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Metasurface has garnered extensive attention across multiple disciplines owing to its profound capability in electromagnetic (EM) manipulations. To determine its EM characteristics accurately, full-wave simulations are essential. These simulations necessitate significant amounts of time and memory resources, hindering the efficiency of the design process. In this article, we propose MetaPhyNet, a novel physics-driven neural network based on temporal coupled-mode theory (CMT) to address the challenges of low efficiency and high memory consumption in large-scale metasurface design. In the proposed approach, a surrogate model is developed to achieve rapid prediction of the EM responses of ultra-large-scale metasurfaces. In comparison with the full-wave EM simulation, the proposed model reduces the simulation time of the ultra-large-scale metasurface by up to two orders of magnitude and the memory consumption by more than two orders of magnitude. Our proposed approach aims to enhance the efficiency and intelligence in metasurface design by leveraging the principles of CMT within a neural network framework. Through this innovative integration of physics-based modeling and machine learning, we seek to achieve significant advancements in the design efficiency of metasurfaces. We apply the proposed model to optimize the design of two metasurface absorbers to showcase the effectiveness of our proposed approach. Simulations and experimental results are provided to demonstrate the value and impact of our approach in addressing existing challenges in full-wave EM simulation-based design optimizations of metasurfaces.

Optical nanoantennas have attracted significant attention over the past decades, owing to their exceptional capabilities in terms of light manipulation and versatile optical applications. Recently, active nanoantennas have been developed by introducing phase change materials, to achieve specific tunable electromagnetic responses. However, most of these attempts only function with ‘ON’/‘OFF’ states or switch in a few discrete states, significantly restricting the application in dynamic tunability. Thus far, the continuous and reversible modulation of optical nanoantennas has not been sufficiently explored. In this article, we experimentally demonstrate a continuously and reversibly electro-tunable optical nanoantenna, by integrating an asymmetric gold nanodisk dimer array with a vanadium dioxide (VO _2 ) film and graphene thin film. By accurately controlling the applied electrical current, the Joule heat generated in the graphene film excites the metal-insulator phase transition of VO _2 , and the refractive index of VO _2 exhibits a relatively large variation. When VO _2 is in the insulating phase, we observe an apparent resonance dip in the reflection spectrum, which is attributed to a hybrid mode originating from the gap plasmon in the dimers and localized surface plasmon (LSP) resonance excited at the edge of the nanodisks. Meanwhile, owing to the coupling between two asymmetric LSP resonances in the neighboring nanodisks, the reflected peak based on the Fano effect is realized. However, once VO _2 is in the metallic phase, the hybrid mode becomes weaker and red-shifted, and the Fano effect disappears. Thereafter, the continuous and reversible electro-modulation of the nanoantenna features, including the resonant wavelength, resonant intensity, and quality factors ( Q ), are experimentally verified in the optical communication region, by varying the applied electrical current in the hybrid structure. To further increase the modulation range of these properties, we scan the gap size and structural asymmetry parameter of the nanodisk dimer. The results show that, with a smaller gap size, the resonant intensity of the nanoantenna is stronger. When the structural asymmetry parameter increases, the resonant wavelength is redshifted. We expect that such continuously and reversibly electro-tunable nanoantennas will stimulate various applications in optical communication systems, tunable photoelectric sensors, and beyond.

We theoretically study the Casimir interaction between Weyl semimetals. When the distance a between semi-infinite Weyl semimetals is in the micrometer regime, the Casimir attraction can be enhanced by the chiral anomaly. The Casimir attraction depends sensitively on the relative orientations between the separations (b 1, b 2) of Weyl nodes in the Brillouin zone and show anisotropic behavior for the relative orientation of these separations (b 1, b 2) when they orient parallel to the interface. This anisotropy is quite larger than that in conventional birefringent materials. The Casimir force can be repulsive in the micrometer regime if the Weyl semimetal slabs are sufficiently thin and the direction of Weyl nodes separations (b 1, b 2) is perpendicular to the interface. The Casimir attraction between Weyl semimetal slabs decays slower than 1/a4 when the Weyl nodes separations b 1 and b 2 are both parallel to the interface. [ABSTRACT FROM AUTHOR]

MAXI J1820+070 is a newly discovered black hole X-ray binary, whose dynamical parameters, namely the black hole mass, the inclination angle, and the source distance, have recently been estimated. Insight-HXMT have observed its entire outburst from 2018 March 14. In this work, we attempted to estimate the spin parameter a*, using the continuum-fitting method and applying a fully relativistic thin disk model to the soft-state spectra obtained by Insight-HXMT. It is well known that a* is strongly dependent on three dynamical parameters in this method, and we have examined two sets of parameters. Adopting our preferred parameters: M = , i = 63° ± 3°, and D = 2.96 ± 0.33 kpc, we found a slowly spinning black hole of a* = 0.14 ± 0.09 (1σ), which gives a prograde spin parameter as the majority of other systems show. It is also possible for the black hole to have a retrograde spin (less than 0) if different dynamical parameters are taken. [ABSTRACT FROM AUTHOR]

