Adjoint optimization of polarization-splitting grating couplers

Area of Science:

• Optoelectronics
• Nanophotonics
• Integrated Optics

Background:

• Polarization-splitting grating couplers (PSGCs) are essential components in integrated photonic circuits for separating light based on polarization.
• Existing PSGC designs often require complex structures or additional components like bottom reflectors, impacting performance and fabrication.
• Efficient and compact PSGCs are crucial for advancing photonic integrated circuits for applications like optical communication and sensing.

Purpose of the Study:

• To design and simulate a high-performance polarization-splitting grating coupler (PSGC) in silicon-on-insulator (SOI).
• To achieve the best simulated performance for PSGCs without a bottom reflector.
• To leverage advanced optimization techniques for exploring novel device geometries.

Main Methods:

• Design of a PSGC using silicon-on-insulator (SOI) material.
• Utilization of adjoint method-based shape optimization to explore complex device geometries.
• Numerical simulations to evaluate the performance of the designed PSGC.

Main Results:

• Achieved a peak loss of 1.2 dB in numerical simulations for the PSGC.
• Demonstrated the best simulated performance for PSGCs without a bottom reflector to date.
• Extracted physics-based, process-independent knowledge from the adjoint optimization process.

Conclusions:

• The developed PSGC design offers state-of-the-art simulated performance.
• Adjoint optimization is a powerful tool for designing complex photonic devices.
• The extracted design principles can be readily transferred to other photonic platforms.