First-Principles Study of Structural Stabilities, Electronic and Optical Properties of SrF2 under High Pressure

An investigation of structural stabilities, electronic and optical properties of SrF2 under high pressure is conducted using a first-principles calculation based on density functional theory （DFT） with the plane wave basis set as implemented in the CASTEP code. Our results predict that the second high-pressure phase of SrF2 is of a Ni2In- type structure, and demonstrate that the sequence of the pressure-induced phase transition of SrF2 is the fluorite structure （Fm3m） to the PbC12-type structure （Pnma）, and to the Ni2In-type phase （P63/mmc）. The first and second phase transition pressures are 5. 77 and 45.58 GPa, respectively. The energy gap increases initially with pressure in the Fm3m, and begins to decrease in the Pnma phases at 30 GPa. The band gap overlap metallization does not occur up to 210 GPa. The pressure effect on the optical properties is discussed.

Effects of Annealing Temperature on Structural and Optical Properties of ZnO Thin Films

The effects of annealing temperature on the structural and optical properties of ZnO films grown on Si （100） substrates by sol-gel spin-coating are investigated. The structural and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectra. X-ray diffraction analysis shows the crystal quality of ZnO films becomes better after annealing at high temperature. The grain size increases with the temperature increasing. It is found that the tensile stress in the plane of ZnO films first increases and then decreases with the annealing temperature increasing, reaching the maximum value of 1.8 GPa at 700℃. PL spectra of ZnO films annealed at various temperatures consists of a near band edge emission around 380 nm and visible emissions due to the electronic defects, which are related to deep level emissions, such as oxide antisite （OZn）, interstitial oxygen （Oi）, interstitial zinc （Zni） and zinc vacancy （VZn^-）, which are generated during annealing process. The evolution of defects is analyzed by PL spectra based on the energy of the electronic transitions.

Structured Illumination Chip Based on Integrated Optics

A compact structured illumination chip based on integrated optics is proposed and fabricated on a silicon-on- insulator platform. Based on the simulation of Caussian beam interference, we adopt a chirped diffraction grating to achieve a specific interference pattern. The experimental results match well with the simulations. The portability and flexibility of the structured illumination chip can be increased greatly through horizontal encapsulation. High levels of integration, compared with the conventional structured illumination approach, make this chip very compact, with a footprint of only around 1 mm2. The chip has no optical lenses and can be easily combined with a microfluidic system. These properties would make the chip very suitable for portable 3D scanner and compact super-resolution microscopy applications.

Integrated structured light manipulation

Structured light,also known as tailored light,shaped light,sculpted light,or custom light,refers to a series of special light beams with spatially variant amplitudes and phases,polarization distributions,or more general spatiotemporal profiles.In the past decades,structured light featuring distinct properties and unique spatial or spatiotemporal structures has grown into a significant research field and given rise to many developments from fundamentals to applications.Very recently,integrated structured light manipulation has become an important trend in the frontier of light field manipulation and attracted increasing interest as a highly promising technique for shaping structured light in an integrated,compact,and miniaturized manner.In this article,we give a comprehensive overview of recent advances in integrated structured light manipulation(generation,processing,detection,and application).After briefly introducing the basic concept and development history of structured light,we present representative works in four important aspects of integrated structured light manipulation,including multiple types of integrated structured light generation,many sorts of integrated structured light processing,diverse forms of integrated structured light detection,and various kinds of integrated structured light applications.We focus on summarizing the progress of integrated structured light manipulation from basic theories to cutting-edge technologies,to key devices,and to a wide variety of applications,from orbital angular momentum carrying light beams to more general structured light beams,from passive to active integration platforms,from micro-nano structures and metasurfaces to 2D photonic integrated circuits and 3D photonic chips,from in-plane to out-of-plane,from multiplexing to transformation,from linear to nonlinear,from classical to quantum,from optical communications to optical holography,imaging,microscopy,trapping,tweezers,metrology,etc.Finally,we also discuss in detail the future trends,opportunities,challenges,and solutions,and give a vision for integrated structured light manipulation.

Design and Fabrication of an Er-Doped Silica Optical Fiber with Six Photosensitive Subcores

A type of multi-core Er-doped photosensitive silica optical fiber （MC-EDPF） is proposed and fabricated, in which a high consistency Er-doped core is surrounded by six high consistency Ge-doped cores. The multi-core design can overcome the difficulties encountered in the design and fabrication of single-core EDPFs through a modified chemical vapor deposition method combined with solution doping technology, and there is a conflict between high consistency Er doping and high consistency Ce doping. The absorption of MC-EDPFs achieved 15.876dB/m at 1550mm and lOdB/m at 98Ohm. The refleetivity of the fiber Bragg gratings （FBCs） written directly on the MC-EDPFs is as much as 96.84%.