Optical nanoantennas have attracted significant attention over the past decades, owing to their exceptional capabilities in terms of light manipulation and versatile optical applications. Recently, active nanoantennas have been developed by introducing phase change materials, to achieve specific tunable electromagnetic responses. However, most of these attempts only function with 'ON'/'OFF' states or switch in a few discrete states, significantly restricting the application in dynamic tunability. Thus far, the continuous and reversible modulation of optical nanoantennas has not been sufficiently explored. In this article, we experimentally demonstrate a continuously and reversibly electro-tunable optical nanoantenna, by integrating an asymmetric gold nanodisk dimer array with a vanadium dioxide (VO2) film and graphene thin film. By accurately controlling the applied electrical current, the Joule heat generated in the graphene film excites the metal-insulator phase transition of VO2, and the refractive index of VO2 exhibits a relatively large variation. When VO2 is in the insulating phase, we observe an apparent resonance dip in the reflection spectrum, which is attributed to a hybrid mode originating from the gap plasmon in the dimers and localized surface plasmon (LSP) resonance excited at the edge of the nanodisks. Meanwhile, owing to the coupling between two asymmetric LSP resonances in the neighboring nanodisks, the reflected peak based on the Fano effect is realized. However, once VO2 is in the metallic phase, the hybrid mode becomes weaker and red-shifted, and the Fano effect disappears. Thereafter, the continuous and reversible electro-modulation of the nanoantenna features, including the resonant wavelength, resonant intensity, and quality factors (Q), are experimentally verified in the optical communication region, by varying the applied electrical current in the hybrid structure. To further increase the modulation range of these properties, we scan the gap size and structural asymmetry parameter of the nanodisk dimer. The results show that, with a smaller gap size, the resonant intensity of the nanoantenna is stronger. When the structural asymmetry parameter increases, the resonant wavelength is redshifted. We expect that such continuously and reversibly electro-tunable nanoantennas will stimulate various applications in optical communication systems, tunable photoelectric sensors, and beyond. [ABSTRACT FROM AUTHOR]

We simultaneously compare the probe transmission, Four-Wave Mixing (FWM) and fluorescence signals with dressing effects in a four-level atomic system. The variation rules of three types of signals are exhibited by changing the frequency detuning and power of incident laser beams. The interplay between two ladder subsystems is investigated in the Y-type atomic system. In particular, the fluorescence signal with ultra-narrow linewidth is obtained due to being sheared twice by the electromagnetically induced transparency window. Such fluorescence with very high coherence and monochromaticity can be used for the quantum correlation and narrow linewidth laser. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into the impact of proton-induced alteration of carrier lifetime on the single-event transient (SET) caused by heavy ions in silicon–germanium heterojunction bipolar transistor (SiGe HBT). The ion-induced current transients and integrated charge collections under different proton fluences are obtained based on technology computer-aided design (TCAD) simulation. The results indicate that the impact of carrier lifetime alteration is determined by the dominating charge collection mechanism at the ion incident position and only the long-time diffusion process is affected. With a proton fluence of 5×1013 cm−2, almost no change is found in the transient feature, and the charge collection of events happened in the region enclosed by deep trench isolation (DTI), where prompt funneling collection is the dominating mechanism. Meanwhile, for the events happening outside DTI where diffusion dominates the collection process, the peak value and the duration of the ion-induced current transient both decrease with increasing proton fluence, leading to a great decrease in charge collection. [ABSTRACT FROM AUTHOR]

In this paper we investigate two techniques for single event effect (SEE) mitigation by using back junction and p+ buffer layer in non-deep trench isolation (DTI) domestic silicon–germanium heterojunction bipolar transistors (SiGe HBTs) based on technology computer aided design (TCAD) simulation. The effectiveness of the two mitigation techniques and the influence of various structure parameters are investigated. Simulation results indicate that the two techniques are more effective in reducing collector charge collection induced by heavy ions striking at positions outside the collector–substrate (C–S) junction where charge collection is dominated by diffusion. By properly adjusting the parameters, charge collection of events outside the C–S junction can be reduced by more than an order of magnitude, while charge collection of events in the device center is halved without affecting the direct current (DC) and alternating current (AC) characteristics of the SiGe HBTs. [ABSTRACT FROM AUTHOR]

