arXiv subjects

Jesse Lu

Publications and source records attributed to Jesse Lu.

12 recordsLinked to original sources

arXiv2025

Inverse-Designed Silicon Nitride Nanophotonics

Silicon nitride photonics has enabled integration of a variety of components for applications in linear and nonlinear optics, including telecommunications, optical clocks, astrocombs, bio-sensing, and LiDAR. With the advent of inverse design - where desired device performance is specified and closely achieved through iterative, gradient-based optimization - and the increasing availability of silicon nitride photonics via foundries, it is now feasible to expand the photonic design library beyond the limits of traditional approaches and unlock new functionalities. In this work, we present inverse-designed photonics on a silicon nitride platform and demonstrate both the design capabilities and experimental validation of manipulating light in wavelength and spatial mode dimensions to high-Q resonators with controllable wavelength range and dispersion. Furthermore, we use these inverse-designed structures to form optical cavities that hold promise for on-chip nonlinear and quantum optics experiments.

physics.optics↗

arXiv2025

A systolic update scheme to overcome memory bandwidth limitations in GPU-accelerated FDTD simulations

The exponential growth of artificial intelligence has fueled the development of high-bandwidth photonic interconnect fabrics as a critical component of modern AI supercomputers. As the demand for ever-increasing AI compute and connectivity continues to grow, the need for high-throughput photonic simulation engines to accelerate and even revolutionize photonic design and verification workflows will become an increasingly indispensable capability for the integrated photonics industry. Unfortunately, the mainstay and workhorse of photonic simulation algorithms, the finite-difference time-domain (FDTD) method, because it is a memory-intensive but computationally-lightweight algorithm, is fundamentally misaligned with modern computational platforms which are equipped to deal with compute intensive workloads instead. This paper introduces a systolic update scheme for the FDTD method, which circumvents this mismatch by reducing the need for global synchronization while also relegating the need to access global memory to the case of boundary values between neighboring subdomains only. We demonstrate a practical implementation of our scheme as applied to the full three-dimensional FDTD algorithm that achieves a performance of roughly 0.15 trillion cell updates per second (TCUPS) on a single Nvidia H100 GPU. Our work paves the way for the increasingly efficient, cost-effective, and high-throughput photonic simulation engines needed to continue powering the AI era.

physics.optics↗

arXiv2019

Data-driven acceleration of Photonic Simulations

Designing modern photonic devices often involves traversing a large parameter space via an optimization procedure, gradient based or otherwise, and typically results in the designer performing electromagnetic simulations of correlated devices. In this paper, we present an approach to accelerate the Generalized Minimal Residual (GMRES) algorithm for the solution of frequency-domain Maxwell's equations using two machine learning models (principal component analysis and a convolutional neural network) trained on simulations of correlated devices. These data-driven models are trained to predict a subspace within which the solution of the frequency-domain Maxwell's equations lie. This subspace can then be used for augmenting the Krylov subspace generated during the GMRES iterations. By training the proposed models on a dataset of grating wavelength-splitting devices, we show an order of magnitude reduction ($\sim 10 - 50$) in the number of GMRES iterations required for solving frequency-domain Maxwell's equations.

physics.comp-ph↗

arXiv2015

Inverse design and demonstration of a compact and broadband on-chip wavelength demultiplexer

Integrated photonic devices are poised to play a key role in a wide variety of applications, ranging from optical interconnects and sensors to quantum computing. However, only a small library of semi-analytically designed devices are currently known. In this paper, we demonstrate the use of an inverse design method that explores the full design space of fabricable devices and allows us to design devices with previously unattainable functionality, higher performance and robustness, and smaller footprints compared to conventional devices. We designed a silicon wavelength demultiplexer that splits $1300~\mathrm{nm}$ and $1550~\mathrm{nm}$ light from an input waveguide into two output waveguides, and fabricated and characterized several devices. The devices display low insertion loss $\left(2 - 4~\mathrm{dB}\right)$, high contrast $\left(12 - 17~\mathrm{dB}\right)$, and wide bandwidths $\left(\sim 100~\mathrm{nm} \right)$. The device footprint is $2.8 \times 2.8 ~\mathrm{μm}$, making this the smallest dielectric wavelength splitter to date.

