Topological inverse design of nanophotonic devices with energy constraint

Abstract

In this paper, we introduce an energy constraint to improve topology-based inverse design. Current methods typically place the constraints solely on the device geometry and require many optimization iterations to converge to a manufacturable solution. In our approach the energy constraint directs the optimization process to solutions that best contain the optical field inside the waveguide core medium, leading to more robust designs with relatively larger minimum feature size. To validate our method, we optimize two components: a mode converter (MC) and a wavelength demultiplexer. In the MC, the energy constraint leads to nearly binarized structures without applying independent binarization stage. In the demultiplexer, it also reduces the appearance of small features. Furthermore, the proposed constraint improves the robustness to fabrication imperfections as shown in demultiplexer design. With energy constraint optimization, the corresponding spectrum shifts under ±10 nm dimensional variations are reduced by 17% to 30%. The proposed constraint is unique in simultaneously taking both geometry and electric field into account, opening the door to new ideas and insights to further improve the computationally intensive topology-based optimization process of nanophotonic devices.

Topological Nanophotonic Wavelength Router Based on Topology Optimization

“…The second stage is topology optimization. Topology optimization, as an important kind of optimization method, is at first applied in mechanics [25] and has been broadly used in many areas including nanophotonic design in recent years [26][27][28][29]. The optimization aim of the algorithm is to find the best distribution of two kinds of material, which can fulfill the design target under given conditions.…”

“…The second stage is topology optimization. Topology optimization, as an important kind of optimization method, is at first applied in mechanics [25] and has been broadly used in many areas including nanophotonic design in recent years [26][27][28][29].…”

“…The second stage is topology optimization. Topology optimization, as an important kind of optimization method, is at first applied in mechanics [25] and has been broadly used in many areas including nanophotonic design in recent years [26][27][28][29]. The significance of topology optimization is obvious in our work because it enlarges the parameter space greatly to achieve freeform structure design and can realize high performance under given conditions.…”

On-chip Optical Phase Monitoring in Multi-Transverse-Mode Integrated Silicon-based Optical Processors

“…5 (a), increasing ζ from 1.09 (1.96/1.8) to 1.5 leads to a larger change in the detected TE1 power while sweeping ϕ from 0 to 2π, thus larger ERTE1. A mode sensitive phase shifter with ζ close to 1.5 can be realized using inverse design [34,35], or subwavelength grating (SWG) structures [36] and will highly contribute to an optimized performance of MTMOPs. The mode sensitive phase shifter design may rely on the fact that the TE0 propagates mainly in the multimode waveguide center whereas TE1 field pattern exhibits two lobes closer to the waveguide sidewalls.…”

Efficient method for accelerating line searches using a combined Schur complement domain decomposition and Born series expansions in photonic-based adjoint optimization

“…Optimization approach based on gradient descent has been well established for the inverse design and optimization of both linear and nonlinear photonic devices [1,2,3,4,5,6,7,8]. In each step of the optimization, one starts with a candidate structure and computes the gradient in the design parameter space of its objective function.…”