Surface Reflectivity of Graded-Index Layers Formed by Ion Exchange in Glass

概要

論文の詳細を見る
In this paper, we theoretically analyze the reflectivity of a graded-index layer made by ton exchange in glass. We use two approaches, i.e., the matrix and the wave equation. The results of both approaches are in good agreement when refractive index profiles are approximated by a sufficient number of discrete layers. Calculated results show that when the effective thickness of an ion-exchanged layer is larger than the wavelength of incident light, the reflectivity is mainly determined by the refractive index at the surface, and the internal refractive index has little influence on the reflectivity. In other words, the measurable effective thickness from the surface reflectivity is below the wavelength of incident light. This thickness, however, is generally below the cutoff thickness, i.e., the minimum thickness enables graded-index layers to be used as optical waveguides. This indicates the difficulty of a nondestructive measurement of the refractive index profile of ion-exchanged capital waveguides based on their surface reflectivity. On the other hand, our results show that surface reflectivity can assist the inverse Wentzel-Kramers-Brillouin (WKB) method to accurately determine the refractive index at the surface of a gradient optical waveguide.
社団法人応用物理学会の論文
1999-06-15