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Metal oxides have long suffered from losses of electronic conductivity and structural durability in the form of three-dimensional nanostructure. Encapsulation with a carbon-based electrocatalyst su...

Single-crystal perovskites with excellent photophysical properties are considered to be ideal materials for optoelectronic devices, such as lasers, light-emitting diodes and photodetectors. However...

Nonlinear optical materials are cornerstones of modern optics including ultrafast lasers, optical computing, and harmonic generation. The nonlinear coefficients of optical materials suffer from limitations in strength and bandwidth. Also, the nonlinear performance is typically monotonous without polarization selectivity, and to date, no natural material has been found to possess nonlinear coefficients with positive or negative signs simultaneously at a specific wavelength, all of which impede practical applications in the specific scenario. Here, we realize broadband large optical nonlinearity accompanied with ultrafast dynamics in a coupled system composed of gold dolmens and an epsilon-near-zero material for dual orthogonal polarizations simultaneously. The system also shows the polarization-selected nonlinearity transition properties, where the sign of the optical nonlinear refractive indexes can be converted via polarization switching. This guarantees active transitions from self-focusing to self-defocusing by polarization rotation without tuning wavelength in practical utilizations. The measured nonlinear refractive index and susceptibility demonstrate more than three orders of magnitude enhancement over a 400-nm-bandwidth compared with the constituents, while maintaining the sub-1 ps time response. The realized enhanced, ultrafast response, and the polarization tunability ensure the designed system a promising platform for the development of integrated ultrafast laser sources, all-optical circuits and quantum chips.

Broadband dispersion free, large and ultrafast nonlinear material platforms comprise the essential foundation for the study of nonlinear optics, integrated optics, intense field optical physics, and quantum optics. Despite substantial research efforts, such material platforms have not been established up to now because of intrinsic contradictions between large nonlinear optical coefficient, broad operating bandwidth, and ultrafast response time. In this work, a broadband dispersion free, large and ultrafast nonlinear material platform based on broadband epsilon-near-zero (ENZ) material is experimentally demonstrated, which is designed through a novel physical mechanism of combining structural dispersion and material dispersion. The broadband ENZ material is constructed of periodically nanostructured indium tin oxide (ITO) films, and the structure is designed with the help of theoretical predictions combined with algorithm optimization. Within the whole broad ENZ wavelength range (from 1300 to 1500 nm), a wavelength-independent and large average nonlinear refractive index of −4.85 × 10−11 cm2/W, which is enlarged by around 20 times than that of an unstructured ITO film at its single ENZ wavelength, and an ultrafast response speed at the scale of Tbit/s are experimentally reached simultaneously. This work not only provides a new approach for constructing nonlinear optical materials but also lays the material foundation for the application of nanophotonics.

A comprehensive understanding of the ultrafast electron dynamics in two-dimensional transition metal dichalcogenides (TMDs) is necessary for their applications in optoelectronic devices. In this wo...

On-chip plasmon-induced transparency (PIT) possessing the unique properties of controlling light propagation states is a promising way to on-chip ultrafast optical connection networks as well as integrated optical processing chips. On-chip PIT has attracted enormous research interests, the latest developments of which have also yield progress in nanophotonics, material science, nonlinear optics, and so on. This review summarizes the realization methods, novel configurations, diversiform materials, and the improved performance indexes. Finally, a brief outlook on the remaining challenges and possible development direction in the pursuit of the application of a practical on-chip photonic processor based on PIT is also afforded.

A series of MoO3/ZrO2 catalysts were prepared by impregnation method, and characterized by X-ray diffraction (XRD), specific surface area (BET) and temperature-programmed desorption of NH3 ...

