DIRECT MEASUREMENT OF SUBSTRATE REFRACTIVE-INDEXES AND DETERMINATION OF LAYER INDEXES IN SLAB-GUIDING STRUCTURES

We present a new method for accurate and nondestructive measurement of the refractive indices of substrates and guiding layers in slab waveg uides. This method is based on the excitation of leaky waves in substr ates and guided waves in guiding layers owing to the etching of gratin g couplers on the top of structures. It is particularly applicable to high refractive-index materials and to in situ measurements near the e nergy band gap of semiconductor waveguides. We present results that we re obtained for an InP substrate with an InGaAsP epitaxial layer with regard to their refractive indices and temperature coefficients. (C) 1 997 Optical Society of America.