Particle erosion of infrared materials

Erosion test of some infrared （IR） optical crystals （Ge, ZnS, MgF2, and quartz） was conducted with a number of different erodents （glass bead, and angular SiC, SiO2, Al2O3） by a homemade gas-blasting erosion tester. The influence of impact angle, impact velocity, erodent, and erosion time on the erosion rate and the effect of erosion on their IR transmittance were studied. The dam- aged surface morphology was characterized by scanning electron microscopy, and the erosion mechanism was explored. All of the materials show the maximum in wear versus impact angle at 90°, confirming their brittle failure behavior. It is found that the erosion rate is dependent on the erodent velocity by a power law, and it is highly correlated to the hardness of the erodent. The erosion rate-time curves do not show an incubation state, but an accelerated erosion period followed a maximum erosion （steady state）. The decrease of IR transmittance is direct proportion to the erosion rate. Although the material loss occurs primarily by brittle process, ductile behavior is clearly an important feature, especially for MgF2 and ZnS.

Research on Infrared Emissivity and Laser Reflectivity of Sn_(1−x)Er_(x)O_(2)Micro/Nanofibers Based on First-Principles

Sn_(1−x)Er_(x)O_(2)(x=0%,8%,16%,24%)micro/nanofibers were prepared by electrospinning combined with heat treatment using erbium nitrate,stannous chloride and polyvinylpyrrolidone(PVP)as raw materials.The target products were characterized by thermogravimetric analyzer,X-ray diffrotometer,fourier transform infrared spectrometer,scanning electron microscope,spectrophotometer and infrared emissivity tester,and the effects of Er^(3+)doping on its infrared and laser emissivity were studied.At the same time,the Sn_(1−x)Er_(x)O_(2)(x=0%,16%)doping models were constructed based on the first principles of density functional theory,and the related optoelectronic properties such as their energy band structure,density of states,reflectivity and dielectric constant were analyzed,and further explained the mechanism of Er^(3+)doping on SnO_(2)infrared emissivity and laser absorption from the point of electronic structure.The results showed that after calcination at 600℃,single rutile type SnO_(2)was formed,and the crystal structure was not changed by doping Er^(3+).The calcined products showed good fiber morphology,and the average fiber diameter was 402 nm.The infrared emissivity and resistivity of the samples both decreased first and then increased with the increase of Er^(3+)doping amount.When x=16%,the infrared emis-sivity of the sample was at least 0.71;and Er^(3+)doping can effectively reduce the reflectivity of SnO_(2)at 1.06μm and 1.55μm,when x=16%,its reflectivity at 1.06μm and 1.55μm are 50.5%and 40%,respectively,when x=24%,the reflectivity at 1.06μm and 1.55μm wavelengths are 47.3%and 42.1%,respectively.At the same time,the change of carrier concentration and electron transition before and after Er^(3+)doping were described by first-principle calculation,and the regulation mechanism of infrared emissivity and laser reflectivity was explained.This study provides a certain experimental and theoretical basis for the development of a single-type,light-weight and easily prepared infrared and laser compatible-stealth material.

Research status and challenges in the manufacturing of IR conformal optics

The infrared conformal window is one of the most critical components in aircraft.Conformal windows with high performance bring low aberrations,high aerodynamic performance,reliability in extreme working environments,and added value for aircraft.Through the past decades,remarkable advances have been achieved in manufacturing technologies for conformal windows,where the machining accuracy approaches the nanometer level,and the surface form becomes more complex.These advances are critical to aircraft development,and these manufacturing technologies also have significant reference values for other directions of the ultra-precision machining field.In this review,the infrared materials suitable for manufacturing conformal windows are introduced and compared with insights into their performances.The remarkable advances and concrete work accomplished by researchers are reviewed.The challenges in manufacturing conformal windows that should be faced in the future are discussed.

Image Processing Technology of Flaws within Infrared Transmitting Glasses

We investigated image processing algorithms of the original infrared glass flaw image. Using the Laplacian edge enhancement following LSD （Line Segment Detector） algorithm, we can get a good flaw image very consistent with the original one. This study is very helpful to further enhance the infrared glass flaw inspection technique.

