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In this work, we theoretically and experimentally demonstrate that effective trapping, guiding, and manipulation of sound waves can be realized in spoof-fluid-spoof acoustic waveguides with gradient index modulation. Empowered by the abundant mode evolution physics between propagation waves and spoof acoustic surface waves in the gradient waveguide structure, various functional sound propagation phenomena, including broadband transmission, broadband reflection, Fabry–Pérot resonances, and Fano resonances, are unveiled. The underlying principle stems from the interplay of various mechanisms composed of gradient mode conversion, high-order mode resonances, and symmetry-protected bound states in the continuum. These effects can be effectively modulated through the manipulation of the fluid gap and doped defects within the waveguide structure. Our findings can offer possibilities for manipulating sound waves in a versatile manner and holding significant potential for various acoustic applications such as sensing, filtering, insulation, and wavefront engineering. [ABSTRACT FROM AUTHOR]

An acoustic metagrating (MG) constructed with an inverse-design scheme can be used to realize anomalous reflection, but its efficiency is limited. In this work, we find that the evanescent guided modes are an important component of achieving perfect retroreflection in an MG. Considering the evanescent first-order guided mode, we derive an alternative inverse-design condition to produce perfect retroreflection and improved performance in the MG parameter space compared with the traditional method. We further investigate the corresponding contribution ratios of the guided modes to perfect retroreflection and find an orthogonal relationship between the contribution ratios of odd and even guided modes. These findings are confirmed using analytical calculations and numerical simulations. [ABSTRACT FROM AUTHOR]

α‐Phase molybdenum trioxide(α‐MoO3) is a biaxial van der Waals semiconductor that can naturally support anisotropic phonon polaritons with elliptic and hyperbolic in‐plane dispersion. α‐MoO3 can meet critical coupling (CC) condition for both transverse magnetic (TM) and transverse electric (TE) polarizations along the x and y directions and exhibit high absorption in the mid‐infrared region due to strong phonon polaritons. In this study, an absorber composed of few‐layer α‐MoO3 and one‐dimensional photonic crystal separated by a cavity is proposed. Perfect absorption for TE and TM polarized light is achieved at the longitudinal and transverse optical phonon frequencies, respectively. The underlying mechanism of perfect absorption is investigated by using coupled mode theory and simulating electric field and power dissipation profiles. The results prove that CC is responsible for the perfect absorption. Moreover, the influence of the thickness of α‐MoO3 layer, width of cavity between α‐MoO3 and photonic crystal, and angle of incident light on the CC and absorption performance are examined. Accordingly, the rules for realizing perfect absorption at different operation frequencies are established. Overall, this study provides useful insights on designing a perfect absorber based on α‐MoO3 for detection and sensing applications in the mid‐infrared region. [ABSTRACT FROM AUTHOR]

Geometric phase enabled by spin‐orbit coupling has attracted enormous interest in optics over the past few decades. However, it is only applicable to circularly‐polarized light and encounters substantial challenges when applied to wave fields lacking the intrinsic spin degree of freedom. Here, a new paradigm is presented for achieving geometric phase by elucidating the concept of topological complementary pair (TCP), which arises from the combination of two compact phase elements possessing opposite intrinsic topological charge. Twisting the TCP leads to the generation of a linearly‐varying geometric phase of arbitrary order, which is quantified by the intrinsic topological charge. Notably distinct from the conventional spin‐orbit coupling‐based theories, the proposed geometric phase is the direct result of the cyclic evolution of orbital‐angular‐momentum transformation in mode space, thereby exhibiting universality across classical wave systems. As a proof of concept, the existence of this geometric phase is experimentally demonstrated using scalar acoustic waves, showcasing the remarkable ability in the precise manipulation of acoustic waves at subwavelength scales. These findings engender a fresh understanding of wave‐matter interaction in compact structures and establish a promising platform for exploring geometric phase, offering significant opportunities for diverse applications in wave systems. [ABSTRACT FROM AUTHOR]

