Markerjoyner6052

A tunable broadband terahertz (THz) absorber based on vanadium dioxide ($\rm VO_2$) and graphene is proposed. The absorber, consisting of the $\rm VO_2$ square loop, polymethacrylimide (PMI) dielectric layer, and a layer of unpatterned graphene, can achieve absorption over 90% from 1.04 THz to 5.51 THz and relative bandwidth of up to 136.5% under normal incidence. Selleckchem Perifosine Its absorption bandwidth and absorption peak can be adjusted by changing the conductivity of $\rm VO_2$ or the chemical potential of graphene. The physical mechanism of the absorber is analyzed in detail by the use of the impedance matching theory and the electric field distributions of the $\rm VO_2$ layer and graphene layer. The proposed absorber, with polarization insensitivity and incidence angle of 30° for both TE and TM polarizations, may have potential applications in tunable sensors, modulators, and imaging.Owing to their mighty fitting ability, the supervised learning-based deep-learning (DL) models have been widely used in the area of optical performance monitoring (OPM) to improve the optical monitors' performance. However, the supervised learning-based DL models used in OPM are based on two important premises. The first premise is enough training data with labels; the second premise is the same distribution of the training and test data. Nevertheless, it is hard to meet the two premises in the real-world environment where the optical performance monitors are deployed, since the data are unlabeled and the optical network environment is dynamic (such as component aging caused by slow parameter variation), causing the degradation of the monitoring performance. This is because the supervised learning-based DL models lack the adaptability of the dynamic environment. For the purpose of improving the optical performance monitors' adaptability, we propose a transfer-learning-based convolutional neural network model to maintain the monitoring performance in the dynamic optical network environment. The transfer-learning method can transfer the learned knowledge from the labeled data under an invariant optical network environment to the unlabeled data under a dynamic optical network environment. During the training phase, the maximum mean discrepancy (MMD) is applied to match the features extracted from the source and the target domains. When the trained model is deployed in the OPM monitor, the robustness of the system to the dynamic environment would be enhanced. Four signals (60/100 Gbps 16/64 QAM) under different working environments are used to verify the adaptability of the method. The influence of the MMD's weight rates, batch size, and weight parameters confirmed the effectiveness of our method.Based on the focused optical vortex (OV) generated by a metalens, we studied the physical mechanism for optical manipulation of metal (Ag) nanoparticles in the orbital angular momentum (OAM) field. We found that metal nanoparticles can be stably trapped inside the OV ring and rotated by the azimuthal driving force originating from OAM transfer. The azimuthal force and rotation speed are directly and inversely proportional to the particle size, respectively. The torque for the same particle at the OV ring increases with the increase of the topological charge of the metalens. Considering the same topological charge, the radius of the OV ring or the range of the optical spanner has a positive correlation with the focal length. These kinds of optical tweezers by vortex metalenses can be used as an optical spanner or micro-rotor for lab-on-chip applications.Lithium niobate-on-insulator (LNOI) has been emerging as a popular integration platform for optical communications and microwave photonics. An edge coupler with high coupling efficiency, wide bandwidth, high fabrication and misalignment tolerance, as well as a small footprint is essential to couple light in or out of the LNOI chip. Some edge couplers have been demonstrated to realize fiber-to-chip coupling in the last few years, but the coupling with distributed feedback (DFB) semiconductor laser is rarely studied. In this paper, we propose a multi-tip edge coupler with three tips to reduce the mode size mismatch between the LNOI waveguide and the DFB laser. The tilted sidewall, fabrication tolerance, misalignment tolerance, and facet reflection due to the effective index mismatch are discussed. It shows that the proposed multi-tip edge coupler can be practically used in the production of effective LNOI integrated chips.An optical fiber interferometer coated with PbS quantum dots (QDs) was developed for copper ion ($\rmCu^2 +$) detection. The QDs were modified by a multifunctional copolymer that enabled QD surface ligation, dispersion, and coordination with $\rmCu^2 +$. $\rmCu^2 +$ coordination with the polymer induced changes in the surrounding refractive index of the interferometer. The sensor was highly selective for $\rmCu^2 +$ and showed a linear detection range of 0-1000 µM with a limit of detection of 2.20 µM in both aqueous and biological solutions.In this paper, a cascade double-loop control (DLC) combined with modeling compensation methods is proposed to improve the tracking precision of the multiaperture imaging system (MAIS). The application of the flexible thin-wall ring mechanism in the coupling rotating prism (CRP) system causes a series of tracking and pointing challenges. Disturbances such as friction, shaft deformation, and model perturbation significantly deteriorate the tracking and pointing accuracy of the CRP. Two different modeling compensation methods that are interfaced with classical DLC are proposed to guarantee the tracking precision of the MAIS. Moreover, the disturbance observation and compensation performance of two different modeling compensation methods