中波红外短波通滤光片的设计与镀制技术研究

研究了中波红外宽光谱短波通滤光片优化设计和镀制,论述了设计该种滤光片的原则和方法。根据等效折射率理论,以周期性对称膜系为基础,使用部分膜层优化方法,设计了中波红外宽光谱短波通滤光片,在2 300～4 700 nm透射波段范围上的平均透射率设计值大于90%,在5 000～6 300 nm截止波段范围上的平均透射率小于1.00%。采用"会聚光红外光学系统"和等离子体辅助沉积工艺实验制备了滤光片。实验表明,在透射波段范围上的平均透射率约为83%,截止波段的平均透射率约为0.45%。结果表明,部分膜层优化方法设计的膜系,膜层结构简单,有利于膜层厚度的监控。     

用逐层法设计Rh-Si真空紫外高反膜

本文简要阐述了"逐层"设计方法,并将其用于真空紫外波段高反膜的设计。利用Matlab软件编程设计,计算了50 nm~200 nm波段范围内高反膜系及其反射率。并与同样以熔融石英为基底、不同膜材组合所达到的膜系反射率进行了对比,反射率增大明显。同时计算了实验中出现膜厚误差时对反射率造成的影响。     

改进遗传算法在CMP终点检测的应用

提出了一种基于反射法的化学机械抛光(CMP)在线终点判定方法。首先通过改进的单纯形混合遗传算法(GA),对SiO₂薄膜的膜厚与折射率进行了拟合,再以200～1200nm波段内反射率平均值作为特征值,得到了不同膜厚条件下的反射率平均值参照表。以实时反射率与预设膜厚反射率的差方和、特征值大小及其变化趋势这2个条件作为CMP终点判定条件。实验结果表明:混合算法拟合膜厚平均相对误差小于0.21%,折射率平均相对误差小于1.07%;特征值计算速度快,满足在线动态抛光的时间要求。     

孟琴镜双波段内高反射膜

本文叙述了孟琴镜双波段内高反射膜的设计和制备技术。实验发现了获得最高内反射率的最佳铝膜厚度。并给出了实验结果:在0.49～0.69μm波段平均内反射率为96.5～97.5％,在1.06μm内反射率为90％。     

光学显示PC镜片多层反射膜的设计与制备

光学显示仪器前的镜片需要通过镀膜来对特定波段形成高反射,国内绝大多数的光学显示镜片还是玻璃,本文以聚碳酸酯(PC)镜片作为基底,采用真空镀膜技术,在聚碳酸酯(PC)镜片上镀高反射膜,研究了不同膜系结构(层数不同)的反射膜对特定波段的反射效果。研究结果表明,采用了5层膜的设计,PC在可见光区的400nm波段到700nm波段的最高反射率从9.5%上升到85%。PC在特定波段的反射率得到了明显的提高。     

梯度折射率宽带减反射光伏玻璃研究

采用二次腐蚀法制备了梯度折射率减反射光伏玻璃。SEM分析表明,多孔减反射层的微结构尺度在20～30nm左右,膜层厚度为100～300nm。通过计算模拟,确定了膜层折射率分布形式为Gaussian-like型。制备的梯度折射率减反射光伏玻璃透过率>96%的带宽超过了1200nm;在390～1022nm波段的透过率>99%;在350～1084nm的双面反射率<1%,其中624～922nm的双面反射率低于0.2%。     

1064 nm负滤光片的设计与制备北大核心CSCD

针对当前可见-近红外光电探测器的激光防护要求,研究了1064 nm负滤光片的设计和制备。基于等效折射率理论,综合考虑光谱和场强分布优化,设计了由SiO2/Y_(2)O_(3)/H4组合的规整膜系和SiO2/H4组合的非规整膜系负滤光片;采用离子束辅助热蒸发沉积方式对负滤光片进行了制备,并测试了其光学和抗激光损伤性能。结果表明:在膜系结构G|(0.5LH0.5L)s|A两侧匹配减反膜可以有效减小通带波纹,调整膜系最外层厚度可以同时改善膜系的光谱特性和电场强度分布。镀制的规整膜系负滤光片在400~900 nm和1200~2000 nm波段平均透过率分别为89.98%和93.21%,1064 nm透过率为1.29%,激光损伤阈值为6.0 J/cm^(2);非规整膜系负滤光片在650~900 nm和1200~2000 nm波段平均透过率分别为93.70%和94.99%,1064 nm透过率为1.60%,激光损伤阈值为6.8 J/cm^(2)。     

一种长波红外宽光谱长波通滤光片的设计与镀制

长波红外宽光谱长波通滤光片是光谱成像技术中重要的光学元件。本文研究了一种宽光谱长波通滤光片优化设计,论述了设计长波红外宽光谱长波通滤光片的设计原则和方法。根据等效折射率理论,以周期性对称膜系为基础,使用压缩透射区内波纹幅度的部分膜层优化方法,设计了满足性能指标要求的长波红外长波通滤光片。经过优化,所设计的膜系高透射波段内的平均透射率大于90%,高透射区内的最低透射率也高于85%。截止波段内的平均透射率小于1%,截止区内的最高透射率也低于5%。研究表明,部分膜层优化方法设计的膜系,膜层结构简单,有利于膜层厚度的监控,既能克服全自动优化方法给工艺上带来的困难,又弥补了解析法设计膜系时不能调整光谱特性的不足。     

