Stefano Longhi
A general analysis of undistorted propagation of localized wavepackets in photonic crystals based on a Wannier-function expansion technique is presented. Different kinds of propagating and stationary spatio-temporal localized waves are found from an asymptotic analysis of the Wannier function envelope equation.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
继续探索
In this work, we use Wannier functions to analyze topological phase transitions in one dimensional photonic crystals. We first review the construction of exponentially localized Wannier functions in one dimension, and show how to numerically construct them for photonic systems. We then apply these tools to study a photonic analog of the Su-Schrieffer-Heeger model. We use photonic Wannier functions to construct a quantitatively accurate approximate model for the topological phase transition, and compute the localization of topological defect states. Finally, we discuss the implications of our w…
In the presence of crystalline symmetries, second-order topological insulators can be featured by the polarization which is believed identical to the Wannier center. In this Letter, we show that second-order topological insulators are present in the full process of topological phase transition between a pair of degenerate photonic bands resulting from the non-symmorphic glide symmetry in all-dielectric photonic crystals. Due to the coupling (hybridization) of the Wannier functions, the center of the maximally localized Wannier function always locates at the origin, not equal to the addition of…
Photonic crystals have provided a controllable platform to examine excitingly new topological states in open systems. In this work, we reveal photonic topological corner states in a photonic graphene with mirror-symmetrically patterned gain and loss. Such a nontrivial Wannier-type higher-order topological phase is achieved through solely tuning on-site gain/loss strengths, which leads to annihilation of the two valley Dirac cones at a time-reversal-symmetric point, as the gain and loss change the effective tunneling between adjacent sites. We find that the symmetry-protected photonic corner mo…
Wannier function expansions are well suited for the description of photonic- crystal-based defect structures, but constructing maximally localized Wannier functions by optimizing the phase degree of freedom of the Bloch modes is crucial for the efficiency of the approach. We systematically analyze different locality criteria for maximally localized Wannier functions in two- dimensional square and triangular lattice photonic crystals, employing (local) conjugate-gradient as well as (global) genetic-algorithm-based, stochastic methods. Besides the commonly used second moment (SM) locality measur…
We observe Wannier-Stark localization in curved photonic lattices, realized using arrays of evanescently coupled optical waveguides. By correctly tuning the strength of inter-site coupling in the lattice, we observe that Wannier-Stark states become increasingly localized, and eventually fully localized to one site, as the curvature of the lattice is increased. We then demonstrate that tunneling can be successfully restored in the lattice by applying a sinusoidal modulation to the lattice position, an effect that is a direct analogue of photon-assisted tunneling. This precise tuning of the tunn…
Topological Corner Modes by Composite Wannier States in Glide-Symmetric Photonic Crystal
本文在滑移对称全介质光子晶体中利用部分简并能带和复合万尼尔态实现二阶拓扑绝缘体，通过数值模拟与微波实验证实拓扑角模，为集成与量子光子学中的高阶拓扑研究提供新途径。
Quench dynamics of Wannier-Stark states in an active synthetic photonic lattice
本文提出以调制环形快增益激光器构建等密度填充的合成光子晶格，实现并观测 Wannier-Stark 梯淬火后的振荡及其向单态的相干稳定。
The fundamental building blocks in band theory are band representations (BRs): bands whose infinitely-numbered Wannier functions are generated (by action of a space group) from a finite number of symmetric Wannier functions centered on a point in space. This work aims to simplify questions on a multi-rank BR by splitting it into unit-rank bands, via the following crystallographic splitting theorem: being a rank-$N$ BR is equivalent to being splittable into a finite sum of bands indexed by $\{1,2,\ldots,N\}$, such that each band is spanned by a single, analytic Bloch function of $k$, and any sy…
We generalize the concept of nonlinear periodic structures to systems that show arbitrary spacetime variations of the refractive index. Nonlinear pulse propagation through these spatiotemporal photonic crystals can be described, for shallow nonstationary gratings, by coupled mode equations which are a generalization of the traditional equations used for stationary photonic crystals. Novel gap soliton solutions are found by solving a modified massive Thirring model. They represent the missing link between the gap solitons in static photonic crystals and resonance solitons found in dynamic grati…
A detailed analysis is presented of the modes of a class of spatiotemporal photonic crystal. The structure analyzed is a perfect dielectric with periodic variation of ε in a single spatial direction, as well as periodic variation in time. Analytic solutions are presented for ε being separated in both variables, that is ε(z,t)=ε0εr(z)εt(t), and dispersion diagrams are presented.
Spatiotemporal Photonic Emulator of Potential-free Schrödinger Equation
本研究提出一种基于球谐对称时空局域波包的新型无势场薛定谔方程光子量子模拟器，实验验证了其局域特性，可为量子物理及相关光学领域研究提供新方向。
Coexistence of extended and localized states in finite-sized mosaic Wannier-Stark lattices
该研究利用硅光子平台实现无无序马赛克 Wannier-Stark 晶格，并通过合成电场实验证明有限尺寸系统中强局域态与弱局域导电态可依赖能量共存。
Spatiotemporal Hologram
针对时空光难以同时调控振幅与相位的问题，提出一种通用时空全息方法，可任意定制多种时空波包并服务于光-物质相互作用研究。
Spatiotemporal topological phase transitions in photonic spacetime crystals
本研究首次在光子时空晶体中实现时空拓扑相变，通过动态调制超材料观察到能量和动量带隙的闭合与重新开启，揭示了时空与拓扑的相互作用。
Quadrupole topological phases, exhibiting protected boundary states that are themselves topological insulators of lower dimensions, have recently been of great interest. Extensions of these ideas from current tight binding models to continuum theories for realistic materials require the identification of quantized invariants describing the bulk quadrupole order. Here we identify the analog of quadrupole order in Maxwell's equations for a photonic crystal (PhC) and identify quadrupole topological photonic crystals formed through a band inversion process. Unlike prior studies relying on threaded…
STEPIC: High-Speed Imaging via Spatio-Temporal Encoding in Photonic Integrated Circuits
提出首个全集成片上系统STEPIC显微镜，利用光子集成电路中的波导、分束器、光纤延迟线和3D光学重映射器实现时空编码，从而对微通道中流动的细胞进行高速成像，提供紧凑稳健的高通量生物成像平台。
Continuous-variable spatio-spectral quantum networks in nonlinear photonic lattices
本文提出利用非线性光子晶格生成连续变量纠缠，解决光学量子通信的可扩展性问题，并展示其在量子通信网络中的应用潜力。
Spatiotemporal Topological Phase Transition in non-Hermitian Photonic System
本研究通过非厄米特SSH模型实现时空拓扑相变，展示了在静态平台中统一能量与动量间隙的连续过渡，并实验验证了时空拓扑相变的实时控制。
Spatio-temporal imaging of light propagation is very important in photonics because it provides the most direct tool available to study the interaction between light and its host environment. Sub-ps time resolution is needed to investigate the fine and complex structural features that characterize disordered and heterogeneous structures, which are responsible for a rich array of transport physics that have not yet been fully explored. A newly developed wide-field imaging system enables us to present a spatio-temporal study on light transport in various disordered media, revealing properties th…
Today, it is well known that light possesses a linear momentum which is along the propagation direction. Besides, scientists also discovered that light can possess an angular momentum (AM), a spin angular momentum (SAM) associated with circular polarization and an orbital angular momentum (OAM) owing to the azimuthally dependent phase. Even though such angular momenta are longitudinal in general, a SAM transverse to the propagation has opened up a variety of key applications [1]. In contrast, investigations of the transverse OAM are quite rare due to its complex nature. Here we demonstrate a s…
Symmetry Breaking and Spatiotemporal Pattern Formation in Photonic Time Crystals
本文研究了具有光学Kerr非线性的时变光子介质的相变动力学，发现介电常数周期调制与非线性作用导致电磁波进入时空平移对称性破缺状态，形成类晶格图样并激发类Goldstone和Higgs模，同时将该分析扩展至2+1维时变介质。
Thouless Pumping of Wave Action in Photonic Time Crystals
本文研究光子时间晶体中波作用的拓扑泵浦，通过连接带拓扑与波作用的时间位移，发现绝热周期内中心位移等于带陈数，揭示了拓扑输运的新机制。
High-order topological phases, such as those with nontrivial quadrupole moments, protect edge states that are themselves topological insulators in lower dimensions. So far, most quadrupole phases of light are explored in linear optical systems, which are protected by spatial symmetries or synthetic symmetries. Here we present Floquet quadrupole phases in driven nonlinear photonic crystals (PhCs) that are protected by space-time screw symmetries. We start by illustrating space-time symmetries by tracking the trajectory of instantaneous optical axes of the driven media. Our Floquet quadrupole ph…
Excitons: Energetics and spatio-temporal dynamics
