Valerio Vitali, Thalía Domínguez Bucio, Cosimo Lacava, Riccardo Marchetti, Lorenzo Mastronardi, Teerapat Rutirawut, Glenn Churchill, Joaquín Faneca, James C. Gates, Frederic Gardes, Periklis Petropoulos, "High-efficiency reflector-less dual-level silicon photonic grating coupler," Photonics Res. 11, 1275 (2023)

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- Photonics Research
- Vol. 11, Issue 7, 1275 (2023)

Fig. 1. (a) 2D schematic view and simulation layout of the proposed dual-level Si GC; (b) cross-sectional schematic with the parameter names used to indicate the GC dimensions.

Fig. 2. (a) 2D numerical simulations of the CE at 1550 nm as a function of the bottom linear apodization factor R bot and the etching depth e considering a single-level GC with a waveguide thickness h bot = 220 nm . Other parameters used in the simulations are B = 2 μm , F in , bot = 0.9 , θ = 14.5 ° , and T = 720 nm . (b) 3D numerical simulations of the CE as a function of wavelength for the best-performing single-level and dual-level GC considering h bot = 220 nm .

Fig. 3. 2D numerical simulations of (a) directionality and (b) CE at 1550 nm as a function of the top linear apodization factor R top and thickness of the top level h top for a dual-level GC with h bot = 220 nm . Other parameters used in the simulations are e = 110 nm , R bot = 0.0275 μm − 1 , B = 2 μm , F in , bot = 0.9 , F in , top = 0.1 , θ = 14.5 ° , and T = 720 nm .

Fig. 4. Fabrication process diagram for the dual-level GC: (a) starting from SOI wafer with a Si thickness of 340 nm; (b) bottom GC level etching; (c) top GC level etching; (d) waveguide etching; (e) SiO 2 cladding deposition. (f) Top-view and (g) angled-view SEM images of a fabricated device.

Fig. 5. Simulated (red curve) and experimentally measured (blue curve) CE as a function of wavelength for the fabricated dual-level GC with a bottom waveguide thickness h bot = 220 nm and top-level thickness h top = 120 nm .

Fig. 6. (a) Peak CE (CE peak , left y axis) and peak wavelength (λ peak , right y axis) as a function of the mask misalignment; variation of the dimensions of the first top tooth and first bottom trench in the cases of (b) aligned masks, (c) − 30 nm mask misalignment, and (d) + 30 nm mask misalignment.
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Table 1. Summary of the Best Numerically Simulated (CES) and Experimentally Measured (CEE) Coupling Efficiencies Reported in the Literature for Different GCs in the C-Telecom Banda
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Table 2. Optimal Dimensions (Common Period Λ , Bottom Tooth Width L o,bot, and Top Tooth Width L o,top) Obtained from the Optimization of the Apodized Dual-Level Si GC with Waveguide Thickness h bot = 220 nm and Top Level Thickness h top = 120 nma

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