We proposed a two-degrees-of-freedom inverted piezoelectric beam with pendulum to promote the performance of vibration energy harvesting. This configuration is composed of an inverted elastic beam and a pendulum attached to its free end. The electromechanical equations governing the nonlinear system were derived. The harmonic balance method (HBM) is applied to solve the equation and the results prove that there exists a 1:3 super-harmonic resonance. The simulation results show that owing to the particular nonlinearity, there appears a special bending effect in the amplitude-frequency response, i.e., bending right for the first natural frequency and left for the second natural frequency, which is beneficial for harvesting vibration energy. The HBM results are verified by the entity simulations. Furthermore, over a relatively wide range of power spectral density, it could reach a dense jumping and give a dense high pulse voltage. [ABSTRACT FROM AUTHOR]

As the feature size of the device decreases, the critical charge decreases gradually and the influence of radiation particles becomes more and more serious, especially the single event upset (SEU). Some previously unknown radiation damage began to appear as the size of the device decreased. Low energy protons undergoing direct ionization can induce SEU in 65 nm static random access memories (SRAM), and muons can induce errors as a function of incident muon energy. In this work, the radiation damage caused by X-ray to the 45 nm SRAM is studied through experiments. The sensitive volume of SRAM is constructed using Monte Carlo radiation transport code Geant4 to analyze the effects of critical charge and metal interconnect overlayers of different materials. The experimental results suggested that under the low power state, the secondary electrons produced by the X-ray can induce upsets, lower the voltage, and increase the number of errors. Monte Carlo simulation shows that as the critical charge decreased, SEU becomes more severe. At the same time, photons interact with high atomic number materials in the metal interconnect overlayers, which could generate more secondary electrons resulting in the SEU cross section rising to a higher value. [ABSTRACT FROM AUTHOR]

The impact of ionizing radiation effect on single event upset (SEU) sensitivity of ferroelectric random access memory (FRAM) is studied in this work. The test specimens were firstly subjected to 60Co γ-ray and then the SEU evaluation was conducted using 209Bi ions. As a result of TID-induced fatigue-like and imprint-like phenomena of the ferroelectric material, the SEU cross sections of the post-irradiated devices shift substantially. Different trends of SEU cross section with elevated dose were also found, depending on whether the same or complementary test pattern was employed during the TID exposure and the SEU measurement. [ABSTRACT FROM AUTHOR]

We present a first-principles study of the structural, dielectric, and lattice dynamical properties for chalcopyrite semiconductor ZnSnP2. The structural properties are calculated using a plane-wave pseudopotential method of density-functional theory. A linear response theory is used to derive Born effective charge tensors for each atom, dielectric constants in low and high frequency limits, and phonon frequencies. We calculate all zone-center phonon modes, identify Raman and infrared active modes, and report LO–TO splitting of the infrared modes. The results show an excellent agreement with experiment and propose several predictive behaviors. [ABSTRACT FROM AUTHOR]

Since the displacement damage induced by the neutron irradiation prior has negligible impact on the performance of the bulk CMOS SRAM, we use the neutron irradiation to degrade the minority carrier lifetime in the regions responsible for latchup. With the experimental results, we discuss the impact of the neutron-induced displacement damage on the SEL sensitivity and qualitative analyze the effectiveness of this suppression approach with TCAD simulation. [ABSTRACT FROM AUTHOR]

For obtaining pure phase Tl2Ba2Ca2Cu3O10 (Tl-2223) films with good superconducting properties, the growth technique is improved by dc magnetron sputtering and a triple post-annealing process. The triple post-annealing process comprises annealing twice in argon and once in oxygen at different temperatures. In the first low-temperature annealing phase in argon, Tl2Ba2CaCu2O8 (Tl-2212) is obtained to effectively minimize evaporation in the next step. With the increase of temperature in the second annealing stage in argon, the previously prepared Tl-2212 inter-phase is converted into Tl-2223 phase. An additional annealing in oxygen is also adopted to improve the properties of Tl-2223 films, each containing an optimal oxygen content value. The results of X-ray diffraction (XRD) θ–2θ scans, ω scans and rotational φ scans show that each of the Tl-2223 films has a high phase purity and an epitaxial structure. Smooth films are observed by scanning electron microscopy (SEM). The critical temperatures Tc of the films are measured to be about 120 K and the critical current densities Jc can reach 4.0 MA/cm2 at 77 K at self field. [ABSTRACT FROM AUTHOR]

A simple clock enhanced loop of cascaded electro-absorption modulators (EAMs) and 10 GHz clock recovery modules is presented. The intensity of harmonic of clock-frequency component is analyzed theoretically and verified experimentally in a 160 Gb/s OTDM 100 km transmission system. The 10 GHz clock component is enhanced obviously before launching into the clock recovery module and the recovered clock signal exhibits low rms jitter of < 400 fs. Moreover, completely error-free (10[?]12) transmission is observed for more than two hours without using forward error correction technology. The power penalty is about 3.6 dB. The proposed loop has merits of enhancing base clock component, simultaneously de-multiplexing and clock recovery, which make the performance of this loop more stable and high suppression of non-target channels. [ABSTRACT FROM AUTHOR]