ANALYSIS OF DOPED LAYER STEP WAVE-GUIDES USING DARK MODES

Results are presented for the analysis of index profiles in step-like waveguide layers formed by proton exchange in LiNbO3 and epitaxially grown Ge-doped quartz. Modeling of the profile with real modes is difficult unless many modes propagate. However, an analysis which includes the substrate modes recorded in dark mode measurements greatly increases the data and hence the confidence in the model of the index profile. The present analysis using a reflectivity function provides the required precision. The data demonstrate that the epitaxial Ge02-doped layer has an index variation with depth. © 1990 IEEE