Miao Tian, Minni Qu, Liying Wu, Xiulan Cheng. Progress on Asymmetrical Grating Couplers for Vertical Coupling[J]. Laser & Optoelectronics Progress, 2021, 58(5): 0500004
- Laser & Optoelectronics Progress
- Vol. 58, Issue 5, 0500004 (2021)
![Structural diagram of grating coupler [15]. (a) In-coupling; (b) out-coupling](/richHtml/lop/2021/58/5/0500004/img_1.jpg)
Fig. 1. Structural diagram of grating coupler [15]. (a) In-coupling; (b) out-coupling
![Typical grating couplers[18]. (a) Whole structural diagram; (b) cross sectional diagram](/richHtml/lop/2021/58/5/0500004/img_2.jpg)
Fig. 2. Typical grating couplers[18]. (a) Whole structural diagram; (b) cross sectional diagram
Fig. 3. In-coupling based on asymmetrical grating
Fig. 4. Simulation of slanted grating and conventional rectangular grating [20]
Fig. 5. Realization of tilted etching using Faraday cage to change plasma direction in RIE[21].（a）Structural diagram; (b) SEM image of obtained slanted grating
Fig. 6. Cross-section of SiO2 slanted grating [22]
Fig. 7. SEM image of slanted grating etched with tilted RIE [15]
Fig. 8. Design and fabrication of slanted grating coupler. (a) Incident slanted grating coupler [23]; (b) SEM image of slanted grating coupler in SOI waveguide layer based on FIB [26]
Fig. 9. Angle relationship of blazed grating[27]
Fig. 10. SEM image of blazed grating [34]
Fig. 11. PMMA template grating [36] .FIB cross-sectional SEM images (a) before and (b) after imprinting; (c) imprinted grating in OrmoCore
Fig. 12. Design principle of binary blazed grating[35]. (a) Blazed grating; (b) equivalent gradient refractive index grating; (c) binary blazed grating
Fig. 13. Shadowing effect of blazed grating[39]
Fig. 14. Structural diagram of binary blazed grating. (a) 2D structure[43]; (b) 3D structure[43]; (c) coupling schematic of binary blazed gratings[47]; (d) SEM image of binary blazed grating coupler[48]
Fig. 15. Several less popular asymmetrical gratings. (a) Schematic of tilted rectangular grating coupler[50] ; (b) double-depth double-groove grating coupler[51]; (c) angle evaporation schematic of high-refractive-index material[52]; (d) structure obtained based on Fig. (c) [52]
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Table 1. Feature comparison of common asymmetrical gratings
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