Simulation for paper

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

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

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

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!

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

Structure 50μm 30μm 14o

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

Simulation Result Waveguide monitor Almost zero reflection from grating

Simulation Result Fiber monitor Peak transmission 0.393(non-uniform), 0.365 (uniform) 0.32dB increase

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