physics.optics↗

arXiv2014

Inverse design and implementation of a wavelength demultiplexing grating coupler

Nanophotonics has emerged as a powerful tool for manipulating light on chips. Almost all of today's devices, however, have been designed using slow and ineffective brute-force search methods, leading in many cases to limited device performance. In this article, we provide a complete demonstration of our recently proposed inverse design technique, wherein the user specifies design constraints in the form of target fields rather than a dielectric constant profile, and in particular we use this method to demonstrate a new demultiplexing grating. The novel grating, which has not been developed using conventional techniques, accepts a vertical-incident Gaussian beam from a free-space and separates O-band $(1300\mathrm{nm})$ and C-band $(1550\mathrm{nm})$ light into separate waveguides. This inverse design concept is simple and extendable to a broad class of highly compact devices including frequency splitters, mode converters, and spatial mode multiplexers.

physics.optics↗

arXiv2013

Deterministically Charged Quantum Dots in Photonic Crystal Nanoresonators for Efficient Spin-Photon Interfaces

We demonstrate a novel method for deterministic charging of InAs quantum dots embedded in photonic crystal nanoresonators using a unique vertical p-n-i-n junction within the photonic crystal membrane. Charging is confirmed by the observation of Zeeman splitting for magnetic fields applied in the Voigt configuration. Spectrally resolved photoluminescence measurements are complemented by polarization resolved studies that show the precise structure of the Zeeman quadruplet. Integration of quantum dots in nanoresonators strongly enhances far-field collection efficiency and paves the way for the exploitation of enhanced spin-photon interactions for fabrication of efficient quantum nodes in a scalable solid state platform.

cond-mat.mes-hall↗

arXiv2013

Nanophotonic Computational Design

In contrast to designing nanophotonic devices by tuning a handful of device parameters, we have developed a computational method which utilizes the full parameter space to design linear nanophotonic devices. We show that our method may indeed be capable of designing any linear nanophotonic device by demonstrating designed structures which are fully three-dimensional and multi-modal, exhibit novel functionality, have very compact footprints, exhibit high efficiency, and are manufacturable. In addition, we also demonstrate the ability to produce structures which are strongly robust to wavelength and temperature shift, as well as fabrication error. Critically, we show that our method does not require the user to be a nanophotonic expert or to perform any manual tuning. Instead, we are able to design devices solely based on the users desired performance specification for the device.

physics.optics↗

arXiv2012

Objective-First Nanophotonic Design

We introduce an "objective-first" strategy for designing nanophotonic devices, and we demonstrate the design of nanophotonic coupler, cloak, and mimic devices.

math-ph↗

arXiv2010

Coupled fiber taper extraction of 1.53 um photoluminescence from erbium doped silicon nitride photonic crystal cavities

Optical fiber tapers are used to collect photoluminescence emission at ~1.5 um from photonic crystal cavities fabricated in erbium doped silicon nitride on silicon. Photoluminescence collection via fiber taper is enhanced 2.5 times relative to free space, with a total taper collection efficiency of 53%. By varying the fiber taper offset from the cavity, a broad tuning range of coupling strength is obtained. This material system combined with fiber taper collection is promising for building on-chip optical amplifiers.

physics.optics↗

arXiv2009

Inverse design of nanophotonic structures using complementary convex optimization

A computationally-fast inverse design method for nanophotonic structures is presented. The method is based on two complementary convex optimization problems which modify the dielectric structure and resonant field respectively. The design of one- and two-dimensional nanophotonic resonators is demonstrated and is shown to require minimal computational resources.

physics.optics↗

arXiv2008

Plasmonic Enhancement of Emission from Si-nanocrystals

Plasmonic gratings of different periodicities are fabricated on top of Silicon nanocrystals embedded in Silicon Dioxide. Purcell enhancements of up to 2 were observed, which matches the value from simulations. Plasmonic enhancements are observed for the first three orders of the plasmonic modes, with the peak enhancement wavelength varying with the periodicity. Biharmonic gratings are also fabricated to extract the enhanced emission from the first order plasmonic mode, resulting in enhancements with quality factors of up to 16.

physics.optics↗

arXiv2007

Numerical optimization of a grating coupler for the efficient excitation of surface plasmons at an Ag-SiO2 interface

The efficient generation of surface plasmons from free space optical waves is still an open problem in the field. Here we present a methodology and optimized design for a grating coupler. The photo-excitation of surface plasmons at an Ag-SiO2 interface is numerically demonstrated to yield greater than 50% coupling from a Gaussian beam into surface plasmon voltages and currents.

physics.optics↗