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Tuning the thermal properties of materials is considered to be of crucial significance for improving the performance of electronic devices. Along these lines, the development of van der Waals (vdW) heterostructures becomes an effective solution to affect the thermal transport mechanisms. However, vdW interactions usually block phonon transport, which leads to a reduction in thermal conductivity. In this work, we experimentally demonstrate a large enhancement in the thermal conductivity of a vdW heterostructure composed of few-layer hexagonal boron nitride (h-BN) and reduced graphene oxide (RGO). By controlling the reduction temperature of RGO and changing the thickness of h-BN, the thermal conductivity of the RGO is increased by nearly 18 times, namely, from 91 to 1685 W m

The PL emission and carrier relaxation of CuInP2S6 vary greatly with temperature under phase transition, while the two-photon absorption changes slightly with temperature.

Rhenium diselenide (ReSe2) has gathered much attention due to its low symmetry of lattice structure, which makes it possess in-plane anisotropic optical, electrical as well as excitonic properties and further enables ReSe2 have an important application in optoelectronic devices. Here, we report the thickness-dependent exciton relaxation dynamics of mechanically exfoliated few-layer ReSe2 flakes by using time-resolved pump–probe transient transmission spectroscopies. The results reveal two thickness-dependent relaxation processes of the excitons. The fast one correlates with the exciton formation (i.e., the conversion of hot carriers to excitons), while the slow one is attributed to the exciton recombination dominated by defect-assisted exciton trapping besides photon emission channel. The decrease of scattering probability caused by defects leads to the increase of fast lifetime with thickness, and the increase of slow lifetime with thickness is related to the trap-mediated exciton depopulation induced by surface defects. Polarization dependent transient spectroscopy indicates the isotropic exciton dynamics in the 2D plane. These results are insightful for better understanding of excitonic dynamics of ReSe2 materials and its application in future optoelectronic and electronic devices.

Generative adversarial networks are an emerging technique with wide applications in machine learning, which have achieved dramatic success in a number of challenging tasks including image and video generation. When equipped with quantum processors, their quantum counterparts—called quantum generative adversarial networks (QGANs)—may even exhibit exponential advantages in certain machine learning applications. Here, we report an experimental implementation of a QGAN using a programmable superconducting processor, in which both the generator and the discriminator are parameterized via layers of single- and two-qubit quantum gates. The programmed QGAN runs automatically several rounds of adversarial learning with quantum gradients to achieve a Nash equilibrium point, where the generator can replicate data samples that mimic the ones from the training set. Our implementation is promising to scale up to noisy intermediate-scale quantum devices, thus paving the way for experimental explorations of quantum advantages in practical applications with near-term quantum technologies.

Highly stable nanopores with precise size and film thickness are essential for ultrasensitive molecular biosensors and efficient ion filters. However, the stability of both solid-state nanopores and biological nanopores is of a few hours. Even for two-dimensional (2D) materials with excellent properties, it is very difficult to prepare nanopores with stability for more than 1 day. Here, in mechanically exfoliated 2D materials with excellent quality, highly stable nanopores have been fabricated. Through the manual control of defect density and laser spot irradiation, the breakdown process is more controllable. The nanopore diameter can be precisely adjusted from 1 to 10 nm. The 2 nm thick graphene nanopore (with a diameter of 2 nm) maintains good consistency in conductivity during the 1-month immersion in KCl (1 M) solution. The pore size changes less than 0.7% per day. We found that 2D material nanopores can produce a strong rectification ratio (∼50) due to the morphology undulation. In addition, our devices can recognize modified 5 nm Au nanoparticles, showing great potential for single-molecule detection. This work can guide the development of high-quality ion rectifier devices and biosensors based on 2D material nanopores.