本文综述了激子在复杂系统中的能量学与时空动力学研究，探讨了其在纳米材料、多色基大分子等复杂结构中的行为及影响因素。
Spatio-Temporal Photonic Metalattice
该研究通过将空间图案化与超快脉冲诱导的时间晶格结合，在透明导电薄膜中实现二维时空金属晶格，利用三次谐波产生动态可重构衍射，为超快可重构光子学开辟新途径。
The growing diffusion of integrated photonic technologies requires fast and non-invasive quality control techniques for mass-production. We present a general diagnostic technique for sub-ps imaging of photonic circuits combining wide-field optical microscopy and optical gating. The simultaneous access to multiple parameters of a photonic structure enables an unprecedented characterization of its functional design as opposed to typical single-domain techniques such as frequency or time domain reflectometry and near-field microscopy. The non-contact and non-perturbative nature of the technique m…
Topological Quantum Chemistry (TQC) has recently emerged as a instrumental tool to characterize the topological nature of both fermionic and bosonic band structures. TQC is based on the study of band representations and the localization of maximally localized Wannier functions. In this article, we study various two-dimensional photonic crystal structures analyzing their topological character through a combined study of TQC, their Wilson-loop spectra and the electromagnetic energy density. Our study demonstrates that the analysis of the spatial localization of the energy density complements the…
Overcoming Intrinsic Dispersion Locking for Achieving Spatio-Spectral Selectivity with Misaligned Bi-metagratings
针对周期结构中波矢与波长的本征色散锁定问题，提出利用角度依赖辐射方向性与 Fano 干涉的错位双层 metagrating，实现单频、单角度窄带完美反射及高对比度空间-光谱成像。
Interface States in Space-Time Photonic Crystals: Topological Origin, Propagation and Amplification
本文提出了一种研究时空光子晶体中界面态的框架，通过时空对称性分析揭示其拓扑起源，并展示了亚光速和超光速边界下的独特传播与放大特性。
Non-Bloch Theory for Spatiotemporal Photonic Crystals Assisted by Continuum Effective Medium
针对时空关联限制非布洛赫能带理论应用的问题，提出有效介质辅助的方法，建立了时空调制材料光子晶体的低频Floquet能带非布洛赫理论，并解析了其拓扑性质。
Emerging photonic functionalities are mostly governed by the fundamental principle of Lorentz reciprocity. Lifting the constraints imposed by this principle could circumvent deleterious effects that limit the performance of photonic systems. A variety of approaches have recently been explored to break reciprocity, yet most efforts have been limited to confined photonic systems. Here, we propose and experimentally demonstrate a spatio-temporally modulated metasurface capable of extreme breakdown of Lorentz reciprocity. Through tailoring the momentum and frequency harmonic contents of the scatte…
Temporal condensed matter physics in gas-filled photonic crystal fibers
本研究发现充气空芯光子晶体光纤中拉曼效应诱导的脉冲传输方程与周期势场电子的凝聚态问题时空互换后等价，证明可通过纯光学方式在时域实现Wannier-Stark梯等典型凝聚态现象。
Transversality-Enforced Tight-Binding Models for 3D Photonic Crystals aided by Topological Quantum Chemistry
本文利用拓扑量子化学和辅助模式克服三维光子晶体中 Maxwell 横波条件对 Wannier 基组构建的阻碍，提出横波条件强制紧束缚模型，首次系统解析模拟整个 Brillouin 区最低横模的光子能带。
Obstructed Atomic Limit Topological Protection in C4-Symmetric Photonic Crystals for Optical Communications
本研究探讨了C4对称光子晶体中受阻原子极限间极化失配诱导的界面局域模式，展示了其在结构扰动下的高透射与近乎无损传输，为光通信中鲁棒光子传输提供了实用机制。
Topological manipulation of waves is at the heart of the cutting-edge metamaterial researches. Quadrupole topological insulators were recently discovered in two-dimensional (2D) flux-threading lattices which exhibit higher-order topological wave trapping at both the edges and corners. Photonic crystals (PhCs), lying at the boundary between continuous media and discrete lattices, however, are incompatible with the present quadrupole topological theory. Here, we unveil quadrupole topological PhCs triggered by a twisting degree-of-freedom. Using a topologically trivial PhC as the motherboard, we …