Phase-change materials (PCMs) are important photonic materials that have the advantages of a rapid and reversible phase change, a great difference in the optical properties between the crystalline and amorphous states, scalability, and nonvolatility. With the constant development in the PCM platform and integration of multiple material platforms, more and more reconfigurable photonic devices and their dynamic regulation have been theoretically proposed and experimentally demonstrated, showing the great potential of PCMs in integrated photonic chips. Here, we review the recent developments in PCMs and discuss their potential for photonic devices. A universal overview of the mechanism of the phase transition and models of PCMs is presented. PCMs have injected new life into on-chip photonic integrated circuits, which generally contain an optical switch, an optical logical gate, and an optical modulator. Photonic neural networks based on PCMs are another interesting application of PCMs. Finally, the future development prospects and problems that need to be solved are discussed. PCMs are likely to have wide applications in future intelligent photonic systems.

We demonstrate a low power all-optical switch in hybrid silicon resonator at room temperature, utilizing exceptionally high nonlinearity in solution integrated perovskite.

We demonstrated a low loss (

The realization of low-energy-consumption lasers based on atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs) is crucial for the development of optical communications, flexible displays, and lasers on the chip level. However, among the as-demonstrated TMDC-based lasers so far, the gain materials are mainly achieved by a mechanical exfoliation approach accompanied by poor reproducibility and controllability. In this work, we report a controllable design for generating large-scale lasing from chemical vapor deposition (CVD)-derived high-quality monolayer MoS2 film. Strong continuous-wave optically driven whispering-gallery-mode lasing is achieved in a wide temperature range from 77 to 400 K. The eminent lasing performances result from the strong spatial confinement of carriers and the enhanced efficiency of spontaneous emission owing to the lensing and screening effects of silica microsphere cavities. These findings not only advance the fundamental understanding of 2D lasing effect...

Two-dimensional van der Waals materials are interesting for fundamental physics exploration and device applications because of their attractive physical properties. Here, we report a strategy to realize photoluminescence (PL) enhancement of two-dimensional transition-metal dichalcogenides (TMDCs) in the visible range using a plasmonic microstructure with patterned gold nanoantennas and a metal–insulator–semiconductor–insulator–metal structure. The PL intensity was enhanced by a factor of two under Y-polarization due to the increased radiative decay rate by the surface plasmon radiation channel in the gold nanoantennas and the decreased nonradiative decay rate by suppressing exciton quenching in the SiO2 isolation layer. The fluorescence lifetime of monolayer tungsten disulfide in this structure was shorter than that of a sample without patterned gold nanoantennas. Tailoring the light–matter interactions between two-dimensional TMDCs and plasmonic nanostructures may provide highly efficient optoelectronic devices such as TMDC-based light emitters.

As Moore's law predicted, field-effect transistors (FETs) have been decreasing in size for several decades. In the process, these devices have suffered considerably from short-channel effects and surface instabilities. Low-dimensional materials, such as 0D quantum dots, 1D nanowires and nanotubes, and 2D nanosheets, would be helpful in the device downscaling process while also enhancing device performance, and have therefore been widely applied in many recently designed FETs. Since the 1990s, more than five million studies related to low-dimensional materials-based FETs have been published. In this article, a universal framework is provided to describe the recent progress in this advanced field and it includes discussions of novel materials, new device configurations and the wide variety of device applications.

Terahertz (THz) metasurfaces composed of Pancharatnam-Berry (PB) meta-atoms have great potential for applications in THz imaging, biological sensing, and optical communication. However, traditional THz PB metasurfaces suffer from inflexible electromagnetic responses and complicated structures. Here, we propose a thermally tunable reflection-type InSb-based THz PB meta-atom, which can not only convert the incident circularly-polarized (CP) wave into cross-polarized components but also adjust the reflection efficiency by increasing the temperature of InSb from 220 K to 360 K. Moreover, various functional devices, including anomalous reflector, reflection-type metalens, and reflection-type OAM beam generators, are investigated with the finite difference time-domain (FDTD) method by using the proposed meta-atom. The working states of these devices can be switched from “ON” to “OFF” at the frequency of 1 THz successfully by changing the temperature of InSb from 220 K to 360 K. This work not only paves a way for the study of tunable multifunctional THz PB devices, but also promotes the practical applications of THz metasurfaces.

