Author Affiliations
1Centre for Photonic Systems, Electrical Engineering Division, Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK2Department of Information Technology (INTEC), Photonics Research Group, Ghent University-imec, 9052 Ghent, Belgiumshow less
Fig. 1. (a) Schematic of the cross section of a III-V-on-silicon vertically coupled waveguide system. (b)–(d) Calculated maps of γ for different width combinations of the III-V and Si waveguide when the misalignment is 0, 0.5, and 1.0 μm, respectively. The dashed white lines and the orange dots represent the width combinations for, respectively, the linearly tapered structure and the multisegmented tapered structure.
Fig. 2. (a) 3D schematic diagram of the proposed III-V-on-silicon vertical coupler. (b) and (c) Top view of the vertical couplers with, respectively, a linear taper structure and a multisegmented taper structure.
Fig. 3. Simulated coupling efficiency versus the length L of the linear taper vertical couplers with different lateral misalignments. The theoretical calculation for a perfectly phase-matched conventional resonant coupler when Δm is 1.0 μm is also presented for reference.
Fig. 4. (a) Waveguide widths of the vertical coupler with multisegmented taper structure along the propagation direction z. (b) Simulated coupling efficiency versus the lateral misalignment. (c) Normalized power of the two supermodes (even and odd) along the propagation direction when Δm is 1.0 μm. Insets show their simulated transverse electric field profiles at z=57 μm. (d) Simulated electric field profiles at the input cross section and the output cross section when Δm is, respectively, 0, 0.5, and 1.0 μm.
Fig. 5. (a) Simulated map of the coupling efficiency with different width variations of the III-V and Si waveguide when the coupler is 1.0 μm misaligned. (b) Simulated coupling efficiency versus the thickness of the BCB bonding layer with different misalignments. (c) Simulated coupling efficiency versus wavelength with different misalignments.
Fig. 6. (a) Cross section schematic of a heterogenous coupled waveguide system based on 220 nm SOI platform with poly-Si overlay. (b) Waveguide widths of the multisegmented vertical coupler along the propagation direction. (c) FDTD simulated coupling efficiency versus the lateral misalignment.
Fig. 7. Simulated coupling efficiency of the optimized couplers with different numbers of taper segments when Δm is ±1.0 μm. Inset shows the coupling efficiency of a three-segmented coupler versus the lateral misalignment.
References | Principle | Materials | Length | Efficiency | Alignment Tolerance | Tolerance of Width Variation () | Bandwidth |
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[23] | Adiabatic | AlGaInAs/Si | 210 μm | 98% | () | N.A. | N.A. | [43] | Adiabatic | InGaAsP/a-Si:H | 224 μm | 93% | () | N.A. | N.A. | [39] | Adiabatic | InGaAsP/InP | 180 μm | 83% | N.A. | | N.A. | [40] | Adiabatic | InGaAsP/InP | 293 μm | 90% | N.A. | | N.A. | [34] | Resonant | AlGaInAs/Si | 8 μm | 95% | () | N.A. | 1.5–1.6 μm () | [35] | Resonant | AlGaInAs/Si | 5 μm | 98% | N.A. | N.A. | 1.5–1.6 μm () | [32] | Resonant | InGaAsP/InP | 24 μm | 97% | N.A. | | N.A. | [44] | Resonant | AlGaInAs/InP | 55 μm | 96% | () | | 1.23–1.4 μm () | This work | Hybrid | AlGaInAs/Si | 87 μm | 98% | () | | 1.44–1.74 μm () |
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Table 1. Comparison of Several Different Vertical Couplersa
Performance Metrics | Adiabatic Coupler | Multisegmented Tapered Coupler |
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Device length | 237 μm | 87 μm | Alignment tolerance | 1.0 μm () | 1.0 μm () | Tolerance of width variation | () | () | Tolerance of BCB thickness variation | () | () | Bandwidth | 1.49–1.58 μm () | 1.44–1.74 μm () |
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Table 2. Comparison to an Adiabatic Coupler