Inverse design of compact multimode cavity couplers

Area of Science:

• Silicon photonics
• Integrated optics
• Nanophotonics

Background:

• Efficient light coupling between on-chip optical sources and cavities is crucial for silicon photonics.
• Existing design tools struggle to simultaneously manage multi-mode coupling in compact resonators and single waveguides.

Purpose of the Study:

• To develop a systematic design tool for creating wavelength-scale waveguide-cavity couplers.
• To enable simultaneous control of coupling across multiple modes and wavelengths in silicon photonic devices.

Main Methods:

• A large-scale adjoint optimization approach was employed.
• Numerical simulations were used to demonstrate the effectiveness of the developed method.

Main Results:

• The adjoint optimization successfully designed novel waveguide-cavity couplers.
• Demonstrated critical or near-critical coupling between multi-ring cavities and a single waveguide.
• Achieved coupling at up to six widely separated wavelengths (560-1500 nm).

Conclusions:

• The proposed adjoint optimization method provides a powerful tool for designing advanced silicon photonic couplers.
• The discovered couplers are suitable for broadband, multi-wavelength on-chip nonlinear optical devices.