In this paper, an ultra‐wideband metamaterial absorber (UWMA) is proposed and demonstrated by using a transparent and flexible sandwich structure, which consists of a top patterned double‐square loop (DSL) of conductive film, the polymer interlayer, the bottom conductive film. The work presents the UWMA's equivalent circuit model for a macroscopic analysis of its physical mechanism. Further, optimizing UWMA's structural parameters using this equivalent circuit model can greatly enhance its efficiency. The absorption coefficient of the designed structure achieves over 90% within the wide frequency range from 10.82 to 34.59 GHz due to the overlapping of three absorption bands. The experimental results indicate that the absorption coefficient of the fabricated structure exceeds 60% in the frequency range of 10.45–35.28 GHz, and reaches 90% in the majority of frequency range of 10.71–28.51 GHz, while its averaged optical transparency in the visible spectrum exceeds 75%. The UWMA achieves high transparency due to a small ratio of the surface area occupied by the ITO pattern to the total area and realizes multiple‐resonance ultra‐wideband absorption with conformality while maintaining a thickness of only 2.2 mm, which has diverse applications in the field of electromagnetics, including aircraft stealth, transparent chambers, and flexible electronic screens. [ABSTRACT FROM AUTHOR]

We present a theoretical study on enhancing the Faraday rotation of the monolayer phosphorus in a symmetric one-dimensional defective magneto-photonic crystal. The results show that by embedding the monolayer black phosphorus in the defect layer, the Faraday rotation angle can be significantly enhanced due to the defect mode of the magneto-photonic crystal that can strongly confine the electromagnetic field in the vicinity of the black phosphorus. The enhanced Faraday rotation angle may be increased in proportion to the external magnetic field while keeping the working wavelength and transmittance basically unchanged. The enhanced Faraday rotation can reach a gain of 20.9 dB with a transmission exceeding 60% with the applied magnetic field of 5 T after introducing the defect mode. Moreover, the Faraday rotation and the operating wavelength can be tunable using the width of the thickness of the defect layer, the incident angle, and the electron doping. • A defect magneto-photonic crystal has been designed to enhance the Faraday rotation (FR) of the monolayer phosphorus. • The FR is in proportional to the magnetic field while keeping the working wavelength and transmittance nearly unchanged. • The characteristics of the device can be tuned by the defect layer, the incident angle, and the electron doping. [ABSTRACT FROM AUTHOR]

In this work, we propose an efficient approach for controlling acoustic waves through guided mode conversion within a single meta-layer comprised of gradient index metamaterials. By harnessing the subwavelength localization characteristics of acoustic surface waves, the meta-layer can be properly shaped to accommodate arbitrary and prospective trajectories, thus enabling flexible guidance and routing of acoustic waves. Utilizing such a mode conversion mechanism, the acoustic directional transmitter and beam splitter have been devised and numerically demonstrated based on Archimedean spiral structures. These acoustic devices can exhibit a broadband response, achieving transmission efficiency exceeding 80% over a specific bandwidth that can be controlled by the geometry design. The proposed gradient index meta-layer may open new possibilities for acoustic wave manipulation, enabling some promising applications in noise control, information transmission, and energy harvesting. • A single meta-layer is proposed to realize guided mode conversion. • The meta-layer can be shaped to guide sound waves along prospective trajectories. • Acoustic devices using meta-layers exhibit a high efficiency over a wide bandwidth. [ABSTRACT FROM AUTHOR]

Although many multiplexed arrays of a superconducting nanowire single-photon detector (SNSPD) have been reported, it is still a major challenge to develop pixel-level readout arrays with high efficiency, parallel detection, and fast processing for real-time imaging. Here, we report a SNSPD array with inductor-shaping pulses for approaching the pixel-level readout. Optimized inductors are introduced to shape the output pulses of each pixel, and the response pulses of all pixels are synthesized in a series-connected structure. Then, the on/off states of all pixels can be encoded to the widths, amplitudes, and areas of the output pulses by the single-channel readout. This proposal is verified by a 4-pixel SNSPD array and a 16-pixel SNSPD array. It shows that the array not only inherits the features of the single-pixel SNSPD, such as photosensitive area, filling factor, quantum efficiency, and dark count rate, but also implements parallel operation of all pixels, which is always confused in traditional multiplexed SNSPD arrays. At the same time, the single-channel readout simplifies the system, and the serial digital signal converted from the shaped pulse enabled an easy and fast readout process, paving the way for high performance and real-time imaging. [ABSTRACT FROM AUTHOR]

Abstract: The preparation process, micro-structure and electrical properties of Pb(Zr x Ti1− x )O3 (PZT) thin films were investigated in this paper. The Ag/PZT(x =0.95)/YBCO/Si thin films were prepared by pulsed laser deposition (PLD). Si was the substrate; Ag and YBCO were the top electrode and the bottom electrode respectively. The bottom electrode YBCO was deposited on the Si substrate by PLD, and PZT was epitaxially deposited on YBCO also by PLD. After rapidly annealing, the AFM, XRD and the analysis of their electrical characters showed the films had good ferroelectric and pyroelectric properties. At 50°C, the pyroelectric coefficient (p) was 3.5×10−8 C/(cm2 K), the remanent polarization (Pr ) and the coercive field (Ec ) were 43.6μC/cm2 and 19.3kV/cm respectively. [Copyright &y& Elsevier]

