Charge Controlled Ion Exchange - A Way To Reproducible Fabrication Of Integrated Optical Components 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. This process provides some advantages compared to thermal exchange. Exchange time is reduced remarkably, the waveguides can be buried and the index profile can be formed to a nearly circular cross section. A reproducible fabrication of optical waveguides 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. It takes only several seconds to fabricate single mode waveguides in glasses like B-270 (Desalt) and BK-7 (Schott) at a temperature of 693 K and an applied field of 50 V/mm. Directional couplers are extremely sensitive to parameter deviations. They are used to control the reproducibility of the process. The measured variations of the coupling ratio were below 10 percent.