Adjoint-method-inspired grating couplers for CWDM O-band applications

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Semiconductor Device Fabrication

Background:

• Silicon-on-Insulator (SOI) technology is a key platform for integrated photonics.
• Efficient coupling between optical fibers and photonic integrated circuits is crucial for optical communication systems.
• Coarse Wavelength Division Multiplexing (CWDM) O-band (1270-1330 nm) is essential for data transmission.

Purpose of the Study:

• To design and simulate a broadband grating coupler for the CWDM O-band on an SOI platform.
• To achieve sufficient bandwidth and low insertion loss for efficient optical signal coupling.
• To enable compatibility with commercial CMOS fabrication and wafer-level testing.

Main Methods:

• Adjoint method-based geometry optimization for grating design.
• Parameterization for Design of Experiments (DOE) construction.
• Simulation of grating coupler performance, including loss and bandwidth.

Main Results:

• A grating coupler design covering the entire CWDM O-band (1270-1330 nm) was achieved.
• Simulated peak insertion loss of 3.2 dB.
• Simulated 1-dB bandwidth from 1265 nm to 1338 nm, exceeding the target CWDM O-band range.

Conclusions:

• The designed grating coupler offers broadband performance suitable for CWDM O-band applications.
• The design methodology is compatible with commercial CMOS foundries and wafer-level testing.
• This work contributes to the advancement of efficient fiber-to-chip coupling in integrated photonics.