Implementing commercial inverse design tools for compact, phase-encoded, plasmonic digital logic devices

TL;DR

This paper demonstrates the implementation of commercial inverse design tools for complex plasmonic photonic devices, comparing their performance to conventional designs and discussing current limitations and future improvements.

Contribution

It showcases the application of inverse design tools to complex plasmonic devices, highlighting their capabilities and limitations in practical device development.

Findings

Inverse-designed devices perform comparably to conventional ones.

Limitations in inverse design tools affect device complexity and encoding density.

Discussion on potential improvements for inverse design methodologies.

Abstract

Numerical simulations have become an essential design tool in the field of photonics, especially for nanophotonics. In particular, 3D finite-difference-time-domain (FDTD) simulations are popular for their powerful design capabilities. Increasingly, researchers are developing or using inverse design tools to improve device footprints and performance. These tools often make use of 3D FDTD simulations and the adjoint optimization method. In this work, we implement a commercial inverse design tool with these features for several plasmonic devices that push the boundaries of the tool. We design a logic gate with complex design requirements, as well as a y-splitter and waveguide crossing. With minimal code changes, we implement a design that incorporates phase encoded inputs in a dielectric-loaded surface plasmon polariton waveguide. The complexity of the requirements in conjunction with limitations in the inverse design tool force us to make concessions regarding the density of encoding and to use on-off keying to encode the outputs. We compare the performance of the inverse-designed devices to conventionally-designed devices with the same operational behavior. Finally, we discuss the limitations of the inverse design tools for realizing complex device designs and comment on what is possible at present and where improvements can be made.