Abstract

Integrable narrow-band wavelength filters are essential elements of several important photonic integrated circuits, including, for example, an amplifier/filter and demultiplexer/detector. Recently we demonstrated that grating-assisted codirectional coupling between dissimilar epitaxially grown slab waveguides provides a means of attaining highly wavelength-selective coupling.¹ Although the demonstration with slab waveguides provides a verification of the principle, for practical application either as a discrete device or for photonic integration, a device based on strip or channel waveguides is clearly essential. Here we report the first demonstration of grating-assisted coupling between two vertically stacked buried-rib strip waveguides. Wavelength-selective couplers with filter bandwidth less than 20 Å have been demonstrated. Furthermore, the photonic-circuit processing technology reported here allows convenient lateral spatial separation of input/output waveguides. More generally, this integration approach allows selective vertical coupling between otherwise noninteracting two-dimensional photonic circuits fabricated on different planar slabs.

© 1991 Optical Society of America