Effects of Single Vacancy on Electronic and Optical Properties for γ-Si3N4

The energetics, electronic structures, and optical properties of several neutral vacancies for γ-Si3N4 are studied based on density function theory within the generalized gradient approximation. The binding and formation energies of nitrogen vacancy are smaller than that of silicon vacancies, implying that nitrogen vacancy can be easily formed in γ-Si3N4.Corresponding density of states of different point vacancies is analyzed. We concluded that the neutral silicon vacancies introduce the p-type carriers into the system, whereas single nitrogen vacancy leads to an n-type semiconductor. The results show indirect semiconductor of nitrogen vacancy for γ-Si3N4. The effects of optical properties are discussed on single vacancies for γ-Si3N4. For silicon vacancies, the materials have much higher static dielectric constants than these of nitrogen vacancy and perfect γ-Si3N4. The single nitrogen vacancy for γ-Si3N4 has no effects on absorption and reflection in visible and infrared light. For silicon vacancy, it is significantly increased.

A Fiber Optic Sensor for 2,4-dichlorophenol Analysis based on Optical Composite Oxygen-sensitive Film

A novel fiber optic sensor based on optical composite oxygen-sensitive film was developed for determination of 2,4-dichlorophenol(DCP).The optical composite oxygen-sensitive film consists of tris(2,2’-bipyridyl)dichloro ruthenium(II)hexahydrate(Ru(bpy)3Cl2)as the fluorescence indicator and iron(III)tetrasulfophthalocyanine(Fe(III)PcTs)as bionic enzyme.A lock-in amplifier was used for detecting the lifetime of the composite oxygen-sensitive film by measuring the phase delay of the sensor head.The different variables affecting the sensor performance were evaluated and optimized.Under the optimal conditions(i e,pH 6.0,25℃,Fe(III)PcTs concentration of 5.0×10^-5 mol/L),the linear detection range,detection limit and response time of the fiber optic sensor are 3.0×10^-7-9.0×10^-5 mol/L,4.8×10^-8 mol/L(S/N=3),and 220 s,respectively.The sensor displays high selectivity,good repeatability and stability,which have good potentials in analyzing DCP concentration in practical water samples.

Synthesis of NiMoO_4 nanoparticles by sol-gel method and their structural,morphological,optical,magnetic and photocatlytic properties

Nickel molybdate(NiMoO4)nanoparticles(NPs)were synthesized by sol-gel method.Utilizing water as solvent providescrystalline nanostructures.These nanocrystals were structurally characterized by X-ray diffraction,energy dispersive X-ray analysis(EDX),and Fourier transform infrared spectra.Compositional stoichiometry was confirmed by EDX technique.The size and shapewere observed by scanning electron microscopy(SEM)and transmission electron microscope(TEM).It was found that the obtainedNPs were pure and single phase crystalline with monoclinic structure.The optical properties were studied by ultraviolet-visiblediffuse reflectance spectroscopy(UV-Vis-DRS)and photoluminescence(PL)measurements at room temperature.The magneticproperties were studied by vibrating sample magnetometer(VSM)and results showed superparamagnetic behavior of the obtainednanoparticles.Photocatalytic activity of NiMoO4was studied.The photocatalytic activity of NiMoO4was enhanced with the additionof TiO2.The catalysts NiMoO4,TiO2and NiMoO4-TiO2nanocomposites(NC)were tested for photocatalytic degradation(PCD)of4-chlorophenol(4-CP).It was found that PCD efficiency of NiMoO4-TiO2NC was higher than that of pure NiMoO4and TiO2.

Retrieval of Volcanic Sulfate Aerosols Optical Parameters from AHI Radiometer Data

This paper presents a method for retrieving optical parameters from volcanic sulfate aerosols from the AHI radiometer on board the Himawari-8 satellite.The proposed method is based on optical models for various mixtures of aerosol components from volcanic clouds,including ash particles,ice crystals,water drops,and sulfate aerosol droplets.The application of multi-component optical models of various aerosol compositions allows for the optical thickness and mass loading of sulfate aerosol to be estimated in the sulfuric cloud formed after the Karymsky volcano eruption on 3 November 2021.A comprehensive analysis of the brightness temperatures of the sulfuric cloud in the infrared bands was performed,which revealed that the cloud was composed of a mixture of sulfate aerosol and water droplets.Using models of various aerosol compositions allows for the satellite-based estimation of optical parameters not only for sulfate aerosol but also for the whole aerosol mixture.

