1. Simulation for paper

2. Grating coupler Device to couple light between chip and fiber
Efficient for chip testing

3. Why simulate grating coupler
Most of devices need couplers for using or testing
Loss of couplers is important factor

4. Principle Limiting of grating coupler efficiency neff: Effective index
Coupled light to bottom substrate
Mode mismatch between grating and fiber
neff: Effective index
nc: Effective index of cladding
Λ: Pitch
F: Fill factor
FΛ: Trench

5. Simulation Target IME IMEC IHP LETI Etch depth 60nm 50nm 70nm
Insertion Loss
3.1dB
2dB
4.5dB
Characteristic
Non-uniform grating
poly-si layer for grating
Specification of grating couplers
Trench of non-uniform grating
Reduce mode mismatch between grating and fiber
0.36dB loss reduced!

6. Simulation Method 3D FDTD simulation Need long time to simulate
Hard to simulate large , complex devices

7. Structure
50μm
30μm
14o

8. Simulation Setup Waveguide mode source used for optical source
Mode of Mode source
And waveguide monitor
Mode of fiber monitor
Waveguide mode source used for optical source
Expansion monitor used for detect signal

9. Simulation Result Waveguide monitor
Almost zero reflection from grating

10. Simulation Result Fiber monitor Peak transmission
0.393(non-uniform), (uniform)
0.32dB increase

11. Conclusion Grating coupler simulation have many advantages and useful
Grating couplers are challenging to simulate
Large scale
Complex analysis
Performance development by simulation is possible