全角度高反射率DBR对GaN基蓝光Mini-LED芯片发光性能的提升

该文采用Essential Macleod软件设计了一种在420 nm～480 nm波段且具有全入射角度、高反射率(大于96%)的TiO2/SiO2分布布拉格反射镜(DBR)膜系,并采用这种全角度高反射率DBR膜系作为GaN基蓝光Mini-LED芯片的反射镜。研究结果表明,与对应唯一中心波长的传统结构DBR膜系相比,它具有全角度高反射率DBR膜系的蓝光Mini-LED芯片的I-V特性、光场分布形态且高温老化特性保持不变,在5 mA的工作电流下,输出的光功率和插座效率分别提升了5.6%和5.4%,其原因是全角度高反射率DBR膜系克服了传统结构DBR膜系在大角度入射时反射率下降的缺点。     

新型双通道日夜滤光片的设计与镀制

红外相机和监控系统在日夜成像时使用日夜滤光片代替红外截止滤光片,以保证白天成像无色差,同时晚上能成黑白像.本文采用Essential Macleod软件设计新型双通道日夜滤光片光谱.光谱中440～640nm的平均透射率大于90％,650～ 1100 nm波段截止,红外截止区域在940nm存在带通,其平均透过率小于20％,带宽小于40nm.采用离子束辅助电子束蒸发的方法,通过优化工艺参数、减小膜层误差,制备得到满足设计要求的K9玻璃基底双通道日夜滤光片.     

Numerical and experimental study of disordered multilayers for broadband x-ray reflection

The effect of layer thickness disorder in periodic multilayers on x-ray reflectivity is investigated numerically and experimentally. We present ensemble calculations, taking into account absorption and interfacial roughness. It is demonstrated that layer thickness disorder yields band broadening and increased integrated reflectivity For applications we concentrate on extrema of the ensembles, giving the highest integrated reflectivity We develop global optimization methods that can also be used to generate specified reflection band structures. In a few examples, applications of the optimization methods are discussed. To illustrate the practical applicability of the methods, we compare experimental realizations to the calculation. In one case we achieve a 42% increase in integrated reflectivity in the 130 ? < λ < 190 ? spectral range with respect to a periodic multilayer with its first-order Bragg peak in the center of that range. Accurate control of layer thicknesses is our main experimental obstacle.     

Optimization of multilayer mirrors at 13.4 nm with more than two materials

The design of multilayer mirrors with more than two materials is one of the key technologies for investigating lithography. We study a new procedure for optimizing multilayer mirrors of different combinations of materials at a wavelength of 13.4 nm. By adding Be and C layers in different orders to a Si/Mo stack, we have observed enhancement of the reflectivity and a reduction in the number of layers. The Luus-Jaakola optimization procedure has been implemented for the global optimization of the multilayer mirrors. With this algorithm it is not necessary to specify initially the number of layers present in a given design.     

Highly dispersive mirror in Ta2O5/SiO2 for femtosecond lasers designed by inverse spectral theory

A highly dispersive mirror for dispersion compensation in femtosecond lasers is designed by inverse spectral theory. The design of a simple quarter-wave Bragg reflector can be modified by moving the poles in the optical impedance found in the photonic stop band. These spectral quantities are used as independent variables in the numerical optimization because they have no effect on the location of the photonic stop band, and so the design requirements to obtain a high reflectivity and a specific delay spectrum are decoupled. The design was fabricated by ion-beam sputtering. A group delay dispersion of -300 fs(2) was measured over a bandwidth of 28 nm, with a remaining reflectivity of greater than 99% in this range. The mirrors were used to make two Ti:sapphire lasers with 10- and 4-mm-long crystals, both of which generated near-transform-limited pulses of 35-fs duration. Because of the high dispersion of the mirrors, the laser cavities needed only five and three bounces from the mirrors, thus keeping reflection losses to a minimum.     

Design, fabrication, and analysis of chirped multilayer mirrors for reflection of extreme-ultraviolet attosecond pulses

Chirped Mo/Si multilayer coatings have been designed, fabricated, and characterized for use in extreme-ultraviolet attosecond experiments. By numerically simulating the reflection of the attosecond pulse from a multilayer mirror during the optimization procedure based on a genetic algorithm, we obtain optimized layer designs. We show that normal incidence chirped multilayer mirrors capable of reflecting pulses of approximately 100 attoseconds (as) duration can be designed by enhancing the reflectivity bandwidth and optimizing the phase-shift behavior. The chirped multilayer coatings have been fabricated by electron-beam evaporation in an ultrahigh vacuum in combination with ion-beam polishing of the interfaces and in situ reflectivity measurement for layer thickness control. To analyze the aperiodic layer structