Side edge emission from a waveguide substrate

In this study, we fabricated embedded titanium dioxide (TiO₂) nanograting structures with slanted cross section on a silicon dioxide (SiO₂) substrate using electron beam lithography (EBL) and reactive ion etching (RIE) methods, and we analyzed their optical signals. The surface morphologies of the embedded TiO₂ nanograting structures were monitored by a scanning optical microscope (SEM). By focusing the transverse electric (TE) polarized beam with the wavelength λ=633nm at the incident angle θ=22.0^∘ from the rear side of TiO₂ face, we could observe +1st and -2nd diffraction orders with diffraction efficiencies (I/I): I₁=23% and I₂=19%, respectively, on a SiO₂/TiO₂ interface. Diffraction beams were waveguided to both left and right directions in a SiO₂ substrate via total internal reflection (TIR); next, two guided beams were emitted from the side edges of the substrate. This work is expected to develop a highly efficient two-way waveguide optical interconnector.