KBa2(PO3)5： Properties and Comparison with Isostructural Polyphosphate Compounds

A noncentrosymmetric polyphosphate compound, KBa2（PO3）5, 1 was prepared and characterized. It features 1D [PO3]∞ chains of condensed [PO4]^（3-） tetrahedral units. The polycrystalline sample of 1 exhibits second harmonic generation（SHG） response, demonstrating that the activity of the title compound is about 0.6 times that of KDP that is comparable to the isostructural RbBa2（PO3）5（2） and KPb2（PO3）5（3）. Additionally, powder X-ray diffraction（PXRD）, thermal analysis, IR spectroscopy, UV-Vis-near-IR diffuse reflectance spectroscopy, and theoretical calculations have been also studied, and the structure and property comparison among this type of polyphosphates are summarized.

Simple Raman scattering sensor integrated with a metallic planar optical waveguide: effective modulation via minor structural adjustment

We report experimental realization of Raman spectra enhancement of copper phthalocyanine, using an on-chip metallic planar waveguide of the sub-millimeter scale. The oscillating ultrahigh order modes excited by the direct coupling method yield high optical intensity at resonance, which is different from the conventional strategy to create localized ＂hot spots.＂ The observed excitation efficiency of the Raman signal is significantly enhanced,owing to the high Q factor of the resonant cavity. Furthermore, effective modulation of the Raman intensity is available by adjusting the polymethyl methacrylate（PMMA） thickness in the guiding layer, i.e., by tuning the light–matter interaction length. A large modulation depth is verified through the fact that 10 times variation in the enhancement factor is observed in the experiment as the PMMA thickness varies from 7 to 23 μm.

Nonlinear Optical Properties and Ultrafast Dynamics of Undoped and Doped Bulk SiC

Ultrafast third-order nonlinear optical response of bulk 6H-SiC undoped and doped with different nitrogen concentrations are investigated utilizing femtosecond Z-scan and optical Kerr effect （OKE） techniques at the wavelength of 800hm. The Z-scan measurement shows that the third-order nonlinear optical susceptibilities of the doped samples are improved in comparison to the intrinsic sample. The OKE results additionally reveal that the instantaneous nonlinear optical response of the samples can be ascribed to the distortion of the electron cloud. The ultrafast transient spectroscopic measurements with the one-color and two-color pump-probe techniques demonstrate that the ultrafast recovery process in subpicosecond domain is induced by two-photon absorption process, while the slow relaxation component reflects the carrier dynamics of the excited electrons.

First-Principles Study of Electronic and Optical Properties of Y1-xCaxTiO3 （x=0, 0.25, 0.5, 0.75）

The full potential linearized augmented plane wave （FP-LAPW） method with the generalized gradient approximation （GGA） is applied to study the electronic and optical properties of perovskite-type compounds Y1-xCaxTiO3. The lattice parameters, magnetic moment, band structure, density of states and optical conductivity are obtained. The results show that the Ca ion plays an important role in the electronic properties and optical responses. Moreover, the optical properties including the dielectric function, absorption spectrum, extinction coefficient, energy-loss spectrum and refractive index are also discussed.

Effect of Temperature on Structural and Magnetic Properties of Laser Ablated Iron Oxide Deposited on Si（100）

We fabricate Fe3O4 thin films on Si（100） substrates at different temperatures using pulsed laser deposition, and study the effect of annealing and deposition temperature on the structural and magnetic properties of Fe3O4 thin films. Subsequently, the films are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM） and vibrating sample magnetometery （VSM）. The XRD results of these films confirm the presence of the Fe3O4 phase and show room-temperature ferromagnetism, as observed with VSM. We demonstrate the optimized deposition and annealing conditions for an enhanced magnetization of 854 emu/cm3 that is very high when compared to the bulk sample.

Structural and Magnetic Properties of Sm Implanted GaN

The structural and magnetic properties of Sm ion-implanted GaN with different Sm concentrations are investigated. XRD results do not show any peaks associated with second phase formation. Magnetic investigations performed by superconducting quantum interference device reveal ferromagnetic behavior with an ordering tem- perature above room temperature in all the implanted samples, while the effective magnetic moment per Sin obtained from saturation magnetization gives a much higher value than the atomic moment of Sm. These results could be explained by the phenomenological model proposed by Dhar et al. [Phys. Rev. Lett. 94（2005）037205, Phys. Rev. B 72（2005）245203] in terms of a long-range spin polarization of the GaN matrix by the Sm atoms.

