dilute ammonium-tartrat solution [(NH4)2C2H4O6]. It takes only several seconds to fabricate single mode waveguides in glasses such as B-270 (Desag) and BK-7 (Schott) at a temperature of 693 K and an applied electrical field of SO V/mm. Directional couplers are extremely sensitive to parameter deviations . They were used to control the reproducibility of the process. Buried multimode waveguides with a circular cross section have been fabricated by a two step ion exchange in B-270 glass.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.