Wavelength-selective coupling among three vertically integrated optical waveguides by grating couplers

Selective coupling between two specified optical waveguides in a multistory device via radiation modes was proposed and discussed. Three single-TE-mode waveguides consisting of a Corning 7059 glass guiding core layer and a SiO/sub 2/ waveguide-separation layer were stacked on a Si substrate with grating couplers. The coupling length was 0.5 mm. Contradirectional couplings from the first story to the second story at a wavelength of 814 nm and from the first story to the third story at 819 nm with sharp wavelength dependence of 0.5-nm full-width at half-maximum (FWHM) were experimentally demonstrated.