六方Al_(4)SiC_(4)弹性性质、电子结构和光学性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理计算方法系统地研究了Al_(4)SiC_(4)的晶体结构、弹性常数、电子结构和光学性质,并对结果进行了理论分析.计算得到的晶格常数和弹性常数均与实验值及其它计算值相符,并说明了六方Al_(4)SiC_(4)的晶体结构是稳定的;计算得到了六方Al_(4)SiC_(4)的体积、剪切、杨氏模量及泊松比与文献值一致,Al_(4)SiC_(4)的禁带宽度为1.076 eV.计算得到了六方Al_(4)SiC_(4)在(100)和(001)方向上的光学响应函数随光子能量的变化关系,包括复介电函数、复折射率、吸收光谱及反射光谱.在(100)和(001)方向上,计算得到其静态介电常数分别为7.74和8.96,折射率分别为2.78和2.99.计算结果可以为相关应用提供理论依据.

First-principles investigation of electronic structure,effective carrier masses, and optical properties of ferromagnetic semiconductor CdCr_2S_4

The electronic structures, the effective masses, and optical properties of spinel CdCr_2S_4 are studied by using the fullpotential linearized augmented planewave method and a modified Becke–Johnson exchange functional within the densityfunctional theory. Most importantly, the effects of the spin–orbit coupling（SOC） on the electronic structures and carrier effective masses are investigated. The calculated band structure shows a direct band gap. The electronic effective mass and the hole effective mass are analytically determined by reproducing the calculated band structures near the BZ center.SOC substantially changes the valence band top and the hole effective masses. In addition, we calculated the corresponding optical properties of the spinel structure CdCr_2S_4. These should be useful to deeply understand spinel CdCr_2S_4 as a ferromagnetic semiconductor for possible semiconductor spintronic applications.

Optical Spectroscopy of Pr3+ Ion Singly Doped LiLuF4 Single Crystal by Bridgman Method

High quality LiLuF4 single crystals doped with various Pr3+ ions were synthesized by a vertical Bridgman method in completely sealed platinum crucibles. The excitation spectra spans from 420 nm to 500 nm. The prepared single crystals exhibit a blue band at 480 nm(3P0→3H4), a green band at 522 nm (3P1→3H5), and a red band at 605 nm (1D2→3H4)when excited at 446 nm;their corresponding average lifetimes are 38.5μs, 37.3μs, and 36.8μs, respectively, which are much longer than those in oxide single crystals. The effects of excitation wavelength and doping concentration on emission intensities and chromaticity coordinates are investigated. The optimal Pr3+ concentration is confirmed to be 0.5%.The temperature dependent emission shows that the emission intensity constantly decreases with the increase of temperature from 298 K to 443 K due to the enhancement of nonradiative quenching at high temperature. The 3P0→3H4 transition is the most vulnerable to temperature, followed by the 3P1→3H5 transition and 1D2→3H4 transition.

Widely Tunable Middle Infrared Optical Parametric Oscillator Pumped by the Q-Switched Ho：GdVO_4 Laser

We demonstrate a middle infrared ZnGeP_2 optical parametric oscillator pumped by the Q-switched Ho：GdVO_4 laser. When the incident Ho pump power is 4.12 W, the maximum average output power of the ZGP-OPO laser is 2.05 W, corresponding to a slope efficiency of 74.6%. The ZGP-OPO laser produces 4.2 ns mid-infrared pulses at a pulse repetition rate of 5 kHz. In addition, we obtain 0.8 um of tunable range for the signal wave and 2.1 um of tunable range for the idler wave.

First principles study on electronic structure and optical properties of novel Na-hP4 high pressure phase

The electronic structure and optical properties of novel Na-hP4 high pressure phase at different pressures(260,320,400 and 600 GPa)were investigated by the density functional theory(DFT)with the generalized gradient approximation(GGA)for the exchange and correlation energy.The band structure along the higher symmetry axes in the Brillouin zone,the density of states(DOS) and the partial density of states(PDOS)were presented.The band gap increases and the energy band expands to some extent with the pressure increasing.The dielectric function,reflectivity,energy-loss function,optical absorption coefficient,optical conductivity, refractive index and extinction coefficient were calculated for discussing the optical properties of Na-hP4 high pressure phase at different pressures.

