A new method, called barrier coupling, for coupling light into ion-implanted waveguides is presented in analogy to prism coupling. Light is coupled by frustrated total reflection at the barrier region of decreased refractive index by proper variation of the incident angle. Effective indices of guided modes are determined by the minima of the non-incoupled reflected light. The method is used for the determination of the effective indices of an ion-implanted waveguide in . It is simpler than most other techniques, more accurate, and nondestructive.
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