Recent progress on sulfide infrared nonlinear optical materials with large SHG response and wide band gap

As the core device of all-solid-state laser,infrared(IR)nonlinear optical(NLO)material plays a critical role in exploring new coherent lights by frequency conversion technologies,which are widely used in noninvasive medical diagnostics,spectroscopy,environmental monitoring and long-distance laser communication.To satisfy the growing demand of current laser technology in IR regions,high performance NLO materials with large second-harmonic generation(SHG)response,high laser-induced damage threshold(LIDT)and wide transparency range are highly expected.Recently,numerous efforts and advances have been achieved in sulfide system.This review highlights the progress of high-performance sulfide IR NLO materials with a good balance between strong SHG response(≥1.0×AgGaS_(2))and wide band gap(≥3.0 eV)since 2018.The chemical synthesis,crystal structure,optical properties and structure-property relationship of 13 high performance metal sulfide IR NLO materials are summarized and reviewed in detail.Finally,the potential opportunities and challenges in IR NLO materials are discussed.

MECHANICAL PROPERTIES OF HOT PRESSED ZINC SULPHIDEDIAMOND COMPOSITES

ZnS-Diatnond cotnPOsites (ZnS/D) were fabricated by hot pressing to obtain a ZnS ithered transparent materials with incmeed toughness. The relations of the mechanical properties and the diomond contents were investigated. It was determined that,when the content of diamond is in the mnge hem 1% to 10%, the toughness of the composite fits the equation KIC = cexp(a+bx). The constants c, a, and b determined experimentally are 10-6, d.47 and 9.70 respectively.

Designing excellent mid-infrared nonlinear optical materials with fluorooxo-functional group of d^0 transition metal oxyfluorides

Exploration of new infrared(IR) nonlinear optical(NLO) materials is still in urgency owing to the indispensable roles in optoelectronic devices, resource exploration, and long-distance laser communication. The formidable challenge is to balance the contradiction between wide band gaps and large second harmonic generation(SHG) effects in IR NLO materials. In the present work, we proposed new kinds of NLO active units, d^0 transition metal fluorooxofunctional groups for designing mid-IR NLO materials. By studying a series of d^0 transition metal oxyfluorides(TMOFs),the influences of fluorooxo-functional groups with different d^0 configuration cations on the band gap and SHG responses were explored. The results reveal that the fluorooxo-functional groups with different d^0 configuration cations can enlarge band gaps in mid-IR NLO materials. The first-principles calculations demonstrate that the nine alkali/alkaline earth metals d^0 TMOFs exhibit wide band gaps(all the band gaps >3.0 e V), large birefringence Δn(> 0.07), and two W/Mo TMOFs also exhibit large SHG responses. Moreover, by comparing with other fluorooxo-functional groups, it is found that introducing fluorine into building units is an effective way to enhance optical performance. These d^0 TMOFs with superior fluorooxo-functional groups represent a new exploration family of the mid-IR region, which sheds light on the design of mid-IR NLO materials possessing large band gap.

Visible-near infrared ultra-broadband polarization-independent metamaterial perfect absorber involving phase-change materials

We numerically demonstrate a novel ultra-broadband polarization-independent metamaterial perfect absorber in the visible and near-infrared region involving the phase-change material Ge_2Sb_2Te_5(GST).The novel perfect absorber scheme consists of an array of high-index strong-absorbance GST square resonators separated from a continuous Au substrate by a low-index lossless dielectric layer(silica)and a high-index GST planar cavity.Three absorption peaks with the maximal absorbance up to 99.94% are achieved,owing to the excitation of plasmon-like dipolar or quadrupole resonances from the high-index GST resonators and cavity resonances generated by the GST planar cavity.The intensities and positions of the absorption peaks show strong dependence on structural parameters.A heat transfer model is used to investigate the temporal variation of temperature within the GST region.The results show that the temperature of amorphous GST can reach up to 433 K of the phase transition temperature from room temperature in just 0.37 ns with a relatively low incident light intensity of 1.11×10~8W∕m^2,due to the enhanced ultra-broadband light absorbance through strong plasmon resonances and cavity resonance in the absorber.The study suggests a feasible means to lower the power requirements for photonic devices based on a thermal phase change via engineering ultra-broadband light absorbers.