Recently, palladium diselenide (PdSe

Although abundant research on the anisotropy of van der Waals (vdW) materials has been published, we undertake an in-depth study of their optical properties as they have an important guiding role for light control in two-dimensional (2D) nanospace. As an example, we study the reflectance of few-layered black phosphorus (BP) in the total internal reflection (TIR) mode in detail. We demonstrate that its optical anisotropy can be changed on a large scale by varying the incident angles, polarization states, and the in-plane rotation angles of the BP samples. Theoretical analysis indicates that the phenomena observed are common to all the atom-thick biaxial crystals, so these conclusions can be widely applied to other anisotropic 2D materials. This research furthers the current understanding of the properties of BP more comprehensively, and provides guidance for developing new optoelectronic applications, especially when BP and other atom-thick biaxial crystals are integrated with TIR devices. Keywords: Black phosphorus, Optical anisotropy, Total internal reflection, Biaxial crystal

Scatterings and transport in Weyl semimetals have caught growing attention in condensed matter physics, with observables including chiral zero modes and the associated magnetoresistance and chiral magnetic effects. Measurement of electrical conductance is usually performed in these studies, which, however, cannot resolve the momentum of electrons, preventing direct observation of the phase singularities in scattering matrix associated with Weyl point. Here we experimentally demonstrate a helical phase distribution in the angle (momentum) resolved scattering matrix of electromagnetic waves in a photonic Weyl metamaterial. It further leads to spiraling Fermi arcs in an air gap sandwiched between a Weyl metamaterial and a metal plate. Benefiting from the alignment-free feature of angular vortical reflection, our findings establish a new platform in manipulating optical angular momenta with photonic Weyl systems., Comment: 14 pages, 3 figures

Twisted bilayer graphene (TBG), which has drawn much attention in recent years, arises from van der Waals materials gathering each component together via van der Waals force. It is composed of two sheets of graphene rotated relatively to each other. Moiré potential, resulting from misorientation between layers, plays an essential role in determining the band structure of TBG, which directly relies on the twist angle. Once the twist angle approaches a certain critical value, flat bands will show up, indicating the suppression of kinetic energy, which significantly enhances the importance of Coulomb interaction between electrons. As a result, correlated states like correlated insulators emerge from TBG. Surprisingly, superconductivity in TBG is also reported in many experiments, which drags researchers into thinking about the underlying mechanism. Recently, the interest in the atomic reconstruction of TBG at small twist angles comes up and reinforces further understandings of properties of TBG. In addition, twisted multilayer graphene receives more and more attention, as they could likely outperform TBG although they are more difficult to handle experimentally. In this review, we mainly introduce theoretical and experimental progress on TBG. Besides the basic knowledge of TBG, we emphasize the essential role of atomic reconstruction in both experimental and theoretical investigations. The consideration of atomic reconstruction in small-twist situations can provide us with another aspect to have an insight into physical mechanism in TBG. In addition, we cover the recent hot topic, twisted multilayer graphene. While the bilayer situation can be relatively easy to resolve, multilayer situations can be really complicated, which could foster more unique and novel properties. Therefore, in the end of the review, we look forward to future development of twisted multilayer graphene.

Two-dimensional (2D) bipolar junction transistors (BJTs) with van der Waals heterostructures play an important role in the development of future nanoelectronics. Herein, a convenient method is introduced for fabricating a symmetric bipolar junction transistor (SBJT), constructed from black phosphorus and MoS

The ultrafast nonlinear optical properties of bulk TlGaS

It has been a great challenge to achieve the direct light manipulation of matter on a bulk scale. In this work the direct light propulsion of matter is observed on a macroscopic scale using a bulk graphene-based material. The unique structure and properties of graphene, and the novel morphology of the bulk three-dimensional linked graphene material make it capable not only of absorbing light at various wavelengths but also of emitting energetic electrons efficiently enough to drive the bulk material, following Newtonian mechanics. Thus, the unique photonic and electronic properties of individual graphene sheets are manifested in the response of the bulk state. These results offer an exciting opportunity to bring about bulkscale light manipulation with the potential to realize long-sought applications in areas such as the solar sail and space transportation driven directly by sunlight.

