Fourier modal method for inverse design of metasurface-enhanced micro-LEDs

We present a simulation capability for micro-scale light-emitting diodes (uLEDs) that achieves comparable accuracy to CPU-based finite-difference time-domain simulation but is more than 10^7 times faster. Our approach is based on the Fourier modal method (FMM) -- which, as we demonstrate, is well suited to modeling thousands of incoherent sources -- with extensions that allow rapid convergence for uLED structures that are challenging to model with standard approaches. The speed of our method makes the inverse design of uLEDs tractable, which we demonstrate by designing a metasurface-enhanced uLED that doubles the light extraction efficiency of an unoptimized device.Comment: 15 pages, 10 figure

High-Efficiency Topology Optimization for Very Large-Scale Integrated-Photonics Inverse Design

This work establishes the mathematical and algorithmic framework necessary for a large-scale, photonics inverse-design methodology that is fully compatible with (and experimentally validated on) commercial, semiconductor-foundry platforms. Specifically, this new methodology quickly and efficiently designs high-performing, multi-functional devices and systems that operate despite various sources of fabrication or operating variability. By overcoming typical tradeoffs between design dimensionality, device footprint, functional complexity, computational cost, and realizable performance, this work paves a practical and proven path toward very large-scale integrated photonics (VLSIP), a key step in designing interferometrically stable architectures within fields like quantum computing, machine learning, and even augmented reality. First, this work introduces the field of photonic inverse design within the context of high-yield photonic integration, highlighting fundamental challenges that continue to impede long-term scalability. The algorithmic framework for a high-efficiency, hybrid time-/frequency-domain adjoint solver, along with comprehensive manufacturing constraints, are then presented. The practicality of this new framework is tested by designing numerous compact, broadband, and robust devices, such as polarization splitters and rotators, full-aperture grating couplers, and 90-degree optical hybrids, all of which were fabricated and tested on different commercial foundry platforms. Finally, these individual devices were monolithically integrated to form a Stokes-Vector Receiver (SVR), a high-capacity direct-detect communications system amenable to long-haul signal processing algorithms. The ultra-compact SVR demonstrates reliable performance across the entire C-band, validating the notion that this new photonics design paradigm is not only compatible with large-scale commercial foundries, but yields high-performing systems robust to common forms of fabrication and environmental variability.Ph.D

High-performance hybrid time/frequency-domain topology optimization for large-scale photonics inverse design

We present a photonics topology optimization (TO) package capable of addressing a wide range of practical photonics design problems, incorporating robustness and manufacturing constraints, which can scale to large devices and massive parallelism. We employ a hybrid algorithm that builds on a mature time-domain (FDTD) package Meep to simultaneously solve multiple frequency-domain TO problems over a broad bandwidth. This time/frequency-domain approach is enhanced by new filter-design sources for the gradient calculation and new material-interpolation methods for optimizing dispersive media, as well as by multiple forms of computational parallelism. The package is available as free/open-source software with extensive tutorials and multi-platform support.Department of Defense (DoD)Simons Foundation, Georgia Electronic Design Center at the Georgia Institute of Technolog

Inverse-Designed Lithium Niobate Nanophotonics

National Natural Science Foundation of China, Research Grants Council, University Grants Committee (City Univ. Hong Kong), Croucher Foundation, Simons Foundatio

Fabrication Tolerant Multi-Layer Integrated Photonic Topology Optimization

Optimal multi-layer device design requires consideration of fabrication uncertainties associated with inter-layer alignment and conformal layering. We present layer-restricted topology optimization (TO), a novel technique which mitigates the effects of unwanted conformal layering for multi-layer structures and enables TO in multi-etch material platforms. We explore several approaches to achieve this result compatible with density-based TO projection techniques and geometric constraints. Then, we present a robust TO formulation to design devices resilient to inter-layer misalignment. The novel constraint and robust formulation are demonstrated in 2D grating couplers and a 3D polarization rotator