Yanjun Han
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View article: Covariance Alignment: From Maximum Likelihood Estimation to Gromov–Wasserstein
Covariance Alignment: From Maximum Likelihood Estimation to Gromov–Wasserstein Open
View article: Sharp mean-field analysis of permutation mixtures and permutation-invariant decisions
Sharp mean-field analysis of permutation mixtures and permutation-invariant decisions Open
We develop sharp bounds on the statistical distance between high-dimensional permutation mixtures and their i.i.d. counterparts. Our approach establishes a new geometric link between the spectrum of a complex channel overlap matrix and the…
View article: Besting Good--Turing: Optimality of Non-Parametric Maximum Likelihood for Distribution Estimation
Besting Good--Turing: Optimality of Non-Parametric Maximum Likelihood for Distribution Estimation Open
When faced with a small sample from a large universe of possible outcomes, scientists often turn to the venerable Good--Turing estimator. Despite its pedigree, however, this estimator comes with considerable drawbacks, such as the need to …
View article: Over 220 GHz evanescently coupled MUTC-PDs with enhanced responsivity
Over 220 GHz evanescently coupled MUTC-PDs with enhanced responsivity Open
We present evanescently coupled waveguide modified uni-traveling carrier photodiodes (MUTC-PDs) with ultra-wide bandwidth and high responsivity. What we believe to be a novel epitaxial structure incorporating a multilayer input waveguide i…
View article: Evolution of Information in Interactive Decision Making: A Case Study for Multi-Armed Bandits
Evolution of Information in Interactive Decision Making: A Case Study for Multi-Armed Bandits Open
We study the evolution of information in interactive decision making through the lens of a stochastic multi-armed bandit problem. Focusing on a fundamental example where a unique optimal arm outperforms the rest by a fixed margin, we chara…
View article: Joint Value Estimation and Bidding in Repeated First-Price Auctions
Joint Value Estimation and Bidding in Repeated First-Price Auctions Open
We study regret minimization in repeated first-price auctions (FPAs), where a bidder observes only the realized outcome after each auction -- win or loss. This setup reflects practical scenarios in online display advertising where the actu…
View article: Reconfigurable nonlinear optical computing device for retina-inspired computing
Reconfigurable nonlinear optical computing device for retina-inspired computing Open
Optical neural networks are at the forefront of computational innovation, utilizing photons as the primary carriers of information and employing optical components for computation. However, the fundamental nonlinear optical device in the n…
View article: Fabrication-integrated design for diffractive optical elements
Fabrication-integrated design for diffractive optical elements Open
Grayscale direct laser writing lithography (DLWL) is a versatile technique for fabricating diffractive optical elements (DOEs), which play a critical role in controlling light across diverse optical applications. However, optical proximity…
View article: Approximate independence of permutation mixtures
Approximate independence of permutation mixtures Open
We prove bounds on statistical distances between high-dimensional exchangeable mixture distributions (which we call \emph{permutation mixtures}) and their i.i.d. counterparts. Our results are based on a novel method for controlling $χ^2$ d…
View article: Ultrafast evanescently coupled waveguide MUTC-PDs with high responsivity
Ultrafast evanescently coupled waveguide MUTC-PDs with high responsivity Open
Novel evanescently coupled waveguide modified uni-traveling carrier photodiodes (MUTC-PDs) employing a thick multi-layer coupling waveguide are reported. To improve the optical-to-electrical (O/E) conversion efficiency, a thick multi-layer…
View article: Stochastic contextual bandits with graph feedback: from independence number to MAS number
Stochastic contextual bandits with graph feedback: from independence number to MAS number Open
We consider contextual bandits with graph feedback, a class of interactive learning problems with richer structures than vanilla contextual bandits, where taking an action reveals the rewards for all neighboring actions in the feedback gra…
View article: Covariance alignment: from maximum likelihood estimation to Gromov-Wasserstein
Covariance alignment: from maximum likelihood estimation to Gromov-Wasserstein Open
Feature alignment methods are used in many scientific disciplines for data pooling, annotation, and comparison. As an instance of a permutation learning problem, feature alignment presents significant statistical and computational challeng…
View article: Extended ray-mapping method based on differentiable ray-tracing for non-paraxial and off-axis freeform illumination lens design
Extended ray-mapping method based on differentiable ray-tracing for non-paraxial and off-axis freeform illumination lens design Open
The ray-mapping method has been widely used for designing freeform illumination lenses. However, in non-paraxial or off-axis situations, it remains challenging to obtain an integrable ray-mapping, often requiring a complex iterative correc…
View article: Ultrafast MUTC photodiodes over 200 GHz with high saturation power
Ultrafast MUTC photodiodes over 200 GHz with high saturation power Open
Novel back-illuminated modified uni-traveling-carrier photodiodes (MUTC-PDs) with wide bandwidth and high saturation power are demonstrated. The effect of cliff layer doping on the electric field distribution is investigated to achieve fas…
View article: Synchrophasor-based Online State Estimated in Large-scale Power Grid
Synchrophasor-based Online State Estimated in Large-scale Power Grid Open
With integration of a larger amount of clean power sources and power electronic equipment, operation and dynamic characteristics of the power grid are becoming more and more complicated and stochastic.Therefore, it is necessary and urgent …
View article: Metal organic vapor phase epitaxy of high-indium-composition InGaN quantum dots towards red micro-LEDs
Metal organic vapor phase epitaxy of high-indium-composition InGaN quantum dots towards red micro-LEDs Open
