Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Recently, a Rydberg atom-based mixer was developed to measure the phase of a radio frequency (RF) field. The phase of the signal RF (SIG RF) field is down-converted directly to the phase of a beat signal created by the presence of a local RF (LO RF) field. In this study, we propose that the Rydberg atom-based mixer can be converted to an all optical phase detector by amplitude modulation (AM) of the LO RF field; that is, the phase of the SIG RF field is related to both the amplitude and phase of the beat signal. When the AM frequency of the LO RF field is the same as the frequency of the beat signal, the beat signal will further interfere with the AM of the LO RF field inside the atom, and then the amplitude of the beat signal is related to the phase of the SIG RF field. The amplitude of the beat signal and the phase of the SIG RF field show a linear relationship within the range of 0 to <jats:italic>π</jats:italic>/2 when the phase of the AM is set with a difference <jats:italic>π</jats:italic>/4 from the phase of the LO RF field. The minimum phase resolution can be as small as 0.6 degree by optimizing the experimental conditions according to a simple theoretical model. This study will expand and contribute to the development of RF measurement devices based on Rydberg atoms.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A scheme of storage of cold molecules with hollow optical ring generated by the metasurface grating is proposed. The characteristics and intensity distribution related to the ring’s structural parameters alongside the fabrication-error tolerance are theoretically studied. The optical potential and dipole force for the ring to trap magnesium monofluoride (MgF) molecules are also calculated. The dynamical behavior of MgF molecules in the storage ring is simulated by a Monte-Carlo method, which shows that the metasurface-based optical storage ring is applicable to trap molecules and can be an interesting platform for the research of ultracold quantum gases and their quantum-state manipulation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Terahertz wave is between microwave and infrared bands in the electromagnetic spectrum with the frequency range from 0.1 THz to 10 THz. Control and processing of the polarization state in terahertz wave is the focus due to the great influence on its characteristics. In this paper, a transmissive metasurface terahertz polarization converter is designed in 3D structure with an upper surface of ruler-like rectangular, an intermediate dielectric layer and a lower surface of metal grid wires. Numerical simulations of the converter show that the polarization conversion rate (PCR) is above 99.9% at 0.288-1.6 THz, the polarization rotation angle (PRA) is close to 90o at 0.06-1.4 THz, and the ellipticity angle (EA) is close to 0o at 0.531-1.49 THz. The origin of the efficient polarization conversion is explained by analyzing the electric field intensity, magnetic field intensity, surface current, electric field energy density, and magnetic field energy density distributions of the converter at 1.19 THz and 0.87 THz, which is consistent with the energy transmittance and transmittance coefficient.. In addition, the effect of different thickness and material of intermediate layer, thickness of upper surface material, polarized wave incidence angle, and metasurface materials on the performance of the polarization converter is discussed, and the reasons to affect the conversion performance of the polarization converter are also explained. Our results provide a strong theoretical basis and technical support to develope high performance of transmission-type terahertz polarization converters, and play an important role to promote the development of terahertz science and technology.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Amorphous In-Ga-Zn-O (a-IGZO) thin-film transistor (TFT) memories with novel p-SnO/n-SnO<jats:sub>2</jats:sub> heterojunction charge trapping stacks (CTSs) are investigated comparatively under a maximum fabrication temperature of 280 ℃. Compared to a single p-SnO or n-SnO<jats:sub>2</jats:sub> charge trapping layer (CTL), the heterojunction CTSs can achieve electrically programmable and erasable characteristics as well as good data retention. Of the two CTSs, the tunneling layer/p-SnO/n-SnO<jats:sub>2</jats:sub>/blocking layer architecture demonstrates a much higher program efficiency, more robust data retention, and comparably superior erase characteristics. The resulting memory window is as large as 6.66 V after programming at 13 V/1 ms and erasing at -8 V/1 ms, and the ten-year memory window is extrapolated to be 4.41 V. This is attributed to shallow traps in p-SnO and deep traps in n-SnO<jats:sub>2</jats:sub>, and the formation of built-in electric field in the heterojunction.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we propose a new scheme to enhance the performance of the Gussian-modulated coherent state(GMCS) continuous-variable measurement-device-independent quantum key distribution(CV-MDI-QKD) system via quantum scissors(QS) operation at Bob’s side. As an non-deterministic amplifying setup, we firstly introduce the QS-enhanced CV-MDI-QKD protocol and then investigate the success probability of the QS operation in accordance with the equivalent one-way scheme. Afterwards, we investigate the effect of the QS operation on the proposed scheme and analyze the performance of the QS-enhanced CV-MDI-QKD system under the extreme asymmetric circumstance. Simulation results show that the QS operation can indeed improve the performance of the CV-MDI-QKD system considerably. QS-enhanced CV-MDI-QKD protocol outperforms the original CV-MDI-QKD protocol in both the maximum transmission distance and the secret key rate. Moreover, the better the performance of QS operation, the more significant improvement of the performance of the system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The fine and hyperfine structure of pionic helium metastable states is calculated within the formalism of the Breit-Pauli Hamiltonian using variationally generated wave functions in Hylleraas coordinates. Our results not only verify the existing values of Hori <jats:italic>et al</jats:italic>.