Fig. 1. (Color online) (a) Schematic of the hybrid laser with the superimposed optical mode. (b) SEM of cross-section of the hybrid laser^{[21, 22]}.

Fig. 2. (Color online) Schematic of mode conversion tapers for coupling light into the silicon waveguide. The silicon waveguide is in gray while different sections of the top III –V layer with different taper lengths are shown in other colors^[22].

Fig. 3. (Color online) (a, b) Schematic Illustration of micro-transfer printing of III–V gain material on silicon wafers^[19]. (c) Schematic integration and (d) SEM image of the III–V coupon with a silicon photonic waveguide. Top view microscope images of (e) large scale transfer printed coupons on a silicon photonic circuit, and (f) a semiconductor optical amplifier (SOA)^[15].

Fig. 4. (Color online) Schematic representation of the two supermodes, designated by E_o and E_e in the (left) lasing section (middle) coupling section and (right) passive waveguiding section^[11].

Fig. 5. (Color online) Schematic (a) top view and (b) side view of the III–V light emitting heterostructure with Fe:InP cladding in the buried heterostructure configuration integrated on a SOI wafer with an intermediate polysilicon layer (in green). A dual taper configuration is shown in the adiabatic mode transformation region where the laser ridge as well as the underlying polysilicon layers are tapered. The mode evolution of the fundamental TE mode from the gain region to the underlying silicon-poly-Si waveguide is shown in (A)–(H) with the corresponding cross-sections demarcated in (b).

Fig. 6. (Color online) Coupling efficiency vs taper length as function of bottom cladding thickness for (a) air clad ridge laser and (b) buried heterostructure laser and (c) as a function of buried ridge width.

Fig. 7. (Color online) (a) Schematic cross-section of the hybrid laser/light emitter bonded to polysilicon (in green) on device silicon (in purple). Coupling efficiency versus taper length for coupling from (b) poly-Si to 220 nm silicon, and (c) from 220 nm silicon to 400 nm silicon nitride for various oxide gaps between silicon and silicon nitride as indicated in (a).

Fig. 8. (Color online) Reflectivity spectra of DBR reflectors for gratings with (a) etch depth of 100nm and 3600 periods with period Λ = 207 nm, (b) etch depth of 30nm and 7200 periods with Λ = 207 nm. (c) Vernier coupled ring spectra showing thermo-optic tuning around λ = 1295 nm.

Fig. 9. (Color online) Schematic of hybrid TFLN integrated with silicon PICs with (a) embedded electrodes^[26] and (b) un-embedded electrodes. Legend: (yellow) electrodes/metal contacts; (green) silicon or silicon nitride waveguides; (blue) silicon dioxide; (purple) thin film lithium niobate; (red) bonding interface with silicon dioxide between lithium niobate and top of silicon/silicon nitride waveguide.

Fig. 10. (Color online) Steps in the hybrid integration of TFLN on silicon or silicon nitride PICs.

Fig. 11. (Color online) Steps in the hybrid integration of a III–V laser with silicon in a hybrid TFLN on silicon or silicon nitride PIC.

Fig. 12. (Color online) (a) Refractive index profile and (b) optical mode profile of the fundamental TE mode in a thin film ~400 nm LN bonded to a silicon waveguide 240 × 220 nm² separated by 100 nm SiO₂ interface. The top cladding is air.

Fig. 13. (Color online) Tables indicating optical propagation loss contribution from the overlap of the propagating optical mode with the ground and signal electrodes as a function of interface oxide thickness (vertical axis) and spacing between ground and signal electrode (horizontal axis) for hybrid traveling wave modulator configuration with (a) an embedded electrode and (b) an un-embedded electrode.

Fig. 14. (Color online) (a) Cross-section schematic of etched LN integrated with silicon PIC. (b) Optical propagation loss contribution from the overlap of the propagating optical mode with the ground and signal electrodes as a function of interface oxide thickness (vertical axis) and spacing between ground and signal electrode (horizontal axis) for hybrid traveling wave modulator configuration.

Fig. 15. (Color online) Evolution of the optical mode as it couples from the silicon to the etched TFLN in Fig. 14(a) in (a) initially in silicon (b) adiabatic coupling section and (c) mode primarily in the TFLN in the modulator section. (d) Coupling efficiency as a function of adiabatic taper length for different thicknesses of the interface oxide.

Fig. 16. (Color online) (a) Schematic cross-section assuming the TFLN slab has a misalignment offset of 500 nm perpendicular to the waveguide, when bonding. Mode profiles in the (b) adiabatic coupling section and (c) TFLN in the modulator section. (d) Coupling efficiency as a function of adiabatic taper length when waveguides are misaligned.