Topological photonic nanocavity provides a robust platform for realizing nano-photonic devices and studying light–matter interaction. Here, a topological photonic-plasmonic hybrid nanocavity, assembling a topological photonic crystal (PhC) nanocavity with a plasmonic nano-antenna, is proposed to have an ultra-high figure of merit Q/V of 1.5 × 10 6 ( λ / n ) − 3 , which is two orders higher than that of the bare topological PhC nanocavity. The single-atom cooperativity parameter is improved by over 60 times due to the large enhancement of Q/V, which makes the coupling between light and a single emitter enter a strong coupling region in topological photonic realm for the first time. Meanwhile, strong coupling and weak coupling can be easily switched in the topological hybrid system by tuning the structure dimension of plasmonic nano-antennas. This work provides a robust platform to control coupling phase transition between light and a single emitter, which has great potential in topological lasers, quantum optics and quantum information.

Low-power, ultra-fast all-optical tunable dual Fano resonance was realized in a metamaterial coated with a non-linear nanocomposite layer composed of gold nanoparticle-doped polycrystalline barium ...

Ultracompact chip-integrated all-optical half- and full-adders are realized based on signal-light induced plasmonic-nanocavity-modes shift in a planar plasmonic microstructure covered with a nonlinear nanocomposite layer, which can be directly integrated into plasmonic circuits. Tremendous nonlinear enhancement is obtained for the nanocomposite cover layer, attributed to resonant excitation, slow light effect, as well as field enhancement effect provided by the plasmonic nanocavity. The feature size of the device is 2), which is reduced by two orders of magnitude compared with previous reports. The intensity contrast ratio between two output logic states, “1” and “0,” is larger than 27 dB, which is among the highest values reported to date. Our work is the first to experimentally realize on-chip half- and full-adders based on nonlinear plasmonic nanocavities having an ultrasmall feature size, ultralow threshold power, and high intensity contrast ratio simultaneously. This work not only provides a platform for the study of nonlinear optics, but also paves a way to realize ultrahigh-speed signal computing chips.

A photodetector is a key device to extend the cognition fields of mankind and to enrich information transfer. With the advent of emerging nanomaterials and nanophotonic techniques, new explorations and designs for photodetection have been constantly put forward. Here, we report the asymmetric-light-excitation photoelectric detectors with symmetric electrical contacts working at zero external bias. Unlike conventional photodetectors with symmetric contacts which are usually used as photoconductors or phototransistors showing no photocurrent at zero bias, in this device, the asymmetric-light-excitation structure is designed to ensure that only one Schottky junction between two metallic electrodes and semiconductors is illuminated. In this condition, a device can contribute to a photocurrent without bias. Furthermore, incident light with global illumination will be redistributed by the top Au patterns on devices. The achievement of detectors benefits from the designed redistribution of optical field on specific Schottky barriers within optically active regions and effective carrier collection, producing unidirectional photocurrent for large-scale detection applications. The response mechanisms, including excitations under different polarizations, wavebands, and tilted incidences, were systematically elaborated. Device performances including photocurrent, dynamic response, and detectivity were also carefully measured, demonstrating the possibility for applications in high-speed imaging sensors or integrated optoelectronic systems. The concept of asymmetric-light-excitation photodetectors shows wider availability to other nanomaterials for modern optoelectronics.

On-chip light sources are essential components for integrated photonic circuits and quantum information processing chips. High directionality, high collection efficiency, and ultrasmall feature size are the most significant features for a light source in the wavelength range for optical communication, around 1550 nm. The authors use nanomanipulation to create an ultrasmall, unidirectional on-chip light source based on PbS quantum dots and an epsilon-near-zero (ENZ) material. This work not only shows the way to integrated photonic devices based on ENZ materials, but also provides an advanced method for the precise assembly of composite functional nanostructures.