are analyzed and compared. Finally, simulation and experiment results indicate that the proposed control methods, especially model compensation based on speed close-loop control, obtain the best performance for disturbance rejection in the MAIS.A silicon-based engineered hybrid plasmonic waveguide with ultra-low dispersion is proposed. The ridge-shaped structure of the nanophotonic waveguide enables nano-scale confinement with electrically tunable characteristics using the plasma dispersion effect in silicon. The waveguide exhibits ultra-low dispersion of $1.28\;\rm ps^2/\rm m$ at telecommunication wavelength (1550 nm) in C band together with dual flatband dispersion over a wavelength range of 370 nm. The hybrid plasmonic mode is made to be confined in 15 nm thick $\rm SiO_2$ with a propagation loss of 15.3 dB/mm utilizing the engineered ridge structure comprising Si, $\rm SiO_2$, and gold. In addition, the proposed waveguide shows six zero-dispersion wavelengths. The imaginary and real parts of the effective refractive index of the guided hybrid plasmonic mode are reported to be tunable with the applied voltage. The reported numerical results can pave the way for achieving intensity modulators and other electrically tunable devices at telecommunication wavelengths. The ultra-low dispersion and electrical tuning make this nanophotonic waveguide an absolute contender for applications including efficient nonlinear signal processing such as wide wavelength conversion based on four-wave mixing, supercontinuum generation, and other nanoscale integrated photonic devices.Adaptive optics (AO) compensation for imaging or coherent illumination of a remote object relies on accurate sensing of atmospheric aberrations. When a coherent beacon is projected onto the object to enable wavefront sensing, the reflected reference wave will exhibit random variation in phase and amplitude characteristics of laser speckle. In a Shack-Hartmann wavefront sensor (SHWFS) measurement, speckle effects cause fluctuations in the intensity of focal spots and errors in the position of their centroids relative to those expected from purely atmospheric phase aberrations. The resulting error in wavefront measurements negatively impacts the quality of atmospheric phase conjugation. This paper characterizes the effect of reflected laser speckle on the accuracy of SHWFS measurements for ground-to-space beam projection systems in weak turbulence conditions. We show via simulation that the speckle-induced error in centroiding depends on the ratio between beacon diameter and the diffraction-limited resolution of the lenslet and confirm these results with experimental data. We provide experimental validation that averaging of SHWFS lenslet spot intensities over speckle realizations converges to the incoherent intensity as expected. We further show that the effects of shot noise and speckle noise add in quadrature, simplifying noise analysis. Finally, we characterize the effect of temporal averaging under typical conditions of target motion and integration time. This work provides a straightforward set of relations that can help investigators more accurately estimate the required integration time for wavefront sensing in the presence of laser speckle.White light-emitting diodes (LEDs) are widely used in various lighting fields as a part of energy-efficient technology. However, some shortcomings of luminescent materials for white LEDs, such as complexity of synthesis, high cost, and harmful impact on the environment, limit their practical applications to a large extent. In this respect, the present work aims to study the ability of using Berberine (BBR) chloride extracted from Rhizoma coptidis and Phellodendron Chinese herbs as yellow phosphor for white LEDs. For this, white LEDs were successfully fabricated by applying 0.006 g of BBR chloride onto the blue LED chips (450 nm). The produced LEDs exhibited good luminescence properties at a voltage of 2.4 V along with eco-friendly characteristics and low cost. The Commission International de l'Eclairage chromaticity, the correlated color temperature, and the color rendering index were determined to be ($x = 0.32$, $y = 0.33$), 5934 K, and 74, respectively. Therefore, BBR chloride is a suitable environmentally friendly and easily accessible yellow phosphor for white LEDs.Investigating real-time phenomena in bio-polymers has received much attention because of their increasing demands in polymer substitution. The 3D morphometry of polymer surfaces may be very impactful in such studies. Here, digital holographic microscopy (DHM) is applied for quantitative measurement of the rare morphological changes of UV-A and UV-C exposed nanocomposites during their incubation with excess water. By reconstructing the recorded successive digital holograms, the time evolution of the swelled regions of the samples is derived. Our results clearly show that the higher water swelling of UV-A irradiated starch/kefiran/ZnO may be attributed to its higher hydrophilicity.A novel trench-assisted dual-mode multi-core fiber with large-mode-field-area is proposed. The structure consists of 17 conventional cores and two air holes according to a regular hexagon, which can realize strict dual-mode transmission. The structural parameters' effect on mode transmission characteristics, mode-field-area, and bending loss are analyzed systematically. By optimizing the structural parameters, the mode-field-area of the fundamental mode can reach $2100.619\;\unicodex00B5\rm m^2$. The introduction of the trench with a lower refractive index than cladding can reduce the bending loss to $9.88 \times 10^- 4\;\rm dB/\rm m$ when the bending radius is 2.3 cm. Besides, the structural design is flexible, and the manufacturing process is simple, which has broad application prospects.