Juan C. Gonzalez, Juan C. Minano, Pablo Benitez
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.
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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…
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。
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。
Photonic neural networks with spatiotemporal chaos in multimode fibers
本研究提出利用梯度折射率多模光纤内时空混沌的光子神经网络，经模拟与实验验证其可提升多领域分类准确率，为高效可扩展的光学计算架构提供新思路。
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…
Photonic accelerators have attracted increasing attention in artificial intelligence applications. The multi-armed bandit problem is a fundamental problem of decision making using reinforcement learning. However, the scalability of photonic decision making has not yet been demonstrated in experiments, owing to technical difficulties in physical realization. We propose a parallel photonic decision-making system for solving large-scale multi-armed bandit problems using optical spatiotemporal chaos. We solve a 512-armed bandit problem online, which is much larger than previous experiments by two …
Dissipative Kerr soliton (DKS) frequency combs - also known as microcombs - have arguably created a new field in cavity nonlinear photonics, with a strong cross-fertilization between theoretical, experimental, and technological research. Spatiotemporal mode-locking (STML) not only add new degrees of freedom to ultrafast laser technology, but also provide new insights for implementing analogue computers and heuristic optimizers with photonics. Here, we combine the principles of DKS and STML for the first time to demonstrate the STML DKS by developing an unexplored ultrahigh-quality-factor Fabry…
We develop a class of supercell photonic crystals supporting complete photonic bandgaps based on breaking spatial symmetries of the underlying primitive photonic crystal. One member of this class based on a two-dimensional honeycomb structure supports a complete bandgap for an index-contrast ratio as low as $n_{high}/n_{low} = 2.1$, making this the first such 2D photonic crystal to support a complete bandgap in lossless materials at visible frequencies. The complete bandgaps found in such supercell photonic crystals do not necessarily monotonically increase as the index-contrast in the system …
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。
We introduce a small-core air-guiding photonic crystal fiber whose cladding is made of improved air-silica photonic crystal with non-circular air holes placed in triangular lattice. The fiber achieves un-disturbed bandgap guidance over 350nm wavelength range.
The presence of topological edge modes at the interface of two perturbed honeycomb photonic crystals with $C_6$ symmetry is often attributed to the different signs of Berry curvature at the K and K$'$ valleys. In contrast to the electronic counterpart, the Chern number defined in photonic valley Hall effect is not a quantized quantity but can be tuned to finite values including zero simply by changing geometrical perturbations. Here, we argue that the edge modes in photonic valley Hall effect can exist even when Berry curvature vanishes. We numerically demonstrate the presence of the zero-Berr…
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。
We report on the fabrication and characterization of photonic-based nanothermometers, a silicon photonic Bragg grating and photonic crystal cavity. When cladded with silicon dioxide layer the sensors have at least eight times better sensitivity compared to the sensitivity of conventional fiber Bragg grating sensors. We demonstrate that these photonic thermometers are a viable temperature sensing solution.
We introduce a new "universality class" of artificial optical media - photonic hyper-crystals. These hyperbolic metamaterials with periodic spatial variation of dielectric permittivity on subwavelength scale, combine the features of optical metamaterials and photonic crystals. In particular, surface waves supported by a hyper-crystal, possess the properties of both the optical Tamm states in photonic crystals and surface plasmon polaritons at the metal-dielectric interface.
In this paper we proposed a novel overlay alignment method using two sets of identical photonic crystals (PhCs). In this method the reflection or transmission spectrum of the two overlaid photonic crystals is measured to help wafer tilt, yaw rotation, and translation aligning. The initial testing results with two 1D photonic crystals and analysis of the alignment accuracy are presented. This method is particularly useful in building photonic crystal stacks with nanoimprint lithography (NIL).
We describe a semi-analytical approach for three-dimensional analysis of photonic crystal fibre devices. The approach relies on modal transmission-line theory. We offer two examples illustrating the utilization of this approach in photonic crystal fibres: the verification of the coupling action in a photonic crystal fibre coupler and the modal reflectivity in a photonic crystal fibre distributed Bragg reflector.
