Catálogo de publicaciones - revistas

<jats:p>This paper conducts a trade-off between efficiency and accuracy of three-dimensional (3D) shape measurement based on the triangulation principle, and introduces a flying and precise 3D shape measurement method based on multiple parallel line lasers. Firstly, we establish the measurement model of the multiple parallel line lasers system, and introduce the concept that multiple base planes can help to deduce the unified formula of the measurement system and are used in simplifying the process of the calibration. Then, the constraint of the line spatial frequency, which maximizes the measurement efficiency while ensuring accuracy, is determined according to the height distribution of the object. Secondly, the simulation analyzing the variation of the systemic resolution quantitatively under the circumstance of a set of specific parameters is performed, which provides a fundamental thesis for option of the four system parameters. Thirdly, for the application of the precision measurement in the industrial field, additional profiles are acquired to improve the lateral resolution by applying a motor to scan the 3D surface. Finally, compared with the line laser, the experimental study shows that the present method of obtaining 41220 points per frame improves the measurement efficiency. Furthermore, the accuracy and the process of the calibration are advanced in comparison with the existing multiple-line laser and the structured light makes an accuracy better than 0.22 mm at a distance of 956.02 mm.</jats:p>

<jats:p>In the unresolved sideband regime, we propose a scheme for cooling mechanical resonator close to its ground state in a three-cavity optomechanical system, where the auxiliary cavities are indirectly connected with the mechanical resonator through standard optomechanical subsystem. The standard optomechanical subsystem is driven by a strong pump laser field. With the help of the auxiliary cavities, the heating process is suppressed and the cooling process of the mechanical resonator is enhanced. More importantly, the average phonon number is much less than 1 in a larger range. This means that the mechanical resonator can be cooled down to its ground state. All these interesting features will significantly promote the physical realization of quantum effects in multi-cavity optomechanical systems.</jats:p>

<jats:p>The symmetric Ti/Au bi-layer point electrodes have been successfully patterned on the <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> films which are prepared by metal–organic chemical vapor deposition (MOCVD) and the <jats:italic>γ</jats:italic>-CuI films which are prepared by spin-coating. The fabricated heterojunction has a large open circuit voltage (<jats:italic>V</jats:italic> <jats:sub>oc</jats:sub>) of 0.69 V, desired for achieving self-powered operation of a photodetector. Irradiated by 254-nm ultraviolet (UV) light, when the bias voltage is –5 V, the dark current (<jats:italic>I</jats:italic> <jats:sub>dark</jats:sub>) of the device is 0.47 pA, the photocurrent (<jats:italic>I</jats:italic> <jats:sub>photo</jats:sub>) is –50.93 nA, and the photo-to-dark current ratio (<jats:italic>I</jats:italic> <jats:sub>photo</jats:sub>/<jats:italic>I</jats:italic> <jats:sub>dark</jats:sub>) reaches about 1.08 × 10<jats:sup>5</jats:sup>. The device has a stable and fast response speed in different wavelengths, the rise time (<jats:italic>τ</jats:italic> <jats:sub>r</jats:sub>) and decay time (<jats:italic>τ</jats:italic> <jats:sub>d</jats:sub>) are 0.762 s and 1.741 s under 254-nm UV light illumination, respectively. While the <jats:italic>τ</jats:italic> <jats:sub>r</jats:sub> and <jats:italic>τ</jats:italic> <jats:sub>d</jats:sub> are 10.709 s and 7.241 s under 365-nm UV light illumination, respectively. The time-dependent (<jats:italic>I</jats:italic>–<jats:italic>t</jats:italic>) response (photocurrent in the order of 10<jats:sup>−10</jats:sup> A) can be clearly distinguished at a small light intensity of 1 μW⋅cm<jats:sup>−2</jats:sup>. The internal physical mechanism affecting the device performances is discussed by the band diagram and charge carrier transfer theory.</jats:p>

<jats:p>High-dimensional entanglement provides valuable resources for quantum technologies, including quantum communication, quantum optical coherence tomography, and quantum computing. Obtaining a high brightness and dimensional entanglement source has significant value. Here we utilize a tunable asymmetric Mach–Zehnder interferometer coupled silicon microring resonator with 100 GHz free spectral range to achieve this goal. With the strategy of the tunable coupler, the dynamical and extensive tuning range of quality factors of the microring can be obtained, and then the biphoton pair generation rate can be optimized. By selecting and characterizing 28 pairs from a more than 30-pair modes biphoton frequency comb, we obtain a Schmidt number of at least 23.4 and on-chip pair generation rate of 19.9 MHz/mW<jats:sup>2</jats:sup> under a low on-chip pump power, which corresponds to 547 dimensions Hilbert space in frequency freedom. These results will prompt the wide applications of quantum frequency comb and boost the further large density and scalable on-chip quantum information processing.</jats:p>

<jats:p>We propose a hybrid structure of a nano-cube array coupled with multilayer full-dielectric thin films for refractive index sensing. In this structure, discrete states generated by two-dimensional grating and continuous states generated by a photonic crystal were coupled at a specific wavelength to form two Fano resonances. The transmission spectra and electric field distributions of the structure were obtained via the finite-difference time-domain method. We obtained the optimal structural parameters after optimizing the geometrical parameters. Under the optimal parameters, the figure of merit (FOM) values of the two Fano resonances reached 1.7 × 10<jats:sup>4</jats:sup> and 3.9 × 10<jats:sup>3</jats:sup>, respectively. These results indicate that the proposed structure can achieve high FOM refractive index sensing, thus offering extensive application prospects in the biological and chemical fields.</jats:p>

