[OPTICAL REVIEW Vol. 3, No. 2 (1996) 114-119]

Fabrication of Spot Size Converters for Optical Chemical Sensors by Distributed-Field-Assisted Ion-Exchange

De-Kui QING,*[footnote] Kiminori ITOH and Masayuki MURABAYASHI

Institute of Environmental Science and Technology, Yokohama National University, Tokiwadai, 156, Hodogaya-ku, Yokohama, 240 Japan

(Received November 27, 1995; Accepted January 16, 1996)

We propose a new method for fabricating optical waveguides with nonuniform thickness by controlling the electrical field distribution during the field-assisted ion-exchange. We refer to this method as distributed-field-assisted ion-exchange. The distribution of the intensity of the electrical field was simulated for different electrode configurations, and was compared with experimental diffusion depth distribution of K+-Na+ exchange in sodalime slide glass. A unique bath was designed for the distributed-field-assisted ion-exchange. Using a three-electrode configuration, we obtained, for instance, a 2 cm-long spot size converter with thickness changes of from 12 μm to 2 μm. This technique can be used to fabricate waveguides for optical chemical sensors.

Key words : fabrication, optical waveguide, spot size converter, optical chemical sensor, distributed-field-assisted ion-exchange

*On leave from State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Beijing, China 100080.