Kossel diffraction under standing-wave excitation in a one-dimensional photonic crystal is investigated. It is shown that by combining the reciprocity theorem, the Fermi golden rule and the concept of density of photonic modes, it is possible to predict the behaviour of the Kossel diffraction in such a system.
We report systematic studies of plasmonic and photonic guiding modes in large-area chemical-vapor-deposition-grown graphene on nanostructured silicon substrates. Light interaction in graphene with substrate photonic crystals can be classified into four distinct regimes depending on the photonic crystal lattice constant and the various modal wavelengths (i.e. plasmonic, photonic and free-space). By optimizing the design of the substrate, these resonant modes can magnify the graphene absorption in infrared wavelength, for efficient modulators, filters, sensors and photodetectors on silicon photo…
In this work, it has been investigated whether photonic density of states maps can be applied to the design of photonic crystal-based devices. For this reason, comparison between photonic density of states maps and transmittance maps was carried out. Results of comparison show full correspondence between these characteristics. Photonic density of states maps appear to be preferable for the design of photonic crystal devices, than photonic band gap maps presented earlier and than transmittance maps shown in the paper.
I studied experimentally the beam self-collimation and splitting in two-dimensional microwave photonic crystals. Using a microwave photonic crystal fabricated from alumina rods, I present an experimental proof of principle for an earlier theoretical proposal [A. Matthews et al., Opt. Commun. 279, 313 (2007)] of a photonic crystal beam splitter based on the self-collimation effect.
In this paper, we present a simple, yet versatile, analytical model of one-dimensional photonic crystal (1D PC). In our theoretical model, we take into account direction of propagation and therefore do not neglect anisotropic nature of photonic crystals. We derive analytical expressions for mode spectrum and density of states in 1D photonic crystal. With those formulas, we obtain mode spectrum characteristics, which depict formation of photonic band gap and reveal properties of photonic crystals.
Here, the frequency degree of freedom is introduced into valley photonic crystals with dual band gaps. Based on the high-order plane wave expansion model, we derive an effective Hamiltonian which characterizes dual band gaps. Metallic valley photonic crystals are demonstrated as examples in which all four topological phases are found. At the domain walls between topologically distinct valley photonic crystals, frequency-dependent edge states are demonstrated and a broadband photonic detouring is proposed. Our findings provide the guidance for designing the frequency-dependent property of topol…
Interface states in a 1-D photonic crystal heterostructure with multiple interfaces are examined. It is found that the behavior of the localized modes in the photonic band gaps is dependent on whether there is an even or odd number of photonic crystal interfaces in the heterostructure. With certain sequences of all dielectric photonic crystals, topological states are shown to split in two, whereas for other heterostructures they are shown to vanish. Additional resonant modes appear depending on how many crystals are in the heterostructure.
In this paper, we have proposed a new compound structure one-dimensional photonic crystal, which include series connection, parallel connection and positive and negative feedback compound structure photonic crystal. We have studied their transmission characteristics and obtained some new results, which should be help to design new type optical devices, such as optical amplifier, photonic crystal laser and so on.
We consider chromatic dispersion of capillary tubes and photonic crystal fibers infiltrated with liquid crystals. A perturbative scheme for inclusion of material dispersion of both liquid crystal and the surrounding waveguide material is derived. The method is used to calculate the chromatic dispersion at different temperatures.