Optical cavity polaritons, originated from strong coupling between the excitons in materials and photons in the confined cavities field, have recently emerged as their applications in the high-speed lowpower polaritons devices, low-threshold lasing and so on. However, the traditional exciton polaritons based on metal plasmonic structures or Fabry-Perot cavities suffer from the disadvantages of large intrinsic losses or hard to integrate and nanofabricate. This greatly limits the applications of exciton poalritons. Thus, here we implement a compact low-loss dielectric photonic — organic nanostructure by placing a 2-nm-thick PVA doped with TDBC film on top of a planar Si asymmetric nanogratings to reveal the exciton polaritons modes. We find a distinct anti-crossing dispersion behavior appears with a 117.16 meV Rabi splitting when varying the period of Si nanogratings. Polaritons dispersion and mode anti-crossing behaviors are also observed when considering the independence of the height of Si, width of Si nanowire B, and distance between the two Si nanowires in one period. This work offers an opportunity to realize low-loss novel polaritons applications.

We use interference coupling of plasmonic nanocavity and dielectric photonic crystal nanocavity, and unidirectional coupling of bright and dark metaatom modes, to achieve a giant slow light effect.

Valley photonic crystals can enable nontrivial topology locked to the valley index. Since time-reversal symmetry is preserved, no external magnetic field has to be applied. Therefore, the valley topological insulators can be easily used to construct photonic devices. Here, a reconfigurable valley photonic crystal is proposed, where the inversion symmetry is broken by constructing the unit cell with two different materials. Also, since one of the materials is electro-optic material barium titanate, by simply changing the applied voltage, not only the band-gap frequency will shift, but the topological phase transition can also happen. This is highly beneficial to the design and optimization of integrated photonic devices because a balance between the flexibility of devices and the robustness of topological properties is realized successfully. Moreover, a two-port optical switch as an example of the possible applications is proposed.

National Key Research and Development Program of China [2018YFB2200403, 2018YFA0704404]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [61775003, 11734001, 91950204, 11527901, 11704017, 91850117, 11654003]; Beijing Municipal Science & Technology CommissionBeijing Municipal Science & Technology Commission [Z191100007219001]; Natural Science Foundation of Beijing MunicipalityBeijing Natural Science Foundation [Z180015]; Beijing Institute of Technology Research Fund Program for Young Scholars

Chip-integrated multiple electromagnetically induced transparencies are realized using a photon–plasmon composite nanocavity (composed of a single photonic crystal nanocavity coupled with a single plasmonic nanocavity), i.e., comprehensively utilizing the superiorities of photonics as well as plasmonics. The destructively interferential coupling of one broad-band plasmonic nanocavity mode with two narrow-band silicon photonic crystal nanocavity modes generates two electromagnetically induced transparency windows. The two transparency windows simultaneously have a narrow line width of 15 nm, a high transmission contrast of 70%, and a strong slow light effect. A large group refractive index of more than 400 is obtained at the transparency window center, indicating a 10-fold increase in comparison with earlier results. The photon–plasmon composite nanocavity has a feature size of only 2 μm. The transparency window shifts 30 nm for the photon–plasmon composite nanocavity covered with a monolayer of graphene e...

Ultracompact chip-integrated all-optical diode is realized experimentally in a plasmonic microstructure, consisting of a plasmonic waveguide side-coupled two asymmetric plasmonic composite nanocavities covered with a multicomponent nanocomposite layer, formed directly in a plasmonic circuit. Extremely large optical nonlinearity enhancement is obtained for the multicomponent nanocomposite cover layer, originating from resonant excitation, slow-light effect, and field enhancement effect. Nonreciprocal transmission was achieved based on the difference in the shift magnitude of the transparency window centers of two asymmetric plasmonic nanocavities induced by the signal light, itself, for the forward and backward propagation cases. An ultralow threshold incident light power of 145 μW (corresponding to a threshold intensity of 570 kW/cm2) is realized, which is reduced by seven orders of magnitude compared with previous reports. An ultrasmall feature size of 2 μm and a transmission contrast ratio of 15 dB are obtained simultaneously.

