Analytical level set fabrication constraints for inverse design.

Area of Science:

• Nanophotonics
• Computational electromagnetics
• Optical engineering

Background:

• Inverse design methods enable arbitrary nanophotonic device geometries with high efficiency and novel functionalities.
• Ensuring the fabricability of these unrestricted geometries during optimization is a significant challenge.

Purpose of the Study:

• To develop a fabrication-aware inverse design method for nanophotonic devices.
• To incorporate geometric constraints directly into the optimization process.

Main Methods:

• Constructed a fabrication constraint penalty function for level set geometry representations.
• The penalty function limits device gap size and boundary curvature.
• Integrated this penalty into an automated optical design flow using quasi-Newton optimization.

Main Results:

• Successfully designed waveguide demultiplexers (WDM) and mode converters with varying footprints and minimum feature sizes.
• Demonstrated experimental characterization of three WDMs with feature sizes of 80 nm, 120 nm, and 160 nm.

Conclusions:

• The developed method effectively integrates fabrication constraints into inverse design for nanophotonics.
• This approach facilitates the creation of complex, manufacturable nanophotonic devices.