Effect of Oxygen Concentration and Annealing Theatment on the Optical Properties of the Transparent Conductive CdIn_2O_4 Thin Films

Transparent conductive cadmium indium oxide films (CdIn2O4) were prepared by r.f. reactive sputtering from Cd-In alloy targets under an Ar-O2 atmosphere. Electrical conductivity of the order of 105Ω-1.m-1 and the optical transmission as high as 94% are easily attained by postdeposition annealing treatment. The effects of oxygen concentration in the reactive gas mixture and post-deposition annealing treatment on the optical transmittance as well as optical parameters, such as refractive index (n), extinction coefficient (k), real part (ε') and imaginary part (ε') of the dielectric constant, were studied in the visible and near-infrared region. The highfrequency dielectric constant ε∞ the plasma frequency ωP, and the conduction band effective mass mc of different samples were also investigated

Geant4 Comparative Study of Affecting Different Parameters on Optical Photons Related to the Plastic Scintillation Detector

In this research, different parameters of plastic scintillator detector were investigated by Geant4 simulation toolkit. These parameters consisted of radius, length and position of PMT as well as surface reflective type and finish options. Furthermore, response time distributions of two organic plastic materials were studied. The results indicated that collecting optical photons has a linear relationship with PMT radius head. Also, the vertical location of PMT has a non-linear relationship with the optical photons collection. However, the collection decreased by increasing PMT length or moving PMT head horizontal position. The response functions of two plastic scintillator materials were in good agreement with experimental published results. Also, Geant4 radiation transport code can simulate incident radiation photon and predict subsequent events to the PMT head very well. The results indicated that BC-404 has faster scintillation properties versus BC-400 organic scintillator materials. Comparison between Geant4 outputs illustrates that the best reflector material and surface finish type for optical photons is ground TiO2.

A cloud optical and microphysical property product for the advanced geosynchronous radiation imager onboard China's Fengyun-4 satellites: The first version

风云四号作为中国新一代静止气象卫星,提供了高时空分辨率的监测产品。本文介绍风云四号搭载的先进地球同步轨道辐射成像仪AGRI的云光学和微物理特性产品.该产品包含了基于双光谱通道反演的云光学厚度和云粒子有效半径产品,以及基于机器学习的云识别和云相态产品。与时空匹配的主动卫星观测结果对比显示,该产品的云识别和云相态的准确率分别在95%和85%;该产品提供的云光学厚度和云有效粒径与经典的MODIS产品的相关系数达到0.76和0.63.团队将持续优化和更新该云光学和微物理特性定量产品,服务风云四号卫星定量应用。

First-principles study of structure and nonlinear optical properties of CdHg(SCN)_4 crystal

The geometric structure,electronic structure,and optical properties of CdHg（SCN）4 crystal are calculated by using the density functional perturbation theory and Green function screening Coulomb interaction approximation.The band gap of CdHg（SCN）4 crystal is calculated to be 3.198 eV,which is in good agreement with the experimental value 3.265 eV.The calculated second-order nonlinear optical coefficients are d14 = 1.2906 pm/V and d15 = 5.0928 pm/V,which are in agreement with the experimental results（d14=（1.4 ±0.6） pm/V and d15=（6.0 ±0.9） pm/V）.Moreover,it is found that the contribution to the valence band mainly comes from Cd-4d,Hg-5d states,and the contributions to the valence band top and the conduction band bottom predominantly come from C-2p,N-2p,and S-3p states.The second-order nonlinear optical effect of CdHg（SCN）_4 crystal results mainly from the internal electronic transition of（SCN）^-.

EFFECT OF THE DEFECT STATES DENSITY ON OPTICAL BAND GAP OF CdIn_(2)O_(4)THIN FILM

Transparent conducting oxides CdIn2O4 thin films were prepared by radio-frequenc y reactive sputtering from a Cd-In alloy target in Ar+O2 atmosphere. By transmis sion spectrum and Hall measurement for different samples prepared at different s ubstrate temperatures, it could be found that the carrier concentration would in crease with the decrease of substrate temperature, but absorption edge showed an abrupt variation from a blue shift to a red shift. Theoretically, the paper for mulated the effect of high-density point defects on band structures; it embodied the formation of band tailing, Burstein-Moss shift and band-gap narrowing. The density of holes will influence the magnitude of optical band gap and transmitta nce of light. Since extrapolation method does not fit degenerate semiconductor m aterials, a more accurate method of obtaining optical band gap is curve fitting. In addition, ionized impurities scattering is the main damping mechanism of the free electrons in CdIn2O4 films, the density of ionized impurities induced by a ltering substrate temperature will affect the carriers mobility.