Large area monolayer of self-assembled polystyrene sphere (PS) arrays were formed by an interface self-assembly method and the gap of PS was adjusted by O2 plasma treatment (OPT). After different duration of OPT, the spacing between the PSs varied from 5 to 88 nm. Then, 20 nm Au film was deposited on the PS arrays by electron beam deposition. The absorption peaks of Au-coated PS array red-shifted obviously by changing the gap of PS. The new absorption peaks emerged when the gap of the PS decreased to about 20 nm. The surface plasmon resonance (SPR) was employed to explain the absorption proportion of this Au-PS structure. These micro-nano structures exhibit tunable SPR bands, which may be useful to the applications in some research fields, such as biosensing, single molecule detection, and novel optoelectronic devices.

Nanosphere lithography is an efficient way to fabricate metallic nanostructures with large area. This paper presents the fabrication of metallic hexagonal nano-pyramid arrays by two dimensional nanospheres lithography assisted with O2 plasma treatment. By O2 plasma treatment, the gap and diameter of nanospheres can be modulated. After electron beam deposition, we can fabricate similar nanostructures with different pyramid gap distances. This method may be an easy way to modulate the geometric parameters of nanostructures.

We fabricated inclined Au nanocup arrays by using the nanosphere lithography method combined with dichloromethane etching and investigated their optical properties. The transmittance spectra of these Au nanocup arrays under different polarizations and incident angles were detected and discussed. Surface plasmon resonance was employed to explain the peaks in the spectra. These inclined Au nanocup arrays may be useful for the potential applications in plasmonic devices.

The transmitted and reflected Z-scan characteristics for light-tunneling heterostructures composed of one-dimensional photonic bandgap material and metallic film are theoretically investigated. An apparent Z-scan signal will appear around the light-tunneling even if the incident peak intensity is very low. Both of the transmitted and reflected Z-scan signals from left incidence are much larger than those from right incidence, demonstrating the nonreciprocal for two incident directions. The variation of the reflected Z-scan curve shape is opposite to that of transmitted Z-scan curve shape as light wavelength increases. Moreover, the reflected Z-scan signals from left incidence will show a very sharp peak around the light-tunneling.

Structured subwavelength apertures have been studied widely to enhance the transmission or obtain super resolution, such as bull’s eye hole, H-shaped aperture, and bowtie aperture. In this letter, we present another structured aperture with two gaps inside, which can also lead to near-field enhancement. And the resonance wavelength can be tuned by the geometric parameters of the gaps. The enhancement of this gap-aperture depends strongly on the polarization of the incident wave. Only the polarization perpendicular to the connecting line of the two gaps can realize the enhancement. We attribute the near-field enhancement of this structured aperture to the resonance excitation of the localized surface plasmon. We combine the tooth-aperture and our gap-aperture together and this special aperture can achieve stronger enhancement and super resolution simultaneously.

A wide-angle, split-step finite-difference method with the classical local one-dimensional scheme is presented to analyze the three-dimensional scalar wave equation. Its essence is to convert the three-dimensional scalar wave equation into two two-dimensional equations that can be solved without using slowly varying envelope or one-way propagation approximations. To validate the effectiveness, numerical results for the Gaussian beam propagation in vacuum and the eigen-mode propagation in tilted step-index channel waveguide are compared with other beam propagation algorithms. Results show that the method has high accuracy and numerical efficiency compared with other known split-step methods. The perfectly matched layer boundary condition can be implemented easily.

Enhanced transmission through sub-wavelength hole arrays and a single sub-wavelength aperture with periodic corrugations surrounded have been investigated extensively. We report the similar phenomenon through a funnel-type aperture with a sub-wavelength outlet in a thick silver film, which was obtained numerically by using finite-difference time-domain method. Properties of the transmission spectrum can be modulated by geometric parameters of the funnel-type aperture. With periodic grooves or dielectric gratings on the output surface of the structure, beaming light emission can be obtained.

