On the accuracy of the measurement of propagation loss in channel waveguides using the Fabry-Perot resonance method

The resonance method of measuring the propagation losses in dielectric channel waveguides is revisited. We experimentally and theoretically demonstrate how the inadequate quality of the waveguide resonator preparation detrimentally affects the results of the measurements. Minute tilts (on the order of 1 degrees) of the anneal-proton-exchanged LiNbO3 waveguide facets result in overestimation of loss factor by several hundreds of percent. Conclusions based on this error may result in rejection of low-loss samples perfectly suitable for resonant waveguide devices and thus constitute a useful warning for the experimentalist involved in measurements of waveguide losses. (C) 2001 Elsevier Science B.V. All rights reserved.