In this paper, we have firstly proposed two-dimensional function photonic crystals, which the dielectric constants of medium columns are the functions of space coordinates $\vec{r}$, it is different from the two-dimensional conventional photonic crystals constituting by the medium columns of dielectric constants are constants. We find the band gaps of two-dimensional function photonic crystals are different from the two-dimensional conventional photonic crystals, and when the functions form of dielectric constants are different, the band gaps structure should be changed, which can be designed …
We introduce topological phases in Photonic Time-Crystals. Photonic Time-Crystals are materials in which the refractive index varies periodically and abruptly in time. When the refractive index changes abruptly, the light propagating in the material experiences time-refraction and time-reflection, analogous to refraction and reflection in photonic crystals. Interference between time-refracted and time-reflected waves gives rise to Floquet-Bloch states and dispersion bands, which are gapped in the momentum. We show that photonic time-crystals can be in a topologically non-trivial phase, and cal…
We study the transmission properties for the waveguide bends composed by a circular photonic crystal. Two types (Y and U type) of the waveguide bends utilizing the circular photonic crystal are studied. It has been shown, compared with the conventional photonic crystal waveguide bends, transmission properties for these bends can be significantly improved. Over a 6.4% bandwidth, less than 1-dB loss/bend are observed. U bent waveguide, i.e., $180^o$ bend, can be easily realized with low loss using the circular photonic crystal.
We demonstrate a method to locally control the temperature of photonic crystal devices via micron-scale electrical heaters. The method is used to control the resonant frequency of InAs quantum dots strongly coupled to GaAs photonic crystal resonators. This technique enables independent control of large ensembles of photonic devices located on the same chip at tuning speed as high as hundreds of kHz.
Photonic crystal slabs have been widely used in nanophotonics for light confinement, dispersion engineering, nonlinearity enhancement, and other unusual effects arising from their structural periodicity. Sub-micron device sizes and mode volumes are routine for silicon-based photonic crystal slabs, however spectrally they are limited to operate in the near infrared. Here, we show that two single-layer graphene sheets allow silicon photonic crystal slabs with submicron periodicity to operate in the terahertz regime, with an extreme 100x wavelength reduction and excellent out-of-plane confinement…
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。
We present a general approach for coupling a specific mode in a planar photonic crystal (PC) waveguide to a desired free-space mode. We apply this approach to a W1 PC waveguide by introducing small index perturbations to selectively couple a particular transverse mode to an approximately Gaussian, slowly diverging free space mode. This "perturbative photonic crystal waveguide coupler" (PPCWC) enables efficient interconversion between selectable propagating photonic crystal and free space modes with minimal design perturbations.
We show that, taking a two-dimensional photonic-crystal slab system as an example, surprisingly high quality factors (Q) over 10^5 are achievable, even in the absence of a rigorous photonic-band-gap. We find that the density of in-plane Bloch modes can be controlled by creating additional photon feedback from a finite-size photonic-crystal boundary that serves as a low-Q resonator. This mechanism enables significant reduction in the coupling strength between the bound state and the extended Bloch modes by more than a factor of 40.
A method is presented for modelling the optical properties of a photonic crystal structure mounted on a substrate which is thick enough that the light reflected from the back is incoherent with reflections from the front. Transmission and reflection spectra are presented for the cases where the structure is a multilayer planar microcavity and an opal photonic crystal. The contributions from the incoherent reflections can be very large, and in the photonic crystal case, change the positions of the spectral peaks.
Designing the structure of an one-dimensional photonic crystal with a given spectrum of the reflection coefficient
本文提出一种将任意给定反射谱展开为基本光子带隙并求和的一维光子晶体逆向设计方法，并通过实验制备简单反射谱实例验证其可行性。
We present slow-light photonic crystal waveguide designs that provide a $\times$8.6 improvement of the local density of optical states at a fully chiral point over previous designs.
We investigate propagation of light pulses in photonic crystals in the vicinity of the zero-diffraction point. We show that Gaussian pulses due to nonzero width of their spectrum spread weakly in space and time during the propagation. We also find the family of nonspreading pulses, propagating invariantly in the vicinity of the zero diffraction point of photonic crystals.
