Chemically Responsive Elastomers Exhibiting Unity‐Order Refractive Index Modulation

Chameleons are masters of light, expertly changing their color, pattern, and reflectivity in response to their environment. Engineered materials that share this tunability can be transformative, enabling active camouflage, tunable holograms, and novel colorimetric medical sensors. While progress has been made in creating artificial chameleon skin, existing schemes often require external power, are not continuously tunable, and may prove too stiff or bulky for applications. Here, a chemically tunable, large‐area metamaterial is demonstrated that accesses a wide range of colors and refractive indices. An ordered monolayer of nanoresonators is fabricated, then its optical response is dynamically tuned by infiltrating its polymer substrate with solvents. The material shows a strong magnetic response with a dependence on resonator spacing that leads to a highly tunable effective permittivity, permeability, and refractive index spanning negative and positive values. The unity‐order index tuning exceeds that of traditional electro‐optic and photochromic materials and is robust to cycling, providing a path toward programmable optical elements and responsive light routing.     

Synthesis,structural, linear and nonlinear optical properties of chromium doped SnO2 thin films

The present work concentrates on some physical investigation of the undoped and Cr doped SnO₂ thin films deposited onto precleaned glass substrates by the spray pyrolysis system. The physical properties of the undoped and Cr doped SnO₂ thin films were investigated by the X-ray diffraction (XRD), atomic force electron microscope (AFM), field emission scanning electron microscope (FESEM), four-probe method and double beam spectrophotometer. The undoped and Cr doped SnO₂ films display a polycrystalline nature with orthorhombic crystal structure. The linear optical constants energy gap E_g, refractive index n, absorption coefficient α, static refractive index n_o, oscillation energy E_o, dispersion energy E_d and the Urbach energy of the undoped and Cr doped SnO₂ thin films were evaluated. The investigated films exhibit a direct energy gap and their values decrease with the increasing of Cr doping content while the Urbach energy follows a reverse behavior. On the other hand, the nonlinear optical constants (third-order nonlinear susceptibility ${\mathit{\chi }}^{(3)}$ and nonlinear refractive index n₂) have been increased with increasing the Cr doping content. Finally, it has been found that the sheet resistance and conductivity of the synthesized thin films were enhanced by increasing the Cr doping content. The 5?wt% Cr doped SnO₂ thin film has a high value of the figure of merit among other films.     

Effects of alkali metal ion on imprinting GRIN microstructure in GeS2-Ga2S3-MCl (M=Na,K, Cs) glasses for visible to mid-infrared microgratings

Gradient refractive index (GRIN) micro-optics present unique opportunities for control of the chromatic properties, new degrees of freedom for optical design as well as the potential for use in new optical system applications. GRIN microgratings were imprinted in GeS₂-Ga₂S₃-MCl (M = Na, K, Cs) chalcohalide glasses by microthermal poling, and the effects of the type and concentration of alkali cations on their performance were investigated. Two effective imprinting formation regions of the GRIN microstructure based on the poling saturation voltage (U_s) and glass composition are observed at fixed poling time and temperature. The U_s increases from 140 to 750 and 2600 V in accordance with the activation energy (E_a) of alkali ions (Na⁺ to K⁺ and Cs⁺) increasing from 45.15 to 58.62 and 92.58 kJ/mol for studied samples. The saturated numbers of diffraction order (N_s) of the gratings in these samples are 7, 9 and 6, respectively, the highest number being provided by the K⁺-containing sample. This is in accordance with imprinting-induced phase differences (0.14λ, 0.19λ and 0.09λ) measured in the fabricated samples containing Na⁺, K⁺ and Cs⁺ ions. Furthermore, the U_s of samples decreases from 1500 to 300 V with four concentrations of K⁺ from 10 to 30%, associated with their E_a of K⁺ decreasing from 69.62 to 53.46 kJ/mol, while N_s increases from 8 to 14, which is attributed to the increase of the phase difference in the GRIN structures. The controllable GRIN microstructures are realized by adjusting the type and concentration of alkali cations in chalcohalide glasses, which is expected to drive the design of broadband GRIN microgratings.     

Thermo-optical characterization of CdZnS nanoparticle colloids

Thermo-optical properties of cadmium zinc sulfide (CdZnS) nanoparticle colloids are investigated by interferometry technique. The nanoparticle colloids are synthesized by an improved co-precipitation method. Transmission electron microscopy, UV–vis spectrometry and X-ray diffraction analysis are used to characterize the CdZnS nanocrystals. The thermo-optic coefficient of the colloids has been determined using a Fizeau interferometer. For this purpose, the interference patterns are deformed by a photothermal phase shift which is locally induced in the sample by the focused pump laser beam. The change in the refractive index at this region imposes a shift on the phase of the fringe patterns. Fourier analysis performed on the interference patterns allows us to estimate the values of the thermo-optic coefficient and nonlinear refractive index of the sample. It is shown that the CdZnS nanoparticle colloids enhance the absorption of the laser light and induce high rise in the temperature of the sample, which leads to the nonlinear phase shift.     

Thermal history and its implications: A case study for ion exchange

Glasses containing monovalent species can be chemically strengthened by the replacement of smaller ions in the glass with larger external ions in the near glass surface. This type of ion exchange puts glass surface under high compressive stress (CS). Glass mainly fails from tension with the presence of surface flaws. Chemical strengthening can change the stress at the flaw tip from tension to compression and further stop the flaw from propagating. Glass damage resistance is therefore significantly improved. For the same glass composition, glass thermal histories can affect the magnitude and depth of the CS generated during ion exchange. In this study, the impact of thermal history on glass physical properties and ion exchange attributes in one alkali-containing glass formed by fusion draw process was investigated. Multiple thermal treatments were done to rewrite the glass thermal histories. Glass density, refractive index, and ion-exchange properties as a function of the thermal treatment were studied. It is concluded that ion exchange-related properties change dramatically with the glass thermal history.     