To assess the quality of life (QOL) of advanced schistosomiasis patients, and understand its influencing factors.A questionnaire survey was carried out by using WHOQOL-BREF, and the information of demography, family, illness, health status, and health service was collected.Among the 217 advanced patients, the average age was (75.33 ± 6.94) years, the ratio of male to female was 2:5, 89.86% of them were farmers, 75.58% were illiterate or semi-illiterate, and 88.94% belonged to the splenomegaly type. Totally 61.29% of the cases had the scores over average for the overall QOL, but the scores for the health and well-being were lower. There were a significant difference among the average scores of different domains of QOL (χ2 = 23.46, P0.01). Both the year of being diagnosed and clinical classification was not associated with the scores of QOL. Regularly taking physical activities was significantly associated with each of all the 4 domains. The factors such as onset of acute disease in 2 weeks, taking therapeutic pills daily, marital status, age, etc. impacted the specific domains of QOL. The overall QOL and the 4 domains of the patients were at medium level; meanwhile, the score of physiological domain was lower than the scores of the other 3 domains.The QOL(s) of advanced schistosomiasis patients in Qingpu District are relatively good. It is important to provide effective community health services and encourage the patients to take part in tempered sports or physical activities in order to keep their normal activities of daily living.

Graphene is an emerging class of two-dimensional (2D) material with unique electrical properties and a wide range of potential practical applications. In addition, graphene hybrid structures combined with other 2D materials, metal microstructures, silicon photonic crystal cavities, and waveguides have more extensive applications in van der Waals heterostructures, hybrid graphene plasmonics, hybrid optoelectronic devices, and optical modulators. Based on well-developed transfer methods, graphene grown by chemical vapor deposition (CVD) is currently used in most of the graphene hybrid applications. Although mechanical exfoliation of highly oriented pyrolytic graphite provides the highest-quality graphene, the transfer of the desired microcleaving graphene (MG) to the structure at a specific position is a critical challenge, that limits the combination of MG with other structures. Herein, we report a new technique for the selective transfer of MG patterns and devices onto chosen targets using a bilayer-polymer structure and femtosecond laser microfabrication. This selective transfer technique, which exactly transfers the patterned graphene onto a chosen target, leaving the other flakes on the original substrate, provides an efficient route for the fabrication of MG-based microdevices. This method will facilitate the preparation of van der Waals heterostructures and enable the optimization of the performance of graphene hybrid devices., 22 pages, 5 figures,Letter

To understand the survival of imported Oncomelania snails in new environments with different densities in waterway net region, Qingpu District, Shanghai.The snails collected from Guichi, Anhui Province were put into the ponds of 4 square meters and each had 25, 50, 100, 200, 400 and 800 pairs of snails, respectively. During the next 2 years, the temperature, humidity, the activities of snails and their second birth snails were investigated each day. All the data were analyzed statistically.The highest number of snails appeared from May to June on the surface of soils in different densities. The average numbers of snails were 2.0%-12.7% of whole put in snails, and the numbers of offspring were less than 2% of the whole put in snails.The survival and reproduction of artificially imported Oncomelania snails from Guichi, Anhui Province is not good in Qingpu District, Shanghai.

A metal-insulator-metal (MIM) waveguide can support two plasmonic modes. Efficient conversion between the two modes can be achieved by reshaping of both phase and power density distributions of the guided mode. The converters are designed with the assistance of transformation optics. We propose two practical configurations for mode conversion, which only consist of homogeneous materials yielded from linear coordinate transformations. The functionalities of the converters are demonstrated by full wave simulations. Without consideration of transmission loss, conversion efficiency of as high as 95% can be realized.