In this paper, a non-Hermitian two-dimensional photonic crystal flat lens is proposed. The negative refraction of the second band of photonic crystal is utilized to realize super-resolution imaging of the point source. Based on the principles of non-Hermitian systems, a negative imaginary part is introduced into the imaging frequency, in which case the imaging intensity and resolution are improved. The results indicate that the non-Hermitian system provides a new method to improve the imaging performance of the photonic crystal lens.
Photonic components based on structured metallic elements show great potential for device applications where field enhancement and confinement of the radiation on a subwavelength scale is required. In this paper we report a detailed study of a prototypical metallo-dielectric photonic structure, where features well known in the world of dielectric photonic crystals, like band gaps and defect modes, are exported to the metallic counterpart, with interesting applications to infrared science and technology, as for instance in quantum well infrared photodetectors, narrow-band spectral filters, and …
We demonstrate second harmonic generation at telecommunications wavelengths in L3 photonic crystal cavities in (111)-oriented GaAs. The second harmonic power from photonic crystal cavities fabricated in (111)-oriented GaAs is significantly increased compared to those fabricated in conventional (001)-oriented GaAs.
In this paper, we have firstly proposed a new one-dimensional varied-time photonic crystals, i.e., the refractive indices of media $A$ and $B$ are the time functions. We consider the varied-time photonic crystals of refractive indices period variation and calculate the transmissivity and electronic field distribution with and without defect layer, which are different from the conventional photonic crystals, which transmissivity and electronic field distribution are static, but the varied-time photonic crystals transmissivity and electronic field distribution are dynamic. We have obtained some …
Creation of photonic crystal structures with arbitrary spectral features
提出一种构建具有任意预定反射光谱的光子晶体结构的方法，通过算法设计、数值模拟和实验样品验证，实现了光谱响应的精确控制。
We propose a new class of one-dimensional (1D) photonic waveguides: the fractal photonic crystal waveguides (FPCWs). These structures are photonic crystal waveguides (PCWs) etched with fratal distribution of grooves such as Cantor bars. The transmission properties of the FPCWs are investigated and compared with those of the conventional 1D PCWs. It is shown that the FPCW transmission spectrum has self-similarity properties associated with the fractal distribution of grooves. Furthermore, FPCWs exhibit sharp localized transmissions peaks that are approximately equidistant inside the photonic ba…
We study surface states of 1D photonic crystals using a semiclassical coupled wave theory. Both TE and TM modes are treated. We derive analytic approximations that clarify the systematics of the dispersion relations, and the roles of the various parameters defining the crystal.
Bichromatic photonic crystal structures are based on the coexistence of two different periodicities in the dielectric constant profile. They are realized starting from a photonic crystal waveguide and modifying the lattice constant only in the waveguide region. In this work, we numerically investigate the spectral and topological properties of bichromatic structures. Our calculations demonstrate that they provide a photonic analog of the integer quantum Hall state, a well known example of a topological insulator. The nontrivial topology of the bandstructure is illustrated by the formation of s…
We demonstrate high optical quality factors in aluminum nitride (AlN) photonic crystal nanobeam cavities. Suspended AlN photonic crystal nanobeams are fabricated in sputter-deposited AlN-on-insulator substrates using a self-protecting release process. Employing one-dimensional photonic crystal cavities coupled to integrated optical circuits we measure quality factors up to 146,000. By varying the waveguide-cavity coupling gap, extinction ratios in excess of 15 dB are obtained. Our results open the door for integrated photonic bandgap structures made from a low loss, wide-transparency, nonlinea…
Interface states in photonic crystals usually require defects or surface/interface decorations. We show here that one can control interface states in 1D photonic crystals through the engineering of geometrical phase such that interface states can be guaranteed in even or odd, or in all photonic bandgaps. We verify experimentally the designed interface states in 1D multilayered photonic crystals fabricated by electron beam vapor deposition. We also obtain the geometrical phases by measuring the reflection phases at the bandgaps of the PCs and achieve good agreement with the theory. Our approach…
We reported about observation of Dirac points in a helically structured 1D photonic crystals, moreover, both as in the presence of longitudinal magnetic field as its absence. We obtained analytical formulas for Dirac points frequencies and the analytical dispersion relations for wave vectors.