Micro-scale light-emitting diodes (micro-LEDs) are regarded as the next generation display technology. Compared to blue and green ones, InGaN-based red micro-LEDs require higher indium composition in their active region, which is quite cha…
View article: Membrane multiple quantum well electro-optical modulator employing low loss high-k radio-frequency slot waveguides
Membrane multiple quantum well electro-optical modulator employing low loss high-k radio-frequency slot waveguides Open
A membrane multiple quantum well (MQW) electro-optical (EO) modulator exploiting low loss high-k radio-frequency (RF) slot waveguides is proposed for sub-terahertz bandwidth. By employing high-k barium titanate (BTO) claddings in place of …
View article: Ultrafast parallel single-pixel LiDAR with all-optical spectro-temporal encoding
Ultrafast parallel single-pixel LiDAR with all-optical spectro-temporal encoding Open
Light detection and ranging (LiDAR) with scanning beam has been widely used in autonomous driving and large-scale manufacturing, where the fast-changing scene is of great interest. However, the acquisition rate of current LiDAR is limited …
View article: A high-Q mid-infrared Tamm plasmon absorber using MgF2 and Ge aperiodic tandem films designed by the genetic algorithm
A high-Q mid-infrared Tamm plasmon absorber using MgF2 and Ge aperiodic tandem films designed by the genetic algorithm Open
A high-Q mid-infrared Tamm plasmon (TP) absorber using MgF2 and Ge aperiodic tandem films is designed by the genetic algorithm and fabricated by electron beam evaporation and magnetron sputtering. Such a design circumvents the need for the…
View article: Noise-immune image blur detection via sequency spectrum truncation
Noise-immune image blur detection via sequency spectrum truncation Open
Blur detection is aimed to differentiate the blurry and sharp regions from a given image. This task has attracted much attention in recent years due to its importance in computer vision with the integration of image processing and artifici…
View article: Sub-terahertz bandwidth capactively-loaded thin-film lithium niobate electro-optic modulators based on an undercut structure
Sub-terahertz bandwidth capactively-loaded thin-film lithium niobate electro-optic modulators based on an undercut structure Open
A thin film lithium niobate (TFLN) electro-optic modulator based on a partially removed benzocyclobutene (BCB) bonding layer is proposed for sub-terahertz bandwidth. Low-loss microwave transmission is realized by periodic capacitively load…
View article: Low loss hybrid plasmon polariton Mach-Zehnder modulators
Low loss hybrid plasmon polariton Mach-Zehnder modulators Open
We propose a hybrid plasmon polariton (HPP) Mach-Zehnder modulator (MZM) structure that combines the tight optical confinement of plasmonic waveguides and narrow slot waveguides with the low loss feature of photonic waveguides. Compared wi…
View article: Geometric Lower Bounds for Distributed Parameter Estimation Under Communication Constraints
Geometric Lower Bounds for Distributed Parameter Estimation Under Communication Constraints Open
We consider parameter estimation in distributed networks, where each sensor in the network observes an independent sample from an underlying distribution and has $k$ bits to communicate its sample to a centralized processor which computes …
View article: Optimal prediction of Markov chains with and without spectral gap
Optimal prediction of Markov chains with and without spectral gap Open
We study the following learning problem with dependent data: Observing a trajectory of length $n$ from a stationary Markov chain with $k$ states, the goal is to predict the next state. For $3 \leq k \leq O(\sqrt{n})$, using techniques from…
View article: Planar multi-aperture fish-eye lens using metagrating
Planar multi-aperture fish-eye lens using metagrating Open
The design of compact optical systems with large field of view has been difficult due to the requirement of many elements or a curved focal plane to reduce off-axis aberration. We propose a multi-aperture lens design to effectively resolve…
View article: Ultrafast Parallel LiDAR with Time-encoding and Spectral Scanning: Breaking the Time-of-flight Limit
Ultrafast Parallel LiDAR with Time-encoding and Spectral Scanning: Breaking the Time-of-flight Limit Open
Light detection and ranging (LiDAR) has been widely used in autonomous driving and large-scale manufacturing. Although state-of-the-art scanning LiDAR can perform long-range three-dimensional imaging, the frame rate is limited by both roun…
View article: Provably Breaking the Quadratic Error Compounding Barrier in Imitation Learning, Optimally
Provably Breaking the Quadratic Error Compounding Barrier in Imitation Learning, Optimally Open
We study the statistical limits of Imitation Learning (IL) in episodic Markov Decision Processes (MDPs) with a state space $\mathcal{S}$. We focus on the known-transition setting where the learner is provided a dataset of $N$ length-$H$ tr…
View article: A single-chip multi-beam steering optical phased array: design rules and simulations
A single-chip multi-beam steering optical phased array: design rules and simulations Open
A waveguide-based multi-beam steering device is proposed for light detection and ranging (LIDAR). The device integrates binary gratings with an optical phased array (OPA), thus enabling a single-chip LIDAR system. The device can provide an…
View article: Low half-wave-voltage, ultra-high bandwidth thin-film LiNbO3 modulator based on hybrid waveguide and periodic capacitively loaded electrodes
Low half-wave-voltage, ultra-high bandwidth thin-film LiNbO3 modulator based on hybrid waveguide and periodic capacitively loaded electrodes Open
A novel thin-film LiNbO3 (TFLN) electro-optic modulator is proposed and demonstrated. LiNbO3-silica hybrid waveguide is adopted to maintain low optical loss for an electrode spacing as narrow as 3 μm, resulting in a record low half-wave-vo…
View article: Adversarial Combinatorial Bandits with General Non-linear Reward Functions
Adversarial Combinatorial Bandits with General Non-linear Reward Functions Open
In this paper we study the adversarial combinatorial bandit with a known non-linear reward function, extending existing work on adversarial linear combinatorial bandit. {The adversarial combinatorial bandit with general non-linear reward i…