Simple method of measuring propagation properties of integrated optical waveguides: an improvement

In this paper we report a simple method of measuring mode propagation losses of integrated optical waveguides with small scattering. The basic technique, reported previously, uses a microcomputer-assisted video camera; here we have improved our observation scheme by coating the optical waveguide with a thin film of fluorescent dye (Nile Blue A perchlorate) thus permitting observation of the optical fields. The Nile Blue A perchlorate absorbs light centered at 0.63 microm and emits light centered at 0.69 microm. We have measured a mode propagation loss of the order of 0.1 dB/cm of a potassium ion-exchanged glass waveguide and confirmed the damped oscillatory behavior of the attenuation vs a slightly lossy thin-film thickness curve for the ion-exchanged waveguide coating with an indium tin oxide film.