We report a photonic crystal surface emitting laser using monolayer tungsten disulfide as the gain medium. The cavity design utilizes a heterostructure in the photonic crystal lattice to provide lateral confinement for a high quality factor with a compact active region. Room temperature continuous wave lasing is realized after integrating monolayer tungsten disulfide flakes onto the silicon nitride photonic crystal on quartz substrate. Highly directional, near surface normal emission has also been experimentally demonstrated.
Edge states of photonic crystals have attracted much attention for the potential applications such as high transmission waveguide bends, spin dependent splitters and one-way photonic circuits. Here, we theoretically discuss and experimentally observe the deterministic edge states in checkerboard photonic crystals. Due to the self-complementarity of checkerboard photonic crystals, a common band gap is structurally protected between two photonic crystals with different unit cells. Deterministic edge states are found inside the common band gap by exploiting the Zak phase analysis and surface impe…
In this article, we present a numerical study of the optical properties of a metal nanowire interacting with a localized cavity in a two dimensional photonic crystal. The nature of the modes, their wavelength and width are investigated as a function of the particle radius. It is shown in particular that a particle with diameter about the lattice constant presents very narrow resonances corresponding to hybrid photonic-plasmonic modes, where increased lifetime is attributed to the decrease of the radiative losses by interaction with the photonic crystal. These results open interesting applicati…
This paper is withdrawn.
We demonstrate a mesoscopic self-collimation effect in photonic crystal superlattices consisting of a periodic set of all-positive index 2D photonic crystal and homogeneous layers. We develop an electromagnetic theory showing that diffraction-free beams are observed when the curvature of the optical dispersion relation is properly compensated for. This approach allows to combine slow light regime together with self-collimation in photonic crystal superlattices presenting an extremely low filling ratio in air.
Photonic crystal lasers operating at room temperature based on high Q/V nanobeam cavities have been demonstrated. We reported a large spontaneous emission factor (~0.97) by fitting the L-L curve with the rate equations.
An imaging system functioning as a Veselago lens has been proposed based on the novel concept of photonic "hyper-crystal" -- an artificial optical medium synthesizing the properties of hyperbolic materials and photonic crystals. This Veselago lens shows a nearly constant negative refractive index and substantially reduced image aberrations. It can find potential applications in photolithography and hot-spots detection of silicon-based integrated circuits.
We propose a method to directly visualize the photonic band-structure of micron size photonic crystals using wide angle spectroscopy. By extending Fourier Imaging Spectroscopy sensitivity into the infrared range we have obtained accurate measurements of the band-structures along the high-symmetry directions (X-W-K-L-U) of polymeric three-dimensional rod-connected diamond photonic crystals. Our implementation also allows us to record single-wavelength reflectance far field patterns showing a very good agreement with simulations of the same designs. This technique is suitable for the characteriz…
We have measured the photonic bandgap in the transmission of microwaves through a two-dimensional photonic crystal slab. The structure was constructed by cementing acrylic rods in a hexagonal closed-packed array to form rectangular stacks. We find a bandgap centered at approximately 11 GHz, whose depth, width and center frequency vary with the number of layers in the slab, angle of incidence and microwave polarization.
Moiré Photonic Crystals: from Fabric to Magic
研究莫尔光子晶体的宏观与亚波长特性，揭示其独特的慢光模式及零群速特性。
The efficiency of evanescent coupling between a silica optical fiber taper and a silicon photonic crystal waveguide is studied. A high reflectivity mirror on the end of the photonic crystal waveguide is used to recollect, in the backwards propagating fiber mode, the optical power that is initially coupled into the photonic crystal waveguide. An outcoupled power in the backward propagating fiber mode of 88% of the input power is measured, corresponding to a lower bound on the coupler efficiency of 94%.
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