<jats:p>We investigate the role of aging temperature on relaxation of internal friction in Zr<jats:sub>59</jats:sub>Fe<jats:sub>18</jats:sub>Al<jats:sub>10</jats:sub>Ni<jats:sub>10</jats:sub>Nb<jats:sub>3</jats:sub> metallic glass. For this purpose, dynamic mechanical analysis with different annealing temperatures and frequency values is applied. The results indicate that the aging process leads to decrease in the dissipated energy in the temperature range of glass transition. It is also found that the increase in applied frequency weakens the loss factor intensity in the metallic glass. Moreover, the Kohlrausch–Williams–Watts (KWW) equation is used to evaluate the evolution of internal friction during the aging process. According to the results, higher annealing temperature will make the primary internal friction in the material increase; however, a sharp decline is observed with the time. The drop in characteristic time of internal friction is also closely correlated to the rate of atomic rearrangement under the dynamic excitation so that at higher annealing temperatures, the driving force for the collaborative movement of atoms is easily provided and the mean relaxation time significantly decreases.</jats:p>

<jats:p>The commercial 42M Nd–Fe–B magnet was treated by grain boundary diffusion (GBD) with Pr<jats:sub>70</jats:sub>Co<jats:sub>30</jats:sub> (PC), Pr<jats:sub>70</jats:sub>Al<jats:sub>30</jats:sub> (PA) and Pr<jats:sub>70</jats:sub>Co<jats:sub>15</jats:sub>Al<jats:sub>15</jats:sub> (PCA) alloys, respectively. The mechanism of coercivity enhancement in the GBD magnets was investigated. The coercivity was enhanced from 1.63 T to 2.15 T in the PCA GBD magnet, higher than the 1.81 T of the PC GBD magnet and the 2.01 T of the PA GBD magnet. This indicates that the joint addition of Co and Al in the diffusion source can further improve the coercivity. Microstructural investigations show that the coercivity enhancement is mainly attributed to the exchange-decoupling of the GB phases. In the PCA GBD magnet, the wider thin GB phases can be formed and the thin GB phases can still be observed at the diffusion depth of 1500 μm due to the combined action of Co and Al. At the same time, the formation of the Pr-rich shell can also be observed, which is helpful for the coercivity enhancement.</jats:p>

<jats:p>To fully release the potential of wide bandgap (WBG) semiconductors and achieve high energy density and efficiency, a carbonyl iron soft magnetic composite (SMC) with an easy plane-like structure is prepared. Due to this structure, the permeability of the composite increases by 3 times (from 7.5 to 21.5) at 100 MHz compared with to the spherical carbonyl iron SMC, and the permeability changes little at frequencies below 100 MHz. In addition, the natural resonance frequency of the composite shifts to higher frequencies at 1.7 GHz. The total core losses of the composites at 10, 20, and 30 mT are 80.0, 355.3, and 810.7 mW/cm<jats:sup>3</jats:sup>, respectively, at 500 kHz. Compared with the spherical carbonyl iron SMC, the core loss at 500 kHz is reduced by more than 60%. Therefore, this kind of soft magnetic composite with an easy plane-like structure is a good candidate for unlocking the potential of WBG semiconductors and developing the next-generation power electronics.</jats:p>

<jats:p>The spontaneous emission rate of a two-level quantum emitter (QE) near a gold nanorod is numerically investigated. Three different optical response models for the free-electron gas are adopted, including the classical Drude local response approximation, the nonlocal hydrodynamic model, and the generalized nonlocal optical response model. Nonlocal optical response leads to a blueshift and a reduction in the enhancement of the spontaneous emission rate. Within all the three models, the resonance frequency is largely determined by the aspect ratio (the ratio of the nanorod length to the radius) and increases sharply with decreasing aspect ratio. For nanorod with a fixed length, it is found that the larger the radius is, the higher the resonance frequency is, and the smaller the enhancement is. However, if the length of the nanorod increases, the peak frequency falls sharply, while the spontaneous emission enhancement grows rapidly. For nanorod with a fixed aspect ratio, the peak frequency decreases slowly with increasing nanorod size. Larger nanorod shows smaller nonlocal effect. At a certain frequency, there is an optimal size to maximize the enhancement of the spontaneous emission rate. Higher order modes are more affected by the nonlocal smearing of the induced charges, leading to larger blueshift and greater reduction in the enhancement. These results should be significant for investigating the spontaneous emission rate of a QE around a gold nanorod.</jats:p>

<jats:p>The secondary electron emission yields of materials depend on the geometries of their surface structures. In this paper, a method of depositing vertical graphene nanosheet (VGN) on the surface of the material is proposed, and the secondary electron emission (SEE) characteristics for the VGN structure are studied. The COMSOL simulation and the scanning electron microscope (SEM) image analysis are carried out to study the secondary electron yield (SEY). The effect of aspect ratio and packing density of VGN on SEY under normal incident condition are studied. The results show that the VGN structure has a good effect on suppressing SEE.</jats:p>