In optical planar and/or channel waveuides, determination of two parameters such as: the depth and the waveguide index with the use of the rn-line spectroscopy (prism coupling method) involves measuring of at least two coupling angles of the guiding modes. Most of integrated optical devices operate in sigle-mode regime but such devices developed for 2-nd and 3-rd transmission windows are multimodal within the VIS range thus the conventional rn-line study with the use of the He-Ne laser yields in evaluation of the waveguide parameters under examination. However, the conventional m-line procedure of the determination of the waveuide parameters fails for single-mode structures developed for the application within the VIS-range. A method presented in the paper involves an additional two-beam interferometric examination of the slab with a waveguiding structure. The interference of the beams reflected from the upper and lower surfaces of the slab results in a fringe pattern. Within the region of the waveguide boundary one observes the fringe shift related to the difference of optical paths of the beams in- and outside of the waveguide. The microscopic study of that fringe pattern results in an additional relation of the waveguide depth and its index. A substitution of the waveguide depth by the last relation results in a modified modal eqaution for the waveguide index that can be solved by conventional numerical methods.

Date Published: 24 September 1993
PDF: 4 pages
Proc. SPIE 1711, High-Performance Optical Spectrometry, (24 September 1993); doi: 10.1117/12.155672

Published in SPIE Proceedings Vol. 1711:
High-Performance Optical Spectrometry
Maksymilian Pluta; Aleksandra Kopystynska; Mariusz Szyjer, Editor(s)