First-principles study of the optical properties of defect electronic structure and chalcopyrite CdGa2Te4

The electronic and optical properties of the defect chalcopyrite CdGa2Te4 compound are studied based on the first- principles calculations. The band structure and density of states are calculated to discuss the electronic properties and orbital hybridized properties of the compound. The optical properties, including complex dielectric function, absorption coefficient, refractive index, reflectivity, and loss function, and the origin of spectral peaks are analysed based on the electronic structures. The presented results exhibit isotropic behaviours in a low and a high energy range and an anisotropic behaviour in an intermediate energy range.

Exploration of structural,optical,and photoluminescent properties of (1-x)NiCo_(2)O_(4)/xPbS nanocomposites for optoelectronic applications

The(1-x)NiCo_(2)O_(4)/x PbS(0≤x≤0.2)nanocomposite samples are synthesized using the hydrothermal and thermolysis procedures.The different phases developed in the obtained nanocomposite samples are accurately determined using the x-ray diffraction technique equipped with a line-detector.The percentage of the formed phases(NiCo_(2)O_(4)(NCO),PbS,PbSO_(4)),structural and microstructure parameters are determined using Rietveld quantitative phase analysis.The transmission electron microscope(TEM)images and Rietveld analysis reveal almost isotropic particle size in the nano range with a very narrow size distribution.The obtained phase percentage of PbS and PbSO4are smaller than nominated values(x)suggesting dissolving of some Pb and S ions into NCO which is then confirmed by the analysis of Fourier-transform infrared(FTIR)spectra of nanocomposite samples.The absorption spectra are modified upon doping NCO with PbS.The optical band gaps of the nanocomposites increase as the amount of PbS augments.The effect of alloying on extinction coefficient,refractive index,dielectric constant,optical conductivity,the intensity,and emitted color from the photoluminescence of the nanocomposite samples are also studied.The refractive index value of NCO and NCO-PbS nanocomposite samples exhibit normal dispersions.The photoluminescent measurements reveal that the NCO-PbS nanocomposites can emit a violet color.The improvement in the values of the nonlinear optical(NLO)parameters of pristine NCO at high frequencies or the nanocomposite samples at low frequencies,are made them used in NLO photonic devices.

Optical and atomic force microscopic study on step bunching in BaB_2O_4 crystal growth

The formation of macrostep during high-temperature phase of barium meta-borate （^-BaB204） single crystal growth has been investigated by both optical in-situ observation system and atomic force microscopy （AFM）. The in- si$u observation results demonstrate that the critical linear size of growing facet exceeding the size that the macrostep generates is significantly anisotropic. The critical linear sizes are around 280 ~m and 620 ~m for {1010} and （T010} planes, respectively. AFM study illustrates that macrostep train with a height of 150 nm^200 nm is one typical morphological feature of the as-grown crystal surface. The riser of each macrostep consists of several straight and parallel sub-steps, indicating the occurrence of step bunching. Additionally, triangular sub-steps with heights of several nanometers on the treads of the macrosteps are found to be another typical feature of surface morphology, which implies a microscopically competitive bunching of sub-steps between various crystallographic orientations.

ELECTROCHEMICAL AND OPTICAL STUDY ON C_(60) FILM IN LiClO_4 POLYPROPYENE CARBONATE (PC) SOLUTION

For the first time we observed the electrochromism of C_(60) film intercalated by lithium and obtained some amount of intercalate Li_3C_(60) with cyclic voltammetry. The optical absorption properties of this intercalate have been studied.

Nonlinear Optical Properties and Optical Limiting Measurements of {(1Z)-[4-(Dimethylamino)Phenyl]Methylene} 4-Nitrobenzocarboxy Hydrazone Monohydrate under CW Laser Regime

We report results from the investigation of the nonlinear refractive index and nonlinear absorption coefficient of {(1Z)-[4-(Dimethylamino)phenyl]methylene} 4-nitrobenzocarboxy hydrazone mono-hydrate (DMPM4NBCHM) solution using Z-scan technique with a continuous wave (CW) Argon ion laser. The results show that this type of organic material has a large nonlinear absorption and nonlinear refractive index at 488 nm and 514 nm. The origin of the nonlinear effects was discussed. We demonstrate that the light induced nonlinear refractive index variation, leads to limiting effect. The results indicated that DMPM4NBCHM could be promising candidates for application on nonlinear photonic devices and optical limiters.

MICROSTRUCTURES AND OPTICAL PROPERTIES OF Te_（81）Ge_（15）Sb_4 THIN FILMS USED FOR PHASE CHANGE RECORDING MATERIALS

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