Notes

PTENα accounts for safety involving mind towards oxidative strain through getting older.
The finite-difference time-domain (FDTD) method is considered to be one of the most accurate and common methods for the simulation of optical devices. However, the conventional FDTD method is subject to the Courant-Friedrich-Levy condition, resulting in extremely low efficiency for calculating two-dimensional materials (2DMs). Recent researches on the hybrid implicit-explicit FDTD (HIE-FDTD) method show that the method can efficiently simulate homogeneous and isotropic 2DMs such as graphene sheet; however, it is inapplicable to the anisotropic medium. In this paper, we propose an in-plane anisotropic HIE-FDTD method to simulate optical devices containing graphene and black phosphorus (BP) sheets. Numerical analysis shows that the proposed method is accurate and efficient. With this method, we present a novel multi-layer graphene-BP-based dual-band anisotropic terahertz absorption structure (GBP-DATAS) and analyze its optical characteristics. Combining the advantages of graphene and BP localized surface plasmons, the GBP-DATAS demonstrates strong anisotropic plasmonic resonance and high absorption rate in the terahertz band.A single pulse diffraction method to probe the plasma column evolution of the air ionization induced by the femtosecond laser pulse has been proposed. By utilizing a linearly chirped pulse as the probe light, the spatiotemporal evolution spectrum of the plasma column can be acquired in a single measurement. A method based on the Fresnel diffraction integral is proposed to extract the evolution of the phase shift after the probe light is crossing through the plasma column. Results show that the plasma expands rapidly within 7 ps due to the ionization, and then reaches a steady state with a diameter of about 80 μm with the pump pulse energy of 1 mJ. Furtherly, the temporal profile of the free electron density and the refractive index in the plasma region were determined using the corresponding physical models. The single-shot method can be expected to broaden the way for detecting the dynamics of the femtosecond laser-induced plasma.Strong anisotropy of photoluminescence of a (100)-cut β-Ga2O3 and a Mg-doped β-Ga2O3 single crystals was found in UV and visible spectral range, the bands of which were attributed to different types of transitions in the samples. read more Green photoluminescence in the Mg-doped sample was enhanced approximately twice. A remarkable enhancement of two-photon absorption and self-focusing in β-Ga2O3 after doping was revealed by 340-fs laser Z-scanning at 515 nm. The absolute value of complex third order susceptibility χ(3) determined from the study increases by 19 times in [001] lattice direction. Saturable absorption and associated self-defocusing were found in the undoped crystal in the [010] direction, which was explained by the anisotropic excitation of F-centers on intrinsic oxygen defects. This effect falls out of resonance in the Mg-doped crystal. The χ(3) values which are provided by a decrease of bandgap in Mg-doped β-Ga2O3 are χ(3) [001] = 1.85·10-12 esu and χ(3) [010]=χ(3)yyyy = 0.92·10-12 esu. Our result is only one order of magnitude lower than the best characteristic in green demonstrated by a Mg-doped GaN, which encourages subsequent development of Mg-doped β-Ga2O3 as an effective nonlinear optical material in this region.Metal nanorod arrays exhibit hyperbolic dispersion and optical nonlocality under certain conditions. Therefore, their optical behaviors can hardly be expressed by incident-angle-independent effective permittivity. Here we extract effective permittivity of silver nanorod arrays with diameters of 4 nm, 12 nm, and 20 nm by polarized transmission method in the visible range. The incident angles are chosen from 20° to 60° to study the influence of optical nonlocality on permittivity. We demonstrate how the diameter of the nanorods can control the effective permittivity beyond the effective medium theory. The results suggest that the effective permittivity gradually loses its accuracy as the diameter increases due to the optical nonlocality. Our experiment verifies that ultrathin nanorod arrays can resist the fluctuations caused by changes in incident angle. We also extract k-dependent effective permittivity of nanorods with larger diameters.Lithium niobate on insulator (LNOI) waveguides, as an emerging technology, have proven to offer a promising platform for integrated optics, due to their strong optical confinement comparable to silicon on insulator (SOI) waveguides, while possessing the versatile properties of lithium niobate, such as high electro-optic coefficients. In this paper, we show that mode hybridization, a phenomenon widely found in vertically asymmetric waveguides, can be efficiently modulated in an LNOI ridge waveguide by electro-optic effect, leading to a polarization mode converter with 97% efficiency. link2 Moreover, the proposed device does not require tapering or periodic poling, thereby greatly simplifying the fabrication process. It can also be actively switched by external fields. Such a platform facilitates technological progress of photonics circuits and sensors.In this study, we employ our developed instrument to obtain high-throughput multi-angle single-particle polarization scattering signals. Based on experimental results of a variety of samples with different chemical composition, particle size, morphology, and microstructure, we trained a deep convolutional network to identify the polarization signal characteristics during aerosol scattering processes, and then investigate the feasibility of multi-dimensional polarization characterization applied in the online and real-time fine and accurate aerosol recognition. Our model