To observe the survival and reproduction of exotic imported Oncomelania snails in water network regions.During a period between May 22, 2008 and August 7, 2009, a study pilot was established in a historical snail habitat in Qingpu District of Shanghai City. A total of 12 soil samples were collected from Qingpu, Jinshan and Songjiang districts and placed in the study area. Active marked adults snails without infections (with a female/male ratio of 1) were placed on soil surface, and the activity, survival and reproduction of snails on soil surface were observed. The temperature during the period of the study was recorded.During the experiment period, the highest temperature was 39 degrees C, the lowest was -3 degrees C, and the average was 20 degrees C. The activity of snails reduced significantly on the soil surface at high temperature in summer and low temperature in winter. There were 91 old snails (5.2%) that moved on soil surface in March and 73 (12.2% ) in June, 2009. A total of 26 and 59 offspring snails were found respectively in April and June, 2009, with average density of 2.17 snails/m2 (26/12) and 4.92 snails/m2 (59/12) respectively.The exotic imported snails can survive and reproduce in water network regions. Further monitoring should be strengthened on the imported snails in these regions.

The transmission from a single subwavelength slit in a metal film with periodic dielectric bars on its surfaces has been analyzed numerically by the finite-difference time-domain method. Results show that the role of the periodic dielectric bars is just the same as that of the periodic grooves directly on the surfaces. With the modulations of dielectric bars on the input and output surfaces of the metal film, light transmission through the subwavelength slit is enhanced extraordinarily and confined to directional emission. The CDEW model is employed to explain the mechanism of the transmission enhancement and directional emission caused by the periodic dielectric bars.

The light transmission through a single subwavelength aperture surrounded by periodic grooves in layered films consisting of Ag and transparent dielectric is analyzed numerically by finite difference time domain (FDTD) method. Results show that the transmission through the aperture in the composite films is strongly enhanced by the modulation of grooves on the transparent dielectric. Two models are employed to explain the mechanisms of transmission enhancement.

The cold-water and boiled-water soaked scrophularia soups have been prepared. The emission and excitation spectra of each scrophularia soup under different conditions have been measured at room temperature. The pH values of the different scrophularia soups have been also detected. There are obvious differences between the cold-water soaked scrophularia soup and the boiled-water soaked scrophularia. For both soups the emission wavelength increases with the wavelength of the excitation, but the peaks of the emission spectra for cold-water and boiled-water soaked scrophularia soup are different, which are 441 and 532 nm, respectively. Excitation spectrum has double peaks in the cold-water soaked scrophularia soup while only one peak with longer wavelength in the boiled-water soaked one. The pH value changes from 5.5 to 4.1. According to the organic admixture fluorescence mechanism we analyzed the reasons of the experimental results. Through heating, the interaction in different fluorescence molecular and the energy transfer process in the same fluorescence molecular become more active, and the conjugate structures and the generation of hydrogen bonds, increase. The fluorescence measurement is of value for the scrophularia pharmacology analysis and provides an analytical method for the quality identification of scrophularia soup.

In the present paper, the properties of Cu(In(1-x) Ga(x)) Se2 (CIGS) thin film absorber materials for the solar cells obtained by selenization of the precursors with In-rich or CuGa-rich surface layers were studied by XRD, SEM and Raman spectra. The photovoltaic devices based on the absorbers were measured and analyzed by illuminated J-V curve subsequently. The performance of the device constructed by the absorbers obtained by selenization of the precursors with CuGa-rich surface layer was improved greatly compared to that with In-rich surface layer. Through Raman spectra measurement, it was found that the Raman peak of the A1 mode was shifted for the CuGa-rich one, which is verified that the band gap of the surface layers was elevated. Moreover the value of increased Ga contents within the surface region of films were calculated by the relation between the Raman shifts and the Ga contents. As a result, the devices based on the thin films with the elevated surface energy band by selenizing the precursors with the CuGa-rich surface layer improved further the V(oc) and FF by about 74 mV and 8% respectively compared to that of corresponding to the one with In-rich surface layers, so that the conversion efficiency of the photovoltaic devices based on these thin films with CuGa-rich surface layer was improved by up to 9.4%. Meanwhile Raman scattering spectroscopy has proven to be a very powerful and useful technique for the surface analysis of such thin film solar cell semiconducuor materials.