Spectral selectivity in infrared thermal detection

A review is made of the physics and technology of spectrally selective thermal detectors,especially those operating at non-cryogenic temperatures.The background radiation noise fluctuations are rederived for arbitrary spectral characteristics.Infrared absorption due to phonons and free carriers is discussed followed by a review of published works on artificial infrared absorption materials such as patterned grids,nanoparticles,plasmonic structures,metamaterials and others.Subsequently,the literature of the spectral characteristics of broadband thermal detectors and spectrally selective thermal detectors is reviewed.Finally,the authors speculate on the directions that future research and development in the area will take regarding architectures,sensitivity and spectral characteristics.

基于磁控溅射法制备的大面积高质量硒化铂薄膜及其在红外探测中的应用

PtSe_(2)因其可调的带隙、高载流子迁移率和较高的光吸收率在红外探测领域受到广泛的研究和关注.然而,传统的制备方法存在生长条件复杂、生长时间长、铂源和硒源的选择性较低、晶体质量不高、成本昂贵以及大规模制造困难等缺点,限制了其实际应用.在此,我们采用了一种便捷、低成本的磁控共溅射法来制备大面积、高质量的PtSe_(2)薄膜.在不同温度下生长的薄膜的表面形貌和微观结构表征结果表明,我们制备的PtSe_(2)薄膜具有良好的结晶性、可控性、均匀性、较窄带隙和优异的红外波段吸收特性,同时我们还研究了最合适的衬底和生长温度.基于PtSe_(2)的光电探测器展示出良好的红外探测能力和较快的响应速度.尤其值得注意的是,相比于传统制备方法,本研究提出的制备方法的制备时间非常短,为PtSe_(2)大规模应用于下一代红外探测,并与现有的硅技术兼容提供了有益的指导.

The compatibly large nonlinear optical effect and high laser-induced damage threshold in a thiophosphate CsInP_(2)S_(7)constructed with[P_(2)S_(7)]^(4-)and[InS_(6)]^(9-)

It is challenging to cooperatively improve the nonlinear optical(NLO)efficiency and the laser-induced damage threshold(LIDT).This work reports a novel IR NLO materials CsInP_(2)S_(7)(CIPS)designed by combination the strategies of alkali metals substitution and microscopic NLO units PS4 introduction based on AgGaS_(2).CIPS was composed of strongly distorted[InS_(6)]^(9-)octahedra and[P_(2)S_(7)]4-dimers constructed by corner-sharing[PS_(4)]^(3-),which increase the NLO efficiency and decrease thermal expansion anisotropy simultaneously.Compared with AgGaS_(2),CIPS exhibited strong phase matchable NLO response ca.1.1×AGS@2.1μm,high LIDT ca.20.8×AgGaS_(2),and IR transparency up to 15.3μm.Structural analysis and theoretical investigation confirmed that large SHG effect and ultrahigh LIDT of CIPS originated from the synergistic contribution of[InS_(6)]^(9-)octahedra and[P_(2)S_(7)]4-dimers.These results indicate that CIPS is a promising NLO candidate in the mid-IR region,and this study provides a new approach for developing potential NLO-LIDT compatible materials.

Numerical simulation of aerodynamic heating and stresses of chemical vapor deposition ZnS for hypersonic vehicles

Hypersonic vehicles subjected to strong aerodynamic forces and serious aerodynamic heating require more stringent design for an infrared window. In this paper, a finite element analysis is used to present the distributions of thermal and stress fields in the infrared window for hypersonic vehicles based on flowfield studies. A theoretical guidance is provided to evaluate the influence of aerodynamic heating and forces on infrared window materials. The aerodynamic heat flux from Mach 3 to Mach 6 flight at an altitude of 15 km in a standard atmosphere is obtained through flowfield analysis. The thermal and stress responses are then investigated under constant heat transfer coefficient boundary conditions for different Mach numbers. The numerical results show that the maximum stress is higher than the material strength at Mach 6, which means a failure of the material may occur. The maximum stress and temperatures are lower than the material strength and melting point under other conditions, so the material is safe.