Evolution of Structural and Magnetic Properties of BaFe12O19 with B2O3 Addition

We investigate the effects of B2O3 addition on structural and magnetic properties of hard magnetic BaFe12O19 particles. The conventional solid state reaction method is used as the synthesis route. Single phase BaFe12O19 could be synthesized with very small amounts of B2O3 addition and with calcination at low temperatures （850°C） in short times （1 h）. B2O3 addition also improves the magnetic parameters significantly. Remanence magnetization and specific magnetization at 1.5 T increase by ～40% in magnitude although no significant variations on coercivity is observed.

First-Principles Investigations of the Phase Transition and Optical Properties of Solid Oxygen

Using density-functional-theory calculations, a monoclinic metallic post-ζ phase （space group C2/c） is predicted at 215 GPa. The calculated phonon dispersion curves suggest that this structure is stable at least up to 310 GPa. Oxygen remains a molecular crystal and there is no dissociation in the related pressure range. Moreover, it is found that the phase transition from （ to post-ζ phase is attributed to phonon softening, The significant change in the optical properties can be used to identify the phase transition.

星冕仪模块光机热集成仿真分析与试验研究

针对巡天望远镜星冕仪模块光机系统进行集成仿真分析和试验研究,首先根据星冕仪模块热边界仿真分析光机系统热温度场分布;其次,将热温度场映射到光机系统中,利用有限元方法分析在此温度场映射下镜面形变;再次,提取各镜面节点数据拟合镜面的刚体平移量和Zernike多项式系数,分别导入Zemax光学方案,分析温度场对光学系统影响,从而实现光机热集成仿真分析的完整过程;最后,通过试验研究最终方案在主动热控方案下光学性能。集成仿真结果显示,在主动温控载荷条件下,其波前畸变RMS值变化小于千分之一;试验测试结果显示,其波前畸变RMS值为1/25波长,满足指标优于1/20波长的设计要求。

大口径空间光学望远镜桁架结构关键技术研究进展

近年来大口径空间光学望远镜以高像质、宽波段、大幅宽等特点,在开展空间科学探索、精细化对地观测等方面越来越重要。大口径望远镜的主承力结构、大型光学组件的支撑结构往往采用桁架结构,本文围绕实现桁架结构的超轻、超稳特性,从构型优化设计、新型材料、先进制造工艺、精确测量标定方法等方面,系统性梳理了其理论基础、研究方法、应用现状等,并探讨了空间桁架结构技术的发展趋势。

基于笼屉结构的机载高能激光系统光学中舱温度适应性研究

相较于车载、舰载设备,机载设备受体积及工作环境的限制,发展较为缓慢。针对机载设备的轻小型化要求,系统采用“光路堆叠”思想,提出笼屉式分层结构,实现了系统体积的要求。因光学中舱中包含精跟踪及主激光支路,温度变化时各支路间的光轴一致性难以保证,导致跟踪目标发生偏移,主激光支路无法对目标进行精确打击,严重影响系统的工作。为解决上述问题,对光学中舱进行有限元仿真分析,研究光学中舱在20±5℃情况下各镜片的变形。对镜片变形中影响光轴偏折的刚体位移进行提取计算,计算出单个镜片的偏转角度。根据反射棱镜安装误差理论对各支路间的光轴偏移量进行计算,分析精跟踪支路与主激光支路光轴一致性偏差。经过仿真分析,系统精跟踪支路与主激光支路光轴方位偏差为109.634μrad,俯仰偏差为132.952μrad。在实验室中进行25℃温度实验,结果表明,系统精跟踪支路与主激光支路光轴方位偏差为104.019μrad,俯仰偏差为125.009μrad,与仿真结果误差分别为5.40%、6.35%,验证了仿真结果的合理性。

多物理场耦合下FCM堆内行为研究

为研究全陶瓷包覆弥散燃料(FCM)堆内行为,评价FCM芯块的安全性能,优化FCM芯块结构设计,本文采用二维特征模型模拟FCM芯块的热-力学行为,通过计算不同位置TRISO颗粒的内压,作为输入条件,模拟缓冲层的变形将核芯和缓冲层去除,解决了多颗粒映射的难题。通过调整FCM结构参数,计算了不同结构对FCM芯块性能的影响,实现了FCM芯块的结构优化。研究结果表明,在压水堆环境下,FCM芯块中基体最高温度随运行时间迅速增大,在100天左右时温度达到稳定最高温度约为1390K,低于SiC分解温度。SiC基体的环向应力较高,最高可达1200 MPa,远高于SiC的断裂强度,因此基体在运行过程中开概率率较大。TRISO颗粒中SiC层的环向应力较小,最大应力约为180 MPa,具有较低的失效概率(9×10^(-5)),保证了SiC层的结构完整性。此外,当无燃料区尺寸为400μm时,SiC层的失效概率约为2.0×10^(-5),保证了SiC层的完整性。因此,本研究建立的FCM芯块分析方法,为FCM芯块的工程应用和结构优化奠定了基础。