Active electric control of highly efficient third harmonic generation was realized in an ultrathin nonlinear metasurface by using a nanocomposite consisting of gold nanoparticles dispersed in polycrystalline strontium titanate as the electro-optic material. Owing to the nonlinearity enhancement associated with the slow light effect, quantum confinement effect, and field-reinforcement, a high conversion efficiency of 3 × 10 −5 was obtained, which is two orders of magnitude larger than previously reported efficiencies at comparable pump intensities. A modulation of 12% in the intensity of the third harmonic generation and a 30-nm shift in the transparency window center were achieved by varying the applied voltage from −30 V to zero. Our results pave the way toward the realization of multi-functional integrated photonic devices and chips based on metasurfaces.

Exciton polaritons, quasiparticles that strongly integrate transition metal dichalcogenides with large exciton binding energies and optical fields, exhibit unique properties due to their strong excitonic nonlinearity. However, intrinsic absorption losses pose a fundamental obstacle to all-optical tunability in exciton-polaritons due to the relatively broad resonance spectra. Therefore, it is necessary to determine structural configurations based on transition metal dichalcogenides to enhance the field distribution. Herein, the experimental details of a narrow trapped-mode based on asymmetric WS2 localized exciton-polaritons dual gratings are presented. The transmission value at the trapped mode wavelength can be tuned from 0.844 to 0.53 for an excitation power of 14.93 MWcm−2 with a pump wavelength of 366 nm. This is attributed to the narrow trapped-mode resonance and strong field enhancement in the asymmetric gratings. A relaxation time of approximately 35 ps is obtained, which is determined by the exciton lifetime of the WS2 flake. This work provides a foundation for the application of exciton-polaritons in all-optical devices.

Subwavelength periodic confinement can collectively and selectively enhance local light intensity and enable control over the photo-induced phase transformations at the nanometer scale. Standard nanofabrication process can result in geometrical and compositional inhomogeneities in optical phase change materials, especially chalcogenides, as those materials exhibit poor chemical and thermal stability. Here we demonstrate the self-assembled planar chalcogenide nanostructured array with resonance enhanced light emission to create an all-dielectric optical metasurface, by taking advantage of the fluid properties associated with solution processed films. A patterned silicon membrane serves as a template for shaping the chalcogenide metasurface structure. Solution-processed arsenic sulfide metasurface structures are self-assembled in the suspended 250 nm silicon membrane templates. The periodic nanostructure dramatically manifests the local light-matter interaction such as absorption of incident photons, Raman emission, and photoluminescence. Also, the thermal distribution is modified by the boundaries and thus the photo-thermal crystallization process, leading to the formation of anisotropic nano-emitters within the field enhancement area. This hybrid structure shows wavelength selective anisotropic photoluminescence, which is a characteristic behavior of the collective response of the resonant guided modes in a periodic nanostructure. The resonance enhanced Purcell effect could manifest the quantum efficiency of localized light emission.

The topological edge states of the coupled-resonator optical waveguide (CROW) system have been widely researched. Without breaking time-reversal symmetry nor needing to construct complicated optical modes as pseudospins, the CROW system offers characteristics that are effective for exploration of photonic topological effects and has potential for applications in nanodevices. We extend the previous method by using specific coupling conditions to calculate the system's actual band structure, thereby providing a new perspective of this system. Two types of topological properties, one with and the other without an artificial magnetic field, are identified based on the band diagrams. Fractal spectra including the Hofstadter butterfly spectrum are obtained, revealing the abundant physics associated with the CROW system. By connecting the band diagrams with the corresponding structural parameters, we propose a triangular lattice array with reduced losses at the corners and propose a scheme with the potential for use as a reconfigurable multipath platform.

