Fig. 8: Examples of waveguide-to-waveguide couplers utilizing edge coupling.
From: Advances in waveguide to waveguide couplers for 3D integrated photonic packaging
In (a) and (b), schematic and experimental images, respectively, of an inverse taper edge coupler from a SiN waveguide to an InP DFB laser passively assembled using pick-and-place tools (reprinted with permission from ref. 75 ©2023 IEEE). In (c), a side view of InP to SOI coupling is shown, where the red rectangle is the InP die and the gray etched shape is the SOI die. The black line across the InP and SOI is meant to show the waveguides on both surfaces being coupled. An experimental microscope image of the side view is shown on the bottom, demonstrating the submicron 3D alignment using mechanical stops (reprinted from ref. 372, ©2018 T. Barwicz et al. with permission from Elsevier and licensed under CC BY-NC-ND 4.0). In (d), a hybrid DBR laser based on flip-chip GaSb amplifiers and SOI waveguides is shown48 (©2022 N. Zia et al., licensed under CC BY 4.0). In (e), coupling between polymer waveguide layers using MMI devices92 (©2024 M. Weigel et al., licensed under CC BY 4.0). In (f, g), SOI to SOI or SiNx to SiNx flip-chip coupling using integrated GRIN lenses322 (©2025 D. Weninger et al., licensed under CC BY 4.0)
