Fig. 1. Overview of bonding fabrication for 3D PIC on SiPh

Fig. 2. Overview of deposition fabrication for 3D PIC on SiPh

Fig. 3. SEM image of microring resonator on the DLSOI platform^［22］

Fig. 4. Overview of the 3-D heterogeneous integration platform used to construct the single-chip OPA^［23］

Fig. 5. Grating based interlayer transition ^［24］

Fig. 6. Cross section SEM of polysilicon racetrack resonators coupled to crystalline silicon waveguides before oxide cladding. Inset shows the definition of r and coupling length L₀^［27］

Fig. 7. Raman spectra and SEM micrographs of poly-Si waveguide after laser crystallized^［30］

Fig. 8. Schematic of multilayer platform including tapered vertical coupler and waveguides crossing^［36］

Fig. 9. Fabricated multilayer star-coupler and its test results^［36］

Fig. 10. Schematic of the proposed three layer SiN-on-Si platform and its X-TEM images^［37］

Fig. 11. Optical micrograph of a fabricated S&S 4 × 4 switch^［38］

Fig. 12. Circuit diagram，microscopic image and the measured losses of the proposed polarization-diversity PILOSS switch^［39］

Fig. 13. 3D integrated wavelength demultiplexer^［47］

Fig. 14. 2D OPAs based on PolyBoard PICs ^［48］

Fig. 15. 3D six-mode（de）multiplexer^［51］