In the research of topological phases of matter, valley pseudospins have been introduced into photonic systems. Here, we construct a split-ring photonic crystal (SPC) in which the spilt rings are distributed according to the Kagome model. By rotating three split rings as a whole under the condition of ensuring the existence of C3v symmetry, we obtain a traditional two-band-inversion valley topology (2IVT) driven by opening twofold Dirac degeneracy point. When three split rings are rotated as a whole without ensuring the existence of C3v symmetry, a valley-like topology driven by opening twofol…
A single Dirac cone on the surface is the hallmark of three-dimensional (3D) topological insulators, where the double degeneracy at the Dirac point is protected by time-reversal symmetry and the spin-splitting away from the point is provided by the spin-orbital coupling. Here we predict a single Dirac-cone surface state in a 3D photonic crystal, where the degeneracy at the Dirac point is protected by a nonsymmorphic glide reflection and the linear splitting away from it is enabled by breaking time-reversal symmetry. Such a gapless surface state is fully robust against random disorder of any ty…
Dynamic Chirality in Photonic Time Crystals
提出时空光子时间晶体，通过方位角行波介电调制实现合成旋转，解除模态简并产生手性模式，实现可调圆二色性，为无机械运动可重构手性光子学提供新策略。
We have developed an analytical model based on the perturbation theory in order to study the optical propagation of two successive intense solitons in hollow-core photonic crystal fibers filled with Raman-active gases. Based on the time delay between the two solitons, we have found that the trailing soliton dynamics can experience unusual nonlinear phenomena such as spectral and temporal soliton oscillations and transport towards the leading soliton. The overall dynamics can lead to a spatiotemporal modulation of the refractive index with a uniform temporal period and a uniform or chirped spat…
Single-shot 3D characterization the spatiotemporal optical vortex via a spatiotemporal wavefront sensor (STWFS)
本文提出一种时空波前传感器，实现单次成像三维表征时空光学涡旋，提供高精度相位重建和超快三维诊断。
An ultrafast diamond nonlinear photonic sensor
本研究提出了一种超快钻石非线性光子传感器，用于高精度检测纳米级材料的电场变化。
Spatiotemporal computing for temporal nonlinear tasks using few-mode fiber and SOA nonlinearity
该研究利用少模光纤（FMF）结合半导体光放大器（SOA）的非线性，构建时空计算架构，在28.5 Gb/s速率下完成延迟异或和高阶奇偶校验等非线性任务，通过多时间样本特征提升分类性能。
Breathing k-Gap Events and Instability on Instability in Nonlinear Photonic Time Crystals
研究非线性光子时间晶体中 k 间隙相关现象，通过局部扰动引发呼吸 k 间隙事件，此事件从孤子中提取能量并靠相互作用维持，对噪声和无序鲁棒，可通过特定播种控制，确立了 k 间隙工程用于产生和控制时空波的途径。
Spatiotemporal coupled Airy-Airy wavepacket and its propagation dynamics
本文首次生成并控制时空耦合 Airy-Airy 波包，在保持垂直分布的同时实现旋转，并验证其自加速与自愈特性，为超快激光管理、光学微操控和时域编码通信提供新策略。
For a scalable photonic device producing entangled photons, it is desirable to have multiple quantum emitters in an ensemble that can be collectively excited, despite their spectral variability. For quantum dots, Rabi rotation, the most popular method for resonant excitation, cannot assure a universal, highly efficient excited state preparation, because of its sensitivity to the excitation parameters. In contrast, Adiabatic Rapid Passage (ARP), relying on chirped optical pulses, is immune to quantum dot spectral inhomogeneity. Here, we advocate the robustness of ARP for simultaneous excitation…
We analyze the propagation of electromagnetic waves in media where the dielectric constants undergo rapid temporal periodic modulation. Both spatially homogeneous and periodic media are studied. Fast periodic temporal modulation of the dielectric constant of a homogeneous medium leads to existence of photonic band-gap like phenomena. In the presence of both spatial and tem- poral periodicity the electromagnetic spectrum is described in a four-dimensional cube, defining an effective Brillouin zone. In the case of incommensurability between space and time periodicities, completely dispersed poin…