Effect of Co doping on structural, optical, electrical and thermal properties of nanostructured ZnO thin films

Nanocrystalline Zn1-x CoxO（where x varies from 0 to 0.04 in steps of 0.01） thin films were deposited onto glass substrate by the spray pyrolysis technique at a substrate temperature of 350 ℃. The X-ray diffraction patterns confirm the formation of hexagonal wurtzite structure. The crystal grain size of these films was found to be in the range of 11–36 nm. The scanning electron micrographs show a highly crystalline nanostructure with different morphologies including rope-like morphology for undoped ZnO and nanowalls and semispherical morphology for Co-doped Zn O. The transmittance increases with increasing Co^2＋ doping. The optical absorption edge is observed in the transmittance spectra from 530 to 692 nm, which is due to the Co2C absorption bands corresponding to intraionic d–d^＊ shifts. The direct and indirect optical band gap energies decrease from 3.05 to 2.75 eV and 3.18 to 3.00 eV, respectively for 4 mol% Co doping. The electrical conductivity increases with increasing both the Co doping and temperature, indicating the semiconducting nature of these films. The temperature dependence thermal electromotive force measurement indicates that both undoped and Co-doped ZnO thin films show p-type semiconducting behavior near room temperature. This behavior dies out beyond 313 K and they become n-type semiconductors.

热像仪的光轴热稳定性仿真及拓扑优化研究

热成像仪由于工作环境较为恶劣,且自身发热量较大,容易导致热像仪光轴发生热偏移,严重影响其瞄准性能。为了提高红外热像仪的光轴热稳定性,以某型热像仪光轴敏感部件——折转镜为主要研究对象,研究其在不同环境温度条件下的光轴变化情况,并通过构建折转镜的有限元仿真模型以及试验测试系统,获得与试验数据一致性较好的有限元模型;以此为基础,采用基于变密度法的拓扑优化仿真技术,以刚度最大化为设计目标,以体积分数为约束,对折转镜座进行了拓扑优化设计。通过试验测试得出,优化设计的折转镜座的光轴高温偏移量由46.1″减小到25.5″,减小了44.7%,折转镜座的光轴低温偏移量由92.9″减小到51.0″,减小了45.1%,极大地提高了折转镜的光轴热稳定性。最后,将优化后的折转镜安装到某型热像仪中进行整机试验测试,热像仪整机的高温光轴偏移量由0.461 mrad减小到0.340 mrad,下降了26.2%,低温光轴偏移量由0.485 mrad减小到0.296 mrad,下降了39.0%,证明了仿真与拓扑优化模型的可行性与有效性,为后续红外热像仪整机的轻量化设计与性能提升奠定了基础。

Synthesis,structural study,thermal,optical properties and characterization of the new compound[C6H7N2O2]3TeCl5·2Cl

The new organic-inorganic compound, [C_6H_7N_2O_2]_3TeCl_5·2Cl was synthesized and its structure was determined at room temperature in the triclinic system （P^-1） with the following parameters： a = 10.5330（11） ？, b = 10.6663（11） ？, c = 15.9751（16）？, α = 82.090（2）°, β = 71.193（2）°, γ = 68.284（2）°and Z = 2. The final cycle of refinement led to R = 0.057 and Rw = 0.149. The crystal structure was stabilized by an extensive network of N--H···Cl and non-classical C--H···Cl hydrogen bonds between the cation and the anionic group. Several thermal analysis techniques such as thermogravimetric analysis, differential scanning calorimetric analysis and evolved gas analysis were used. We used isoconversional kinetics methods to determine the kinetics parameters. We observe that the decomposition of [C_6H_7N_2O_2]_3TeCl_5·2Cl entails the formation hydrochloric acid of nitroaniline as volatiles. The infrared spectra were recorded in the4000–400 cm^（-1）frequency region. The Raman spectra were recorded in the external region of the anionic sublattice vibration 50–1500 cm^（-1）. The optical band gap was calculated from the UV-Vis absorbance spectra using classical Tauc relation which was found to be 3.12 and 3.67 eV.