Reducing treatment zone diameter in orthokeratology and its effect on peripheral ocular refraction

PurposeTo determine whether orthokeratology (OK) induced treatment zone (TZ) diameter can be reduced by altering OK lens design, and if so the impact of modifying TZ diameter on relative peripheral refraction (RPR).Methods16 subjects (mean age 23.4 ± 1.5 years; 8 female) completed the study. Standard (Control) OK lens design (PJ, Capricornia, Australia) or a modified version (Test) where the back optic zone diameter was reduced, and back optic zone asphericity and intermediate lens curves were altered, were worn overnight only for 7-nights in a randomised double masked order, with a minimum 1-week wash out (no lens wear) between lens designs. Full correction of refractive error was targeted. Refraction; best corrected visual acuity (BCVA); RPR (Shin-Nippon NVision-k 5001) along the horizontal and vertical meridians; and corneal topography (Medmont E300) were measured before starting lens wear and in the morning after lens removal after the seventh night of lens wear for both lens designs. TZ diameter and decentration was calculated from corneal topography.ResultsAfter 7-nights of wear both lens designs created -2.00D refraction effect with no significant difference in refractive effect or change to BCVA between the designs. The Test design created a significantly smaller horizontal (4.78 ± 0.37 vs 5.70 ± 0.37 mm, p < 0.001) and vertical (5.09 ± 0.51 vs 5.92 ± 0.51 mm p < 0.001) TZ diameter. The TZ was decentered inferior temporal with no significant difference between designs. There was no significant difference between the lens designs in RPR along the horizontal and vertical meridians at any measurement period.ConclusionsOK induced TZ diameter can be reliably reduced by altering OK lens design without detrimentally effecting lens centration or refractive effect. Reducing TZ diameter did not alter RPR, though measurement artifacts could be responsible for masking an effect. Longitudinal studies are needed to assess whether smaller TZ OK lens designs increase efficacy for slowing progression of myopia.     

空间红外大口径折射式低温镜头设计与验证

针对目标探测类空间红外相机大范围成像、高灵敏度探测、高精度定位等应用需求,文中提出采用像方远心光路和低温光学技术结合的解决方案,设计了物方视场角8°×8°、入瞳口径265 mm、工作温度200 K的像方远心折射式光学系统。镜头最大口径280 mm,采用多级分散的弹性支撑设计,解决大口径低温透镜装框、透镜组件支撑和镜头整体安装各环节的热应力卸载问题。在保证高刚度和低漏热的情况下,使低温下透镜的热应力对镜头能量集中度的影响降低到可接受范围内。镜头完成装调及室温下像质确认后,进行了力学振动试验,并将其制冷到200 K水平测试像质,测试结果表明,镜头能量集中度达到轴上75%,边缘视场72%。     

纳米硅薄膜光学性质的测定与研究

通过测定纳米硅薄膜的透射谱,建立计算模型计算得出薄膜样品的折射率、厚度、吸收系数和光能隙.计算结果表明这种半导体材料在620 nm波长附近的折射率约为3.4,计算得到的厚度与用台阶仪测量的结果吻合很好.在620 nm波长附近的吸收系数介于吸收系数较小的晶体硅与吸收系数较大的非晶硅之间,光能隙约为1.6 eV,两者都随晶态含量增大而呈减小趋势.     

角度位置自动识别的红外折射率测量

为准确快速获得块体硫系玻璃红外波段的折射率,搭建了基于类准直测量法的折射率测量系统。该系统采用液氮制冷的碲镉汞探测器和特殊的光路实现了光强信息的高分辨采集,使用高分辨数据采集卡将角度信息数字化,利用精密步进电机传动控制系统实现了光强信号与位置信号的同步记录。开发的测量软件可自动判别光强峰位信息,自动计算获得待测样品的折射率。对比测试Ge_(20)Sb_(15)Se_(65)、Ge_(28)Sb_(12)Se_(60)、As_2S_3和As_2Se_3商用硫系玻璃在3.39μm和4.8μm处的折射率。实验结果表明,该装置系统测量折射率的标准偏差为10~(-3),测量不确定度为0.002 9,可快速、准确测量块体材料红外波段的折射率。     

食用油品质的光学低相干外差干涉检测法

液体的折射率是一个重要的物理参数,在外界一定的条件下,掌握液体折射率及其变化,则可以了解其纯度、浓度等参数及品质。提出一种用低相干光外差干涉方法测量反复使用食用油的折射率,进而鉴别油的品质。实验以改进的迈克尔逊干涉仪为基础,将样品油放入测量臂光路中,当两束分别来自测量臂与参考臂的低相干光的光程接近相等时,会出现光外差干涉现象。利用光电探测器得到此干涉信号,根据前后相应的光程变化量,进而得到待测样品的折射率。食用油经反复加热1、2、3、5、7次后,葵花油的折射率分别为1.469 5、1.469 7、1.470 1、1.470 7、1.471 3,玉米油的折射率分别为1.468 8、1.469 1、1.469 4、1.470 1、1.471 1。结果表明,该方法可以准确测量出不同加热次数食用油的不同折射率,测量稳定性较高,能快捷、有效地鉴别反复使用的食用油品质。