shows a high classification accuracy rate (>98%) and can achieve aerosol recognition at a very low proportion ( less then 0.1%), and shows well generalization ability in the test set and the sample types not included in the training set. The above results indicate that that the time series pulses from multi-angle polarization scattering contain enough information related with microscopic characteristics of an individual particle, and the deep learning model shows its capability to extract features from these synchronous multi-dimensional polarization signals. Our investigations confirm a good prospect of aerosol attribute retrieval and identifying and classifying individual aerosols one by one by the combination of multi-dimensional polarization scattering indexes with deep learning method.The coherent Ising machine (CIM) implemented by degenerate optical parametric oscillator (DOPO) networks is a novel optical platform to accelerate computation of hard combinatorial optimization problems. Nevertheless, with the increase of the problem size, the probability of the machine being trapped by local minima increases exponentially. According to the quantum adiabatic theorem, a physical system will remain in its instantaneous ground state if the time-dependent Hamiltonian varies slowly enough. Here, we propose a method to help the machine partially avoid getting stuck in local minima by introducing quantum adiabatic evolution to the ground-state-search process of the CIM, which we call A-CIM. Numerical simulation results demonstrate that A-CIM can obtain improved solution accuracy in solving MAXCUT problems of vertices ranging from 10 to 2000 than CIM. The proposed machine that is based on quantum adiabatic theorem is expected to solve optimization problems more correctly.A high-resolution and large-dynamic-range temperature sensor adopting a pair of fiber Bragg grating as Fabry-Pérot cavity (FBG-FP) and laser frequency dither locking method is proposed and experimentally demonstrated. This sensor exhibits a temperature resolution of 7×10-4 °C and a dynamic range of ∼46 °C. It is especially useful for applications where very small temperature changes need to be detected, such as deep ocean temperature measurement.We study the polarization dynamics of ultrafast solitons in mode-locked fiber lasers. We find that when a stable soliton is generated, its state of polarization shifts toward a stable state, and when the soliton is generated with excess power levels it experiences relaxation oscillations in its intensity and timing. link3 On the other hand, when a soliton is generated in an unstable state of polarization, it either decays in intensity until it disappears, or its temporal width decreases until it explodes into several solitons, and then it disappears. We also found that when two solitons are simultaneously generated close to each other, they attract each other until they collide and merge into a single soliton. Although these two solitons are generated with different states-of-polarization, they shift their state of polarization closer to each other until the polarization coincides when they collide. We support our findings by numerical calculations of a non-Lagrangian approach by simulating the Ginzburg-Landau equation governing the dynamics of solitons in a laser cavity. Our model also predicts the relaxation oscillations of stable solitons and the two types of unstable solitons observed in the experimental measurements.We propose a microring resonator (MRR) optical switch based on III-V/Si hybrid metal-oxide-semiconductor (MOS) optical phase shifter with an ultrathin InP membrane. By reducing the thickness of the InP membrane, we can reduce the insertion loss of the phase shifter, resulting in a high-quality-factor (Q-factor) MRR switch. By optimizing the device structure using numerical analysis, we successfully demonstrated a proof-of-concept MRR optical switch. The optical switch exhibits 0.3 pW power consumption for switching, applicable to power-efficient, thermal-crosstalk-free, Si programmable photonic integrated circuits (PICs) based on wavelength division multiplexing (WDM).It is difficult to collect the crack propagation signal under general continuous welding condition due to other signal interference of molten pool. In order to study the effect of residual stress on crack propagation, acoustic emission technology was successfully applied to monitor welding process according to the characteristics of pulsed laser welding. Crack free welding is achieved by reducing the pulse interval to limited the crack size of single pulse welding spot. The welding process was monitored synchronously by high speed photography and acoustic emission, the evidence of crack propagation after solidification of weld is successfully captured.The laser-plasma interactions that occur during the ablation of solid materials by a femtosecond filament superimposed with a lower-intensity nanosecond pulse are investigated. Pulses of 50 fs duration with intensities of ∼1014 W/cm2 centered at 800 nm are combined with 8 ns pulses at 1064 nm with ∼1010 W/cm2 intensity with delays of ±40 ns on crystalline GaAs targets in air. For each delay, the volume of material removed by a single femtosecond-nanosecond dual-pulse is compared to the laser-plasma interactions that are captured with ultrafast shadowgraph imaging of the plasma and shockwave generated by each pulse. Sedov-Taylor analysis of the shockwaves provides insight on the coupling of energy from the second pulse to the plasma. These dynamics are corroborated with radiation-hydrodynamics simulations. The interaction of the secondary pulse with the pre-existent plasma is shown to play a critical role in enhancing the material removal.
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