In this contribution, we report a reduced graphene oxide (rGO)-modified nitrogen-doped carbon xerogel, which could be easily prepared by pyrolysis of melamine-formaldehyde (MF) resins that are polymerized hydrothermally in an aqueous GO dispersion. Scanning electron microscopy, transmission electron microscopy, Fourier-transformed infrared spectrometry, and nitrogen adsorption-desorption method were employed to reveal the morphologies and structures of the prepared carbon xerogel. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge were used to investigate the electrochemical properties. The results showed that the charge transfer barrier of the mesoporous nitrogen-doped carbon xerogel was decreased evidently, owing to the modification of a layer of rGO on its wall, and the xerogel demonstrated a capacitance of as high as 205 F g−1 at the current of 1 A g−1.

Surface plasmon polariton, a kind of surface electromagnetic wave propagating along the interface between metals and dielectrics, provides an excellent platform for the realization of integrated photonic devices due to its unique properties of confining light into subwavelength scales. Our recent research progresses of nanoscale integrated photonic devices based on surface plasmon polaritons, including all-optical switches, all-optical logic discriminator, and all-optical routers, are introduced in detail.

Ultrafast all-optical switching, possessing the unique function of light controlling light, is an essential component of on-chip ultrafast optical connection networks as well as integrated logic computing chips. Ultrafast all-optical switching has attracted enormous research interests, the latest great developments of which have also yield progress in nanophotonics, integrated optics, nonlinear optics, material science, and optical communications, and so on. This review summarizes the fundamental realization principles, novel configurations, fancy materials, improved performance indexes, and ameliorated trigger method (transitioning from a traditional impractical free-space-vertical trigger to a more practical on-chip trigger) of ultrafast all-optical switching. Not only a systematic discussion of the current state-of-the art is provided, but also a brief outlook on the remaining challenges in the pursuit of the application of a practical on-chip ultrafast all-optical switching is also afforded.

The nanoscale wavelength and polarization router, which can simultaneously separate wavelength and polarization modes, is an essential component of on-chip nanophotonic devices. Here, an on-chip wavelength and polarization router is realized experimentally based on a three-layer hybrid waveguide of Au−SiO2−LiNbO3 etched with asymmetric nano-cavities. The central area size of the device is only 1.60×1.96 μm2. A broad operation band covers from 500 nm to 1150 nm with low cross talk of under 10 dB. The monolithic-LiNbO3is introduced for the first time, to the best of our knowledge, to on-chip multichannel wavelength and polarization routers. This work plays a key role for dense chip integration, visible light displays, and communications, and can inspire LiNbO3-based nanophotonic devices.

Integrated nanoscale photonic devices have wide applications ranging from optical interconnects and optical computing to optical communications. Wavelength demultiplexer is an essential on-chip optical component which can separate the incident wavelength into different channels; however, the experimental progress is very limited. Here, using a multi-component nano-cavity design, we realize an ultracompact, broadband and high-contrast wavelength demultiplexer, with 2.3 μm feature size, 200 nm operation bandwidth (from 780 nm to 980 nm) and a contrast ratio up to 13.7 dB. The physical mechanism is based on the strong modulation of the surface plasmon polaritons induced by the multi-component nano-cavities and it can be generalized to other nanoscale photonic devices. This provides a strategy for constructing on-chip photon routers and also has applications for chip-integrated optical filter and optical logic gates.

We realized all-optical tunable optical devices based on Fano Resonance in multilayer transition-metal-oxide metamaterials. Combined the plasmonic resonance and slow light effect, an enhanced third-harmonic generation (THG) was realized on strontium titanate composite material.

We report a picosecond and low-power all-optical switch with multiple operating wavelengths in integrated photonic circuits, on-chip-triggered by a control light. The sample configuration combines the advantages of plasmonics and photonics, i.e. plasmonic nanostructures used as core units interconnected by ultralow-loss dielectric slot waveguides. A large nonlinearity enhancement is obtained based on resonant excitation, local field effect, and field enhancement effect, while fast response is maintained by intermolecular energy transfer. A fast response of 63 ps and ultralow control light intensity of 450 kW/cm2 are achieved.