Optimization and Experiments of On-Chip Silicon Nitride Grating Couplers

Fig. 2. Effect of various parameters on coupling efficiency and electric field distribution of grating coupler. (a) Coupling efficiency varying with angle of incidence; (b) coupling efficiency varying with fill factor; (c) coupling efficiency varying with grating etching depth, grating height, and grating constant; (d) electric field profiles of 2D grating coupler

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Fig. 3. Schematic diagram of 3D direct waveguide grating coupler

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Fig. 4. xz and xy surface electric field profiles of grating coupler. (a)(b) 3D direct waveguide grating coupler; (c)(d) 3D half etched and focused waveguide grating coupler; (e)(f) 3D fully etched and focused waveguide grating coupler

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Fig. 5. Production process of Si₃N₄ waveguide

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Fig. 6. SEM images of 3D fully etched and focused waveguide grating coupler. (a) Overall view; (b) etching structure

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Fig. 7. Test system diagram of grating coupler

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Fig. 8. Plot of waveguide loss varying with waveguide length

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Fig. 9. Test result of spectral bandwidth of grating coupler

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Table 1. Structural optimization parameters of 3D waveguide grating couplers

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Table 1. Structural optimization parameters of 3D waveguide grating couplers

Type of 3D grating coupler

Angle of incidence

$θ$ /（°）

Height of grating coupler

H /nm

Etching depth

h /nm

Grating constant

Λ

/nm

Fill

factor

F_f

Width of waveguide

w /nm

Angle of grating coupler

$θ$ /（°）

3D direct type

6.05

256

152

478

0.40

1000

3D half etched and focused type

6.78

256

163

480

0.43

500

3D fully etched and focused type

10.96

303

533

0.71

500

Table 2. Structural optimization parameters of 3D fully etched and focused waveguide grating coupler
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Table 2. Structural optimization parameters of 3D fully etched and focused waveguide grating coupler
Angle of grating coupler
$θ$ /（°）
Etch depth
h /nm
Grating constant $Λ$ /nm
Fill factor
F_f
Width of waveguide
w /nm
22 300 670 0.78 150

Table 3. Test results of coupling efficiency of fully etched and focused coupling grating at 785 nm
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Table 3. Test results of coupling efficiency of fully etched and focused coupling grating at 785 nm
Test
Incident optical power
P_in /mW
Emergent light power
P_out /μW
Coupling efficiency
η /%
1 1.5 32.80 19.80
2 1.5 32.64 19.75
3 1.5 33.12 19.89
4 1.5 33.76 20.08
5 1.5 33.60 20.04

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Na Ran, Xinyang Chen, Zhengkun Wang, Jie Zhang. Optimization and Experiments of On-Chip Silicon Nitride Grating Couplers[J]. Acta Optica Sinica, 2023, 43(1): 0113002

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Paper Information

Category: Integrated Optics

Received: Jun. 13, 2022

Accepted: Jul. 11, 2022

Published Online: Jan. 6, 2023

The Author Email: Zhang Jie (zhangjie@cqu.edu.cn)

DOI:10.3788/AOS221307

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Structural optimization parameters of 3D waveguide grating couplers

Table 1. Structural optimization parameters of 3D waveguide grating couplers

Table 2. Structural optimization parameters of 3D fully etched and focused waveguide grating coupler

Table 2. Structural optimization parameters of 3D fully etched and focused waveguide grating coupler

Table 3. Test results of coupling efficiency of fully etched and focused coupling grating at 785 nm

Table 3. Test results of coupling efficiency of fully etched and focused coupling grating at 785 nm