In this Letter, we report on a device with which to resolve photon numbers and positions simultaneously, using single-channel readout from superconducting nanowire single-photon detectors (SNSPDs). The nanowires in the SNSPDs are connected in series with parallel resistors for producing response pulses with different amplitudes, whose values obey a distribution of 1:2:4:,..,2n-1. In single-photon detection, a saturated counting rate is obtained at a low dark count rate (<10 cps). Furthermore, we observed 16 output modes corresponding one-to-one with 16 states (15 photon responses + 1 state without photons) in multiphoton mode. This structure not only inherits the advantages of high quantum efficiency and low dark count rate of traditional SNSPD, but also realizes the resolution of photon position and number simultaneously without complicated optical system. Thus, this proposal offers a promising platform for realizing scalable and practical quantum information chips. [ABSTRACT FROM AUTHOR]

It is a big challenge for lidar to detect soft targets over long distances in the atmosphere due to the low reflection of soft targets and the strong atmospheric attenuation. In this paper, we propose an all-day lidar system based on the 4 pixel array superconducting nanowire single-photon detectors. This significantly improves the detection efficiency of the aerosol and other targets by utilizing the advantages of high sensitivity, low dark count rate, wide dynamic range and photon number resolution. The system detects both soft targets and hard targets 100 km away in the atmosphere. In experiments, based on the photon-number resolving detection method, the lidar detects and distinguishes soft and hard targets simultaneously 50 km away during the day. Furthermore, the system obtains the wind field information in the atmosphere by monitoring clouds at a distance exceeding 86 km. The detection results indicate that the system is promising for applications as a long distance all-day lidar. [ABSTRACT FROM AUTHOR]

We propose a tunable multichannel plasmonic mid-infrared filter of a single graphene sheet depositing on a Fibonacci quasiperiodic structure. The transmission spectra are numerically analyzed by a finite-difference time-domain (FDTD) method, and the results show that the filtering properties of the proposed structure can be tuned by the chemical potentials of graphene, the width and depth of air grooves, and the refractive index of the substrate. The simulation results are discussed analytically by deducing the dispersion relation of surface plasmon polariton propagating on four layers structure of air/graphene/air/dielectric. The proposed structure may find potential applications in tunable filters, sensors, and integrated photonic circuits. [ABSTRACT FROM AUTHOR]

We theoretically propose a system capable of wavelength-tunable sub-diffraction-limited imaging by a single planar magnetic superlens, which is made of -negative ferrite material (MNM) slab. Our theoretical and numerical simulation results demonstrate that the working wavelength of this planar superlens can be well tuned with the external magnetic field since the permeability of ferrite material LuBiIG is adjusted by the applied magnetic field. The resolution of the magnetic superlens with 300 m thickness LuBiIG film is smaller than /20, and the resolution is higher with thinner film. It may provide a potential way to design a wavelength-tunable magnetic superlens with the single layer of ferrite thin film material. [ABSTRACT FROM AUTHOR]

Abstract: The preparation process, crystallinity and electrical properties of pulse laser deposited Pb(Zr x Ti1− x )O3 (PZT) thin films were investigated in this paper. PZT (x =0.93) thin film samples deposited at different substrate temperatures were prepared. Si (110) was the substrate; Ag and YBCO were the top electrode and the bottom electrode respectively. The bottom electrode YBCO was deposited on the Si substrate by pulsed laser deposition (PLD), and then PZT was epitaxially deposited on YBCO also by PLD. After annealing, the top electrode Ag was prepared on PZT by thermal evaporation, and then the Ag/PZT/YBCO/Si structured thin films were obtained. The XRD and the analysis of their electrical characters showed that, when the substrate temperature was elevated from 600°C to 800°C, the crystallinity and electrical properties of PZT thin films became better and better, and the F R(LT)–F R(HT) phase transition of PZT (x =0.93) thin films occurred at 62°C. The PZT film deposited at 800°C had the best pyroelectric properties, and when the F R(LT)–F R(HT) phase transition of this film occurred, the peak value of pyroelectric coefficient (p) was obtained, with a value of 1.96×10−6 C/(cm2 K). The PZT film deposited at 800°C had the highest remnant polarization (P r) and the lowest coercive field (E c), with the values of 34.3μC/cm2 and 41.7kV/cm respectively. [Copyright &y& Elsevier]