General Framework for Twisted Bilayer Photonic Crystal with Interlayer Coupling and Far-Field Response
本文构建兼顾近场层间耦合与远场响应的扭转双层光子晶体通用理论，解释能带劈裂与散射抑制，并提出可调谐高 Q 平带腔。
Introducing precise spatio-temporal structure into a pulsed optical field can lead to remarkable changes with its free propagation. `Space-time' (ST) wave packets, for example, propagate rigidly at a tunable group velocity in free space by inculcating a one-to-one relationship between the axial wave numbers and the temporal frequencies. Here we introduce a new class of ST wave packets that we call V-waves (so named because of their characteristically V-shaped spatio-temporal spectrum) in which a linear one-to-one relationship is introduced between the temporal frequencies and the transverse wa…
We report the use of prism-assisted side-coupling to investigate the spatio-temporal dynamics of photoionization in an Ar-filled hollow-core photonic crystal fiber. By launching four different LP core modes we are able to probe temporal and spatial changes in the modal refractive index on timescales from a few hundred picoseconds to several hundred microseconds after the ionization event. We experimentally analyze the underlying gas density waves and find good agreement with quantitative and qualitative hydrodynamic predictions. Moreover, we observe periodic modulations in the MHz-range lastin…
Three Dimensional Reconfigurable Optical Singularities in Bilayer Photonic Crystals
本文提出利用可调谐双层光子晶体实现三维可重构光学奇点，动态调制了连续域束缚态与轨道角动量，为多维偏振和相位控制提供了新方向。
Generating and Weaving Topological Event Wavepackets in Photonic Spacetime Crystals with Fully Energy-Momentum Gapped
本文提出光子时空晶体中的拓扑事件波包，利用完全打开的能量-动量带隙实现强时空局域和拓扑保护，并通过时空卷绕数阐明保护机制，还展示了周期编织形成事件晶格以抑制噪声放大，为微波到光学波段的波动操控提供新途径。
Nonlinear wave dynamics in photonic time crystals
该研究通过解析简化麦克斯韦方程得到非线性马蒂厄方程，推导同宿分界线等参数，揭示时空带隙孤子成核可产生动量空间超连续谱，建立了非线性光子时间晶体中相关动力学的直接联系。
The multiple scattering of coherent light is a problem of both fundamental and applied importance. In optics, phase conjugation allows spatial focussing and imaging through a multiply scattering medium; however, temporal control is nonetheless elusive, and multiple scattering remains a challenge for femtosecond science. Here, we report on the spatially and temporally resolved measurement of a speckle field produced by the propagation of an ultrafast optical pulse through a thick strongly scattering medium. Using spectral pulse shaping, we demonstrate the spatially localized temporal recompress…
Absence of topological protection of the interface states in $\mathbb{Z}_2$ photonic crystals
本文利用拓扑量子化学工具证明 Wu-Hu 光子晶体模型在拓扑上是平庸的，其界面态可被对称微扰打开能隙，揭示了拓扑性并非光子系统中螺旋边缘态的必要条件。
Space-Time Hopfion Crystals
本文针对霍普夫离子在高密度信息领域的应用潜力，提出利用时空结构化光构建时空霍普夫离子晶体，通过双色光束或偶极子阵列组装高维霍普夫离子晶格并定制拓扑序，为高维鲁棒拓扑信息处理开辟新方向。
Combined spatially and temporally multiplexed photonic reservoir computer with a diffractively coupled VCSEL-array
本文提出一种结合空间和时间多路复用的光子共振计算机，通过外部腔体的衍射耦合激光实现空间和时间多路复用，提升分类性能和网络可扩展性。
Parity-time symmetry phase transition in photonic time-modulated media
本文研究时间调制光子介质中的时间宇称-时间对称性，证明其是获得实本征值谱的必要非充分条件，并揭示介电常数实虚部调制深度对比决定相变，通过Magnus展开和全波模拟验证了该相变。
Spatio-Temporal Nonlinear Theory in Birefringent Microrings
针对双折射微环非线性过程转换效率缺乏理论分析的问题，本文引入时空耦合模方程描述腔模空间特性，发现X切铌酸锂微环可在宽频范围不同方位角实现强二次谐波产生，为高效双折射光子集成电路设计提供指导。
Topologically-protected superluminal pair annihilation in photonic time crystals
本文在光子时间晶体中引入时间Jackiw-Rebbi扭结，实现拓扑保护的相位选择性粒子对湮灭，表现为超光速级联但保持因果性，并构建非厄米晶格模型验证，为时变介质波操控提供新机制。
Deterministic Free-Propagating Photonic Qubits with Negative Wigner Functions
本文利用腔内 Rydberg 超原子到单光子量子比特的态映射，首次确定性制备自由传播的 Wigner 负非高斯光态，实现60%产生效率和强反聚束。
扫码添加微信好友，提出您的宝贵建议 👇
💡 备注请填写：网站反馈
发表机构由 AI 从论文文本抽取，如发现错误，欢迎反馈修正建议。