Noise sources of the CCD as the photoelectric detection device in an optical multichannel analyzer (OMA) were analyzed, and noise suppression methods were discussed. A high sensitivity OMA was developed successfully on the basis of the noise suppression techniques, and the 7th spectral lines of Balmer series of hydrogen and deuterium were resolved clearly by the OMA. Its sensitivity was enhanced by one order of magnitude, compared with those reported in the literatures. This OMA also showed high resolution, high precision and good reliability in the authors' experiments.

The CCD experimental setup and the CCD image analysis system that were developed by using C Language were presented, and the spatially resolved diffusion reflectance and transmittance of porcine muscle and fat were determined by using CCD experimental setup. The experimental results were compared with those of Monte Carlo simulations and those of the two models based on diffusion theory, and we found good agreement between theory and experiment for the range from the beam center to 12 mm. It i s shown that the CCD experimental setup and the CCD image analysis system can be used to measure the spatially resolved diffusion reflectance and transmittance of biological tissues, and this work offers the experimental bases for noninvasive and fast measurement of optical parameters of biological tissues.

In this paper, gain and noise characteristics of gain-clamped Fabry-Perot lasing erbium-doped fiber amplifier(EDFA) is investigated in detail when reflective wavelength and reflectivity of the fiber Bragg gratings (FBG) areselected different values. The relationships between gain and noise performance of the gain-clamped EDFA and theselection ofFBG parameters such as reflectivity and reflective wavelength are investigated and analyzed. It is found vianumerical simulation that the selection of FBG parameters has important influence on the performance of the EDFA.The results obtained in this paper can provide significant datum and reference for optimizing and improving the performance of all-optical gain-clamped EDFA. Key words: EJJFA; WDM; all-optical gain clamp; Fabry-Perot cavity 1. Introduction Gain-clamped fiber amplifier is indispensable to overcome the gain fluctuations as the requirements in applications of wavelength-division multiplexing communication system. Generally, there are two main methods torealize gain clamping ofEDFA: electrical gain control 41or all-optical gain control5'21. In the former method, drivingcurrent of pumping laser is modulated in real time according to the feedback signal ofthe output power change detectedby controlling circuit to maintain the constant power level. Its main drawback is that many additional electrical devicesare needed and output signals are obtained with high electrical delay. In the latter method, loop or linear lasing cavity isformed by optical components such as fiber grating, variable attenuators and circulators to constitute stable lasing inamplifier, by which the gain fluctuation of EDFA is under control. This scheme has advantages of real time gainclamped and all-optical integration. The gain clamp in an Erbium-doped fiber amplifier (EDFA) achieved by aFabry-Perot lasing with fiber Bragg reflectors has the advantages of having no additional signal loss, lower cost andsimpler configuration comparing with all-optical gain-clamped EDFA obtained by a fiber-ring lasing cavity. In thispaper, The relationships between gain and noise performance of the gain-clamped EDFA and the selection of FBGparameters such as reflectivity and reflective wavelength are investigated and analyzed in detail. It is found vianumerical simulation that the selection of FBG parameters has important influence on the performance of the EDFA.The results obtained in this paper can provide significant datum and reference for optimizing and improving the

We theoretically study the plasmonic modes in metal-multi-insulator-metal (MMIM) waveguides. Two types of symmetric MMIM structures consisting of three insulators are investigated thoroughly. The effective refractive index, energy confinement, propagation length, and figure of merit are given in terms of geometric parameters. Due to the step index modulation, these properties of MMIM structures differ from the metal-insulator-metal (MIM) structure. Compared with the corresponding MIM structures, MMIM structures can possess either better energy confinement or larger propagation length, which depends on the geometric parameters and the index distribution. Propagation length of up to 10(3) µm and a figure of merit of up to 10(4) are observed for MMIM structure with core thickness of several hundred nanometers.