[Phys. Rev. A <jats:bold>89</jats:bold>, 042515 (2014)] for the fine structure of <jats:italic>π</jats:italic> <jats:sup>4</jats:sup>He<jats:sup>+</jats:sup>, but also determine the hyperfine structure of <jats:italic>π</jats:italic> <jats:sup>3</jats:sup>He<jats:sup>+</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The photodetectors based on two-dimensional (2D) materials have drawn much attention because of the unique properties. To further improve the performance of self-driven photodetectors based on van der Waals heterojunction, the conductive band minimum (CBM) matched self-driven SnS<jats:sub>2</jats:sub>/WS<jats:sub>2</jats:sub> van der Waals heterojunction photodetector based on SiO<jats:sub>2</jats:sub>/Si substrate has been designed. The device exhibits a positive current at zero voltage under 365 nm laser illumination. This is attributed to the built-in electric field at the interface of SnS<jats:sub>2</jats:sub> and WS<jats:sub>2</jats:sub> layer, which will separate and transport the photogenerated carriers even at zero bias voltage. In addition, the Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> layer is covered with the surface of the SnS<jats:sub>2</jats:sub>/WS<jats:sub>2</jats:sub> photodetector to further improve the performance, because the Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> layer will introduce the tensile stress on the surface of the 2D materials leading to higher electron concentration and smaller effective mass of electrons of the films. This work provides an idea for the research of self-driven photodetector based on van der Waals heterogeneous junction.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-resolution images of human brain are critical for monitoring the neurological conditions in a portable and safe manner. Sound speed mapping of brain tissues provides unique information for such purpose. In addition, it is particularly important for building digital human acoustic models, which form a reference for future ultrasound research. Conventional ultrasound modalities can hardly image the human brain at high spatial resolution inside the skull, due to the strong impedance contrast between hard and soft tissues. We carry out numerical experiments to illustrate that the time-domain waveform inversion technique, originating from the geophysics community, is promising to deliver quantitative images of human brains with-in the skull at the sub-millimeter level using ultra-sound signals. The success implementation of such approach to brain imaging requires the following: signals of sub-megahertz frequencies transmitting across the inside of skull, an accurate numerical wave equation solver simulating the wave propagation, and well-designed inversion schemes to reconstruct the physical parameters of targeted model based on the optimization theory. Here we propose an innovative modality of multiscale deconvolutional waveform inversion that improves ultrasound imaging resolution, by evaluating the similarity of synthetic and observed data using limited length wiener filter. We perform the proposed approach to iteratively update the para-metric models of the human brain. As a quantitative imaging method, it paves the way for building the accurate acoustic brain model to diagnose associated diseases, in a potentially more portable, more dynamic and safer way compared to magnetic resonance imaging and X-ray computed tomography.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The diffusion and activation of phosphorus in phosphorus and fluorine co-implanted Ge after excimer laser annealing was investigated firstly. The results prove that the fluorine element plays an important role in suppressing phosphorus diffusion and enhancing phosphorus activation. Moreover, the rapid thermal annealing process had been also utilized to evaluate and verify the role of fluorine element. During the initial annealing of co-implanted Ge, it was easier to form high bonding energy F<jats:sub>n</jats:sub>V<jats:sub>m</jats:sub> clusters which could stabilize the excess vacancies resulting in the reduced vacancy-assisted diffusion of phosphorus. The maximum activation concentration of about 4.4×10<jats:sup>20</jats:sup> /cm<jats:sup>3</jats:sup> with a reduced diffusion length and dopant loss was achieved in co-implanted Ge that was annealed at a tailored laser fluence of 175 mJ/cm<jats:sup>2</jats:sup>. The combination of excimer laser annealing and co-implantation technique provides a reference and guideline for high level n-type doping in Ge and is beneficial to its application in the scaled Ge MOSFET technology and other devices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Nowadays, soft robots have become a research hotspot due to high degree of freedom, adaptability to the environment and safer interaction with humans. The carbon nanotube (CNT)/polydimethylsiloxane (PDMS) electrothermal composites have attracted wide attention in the field of flexible actuations due to large deformation at low voltages. Here, the preparation process of CNT/PDMS composites was designed and optimized, and electrothermal actuators (ETAs) were fabricated by cutting the CNT/PDMS composite films into a "U" shape and coating conductive adhesive. The deformation performance of the ETAs with different thicknesses at different voltages was studied. At a low voltage of about 7 V, the ETA has a deformation rate of up to 93%. Finally, two kinds of electrothermal soft robots (ETSRs) with four-legged and three-legged structures were fabricated, and their inchworm-like motion characteristics were studied. The ETSR2 has the best motion performance due to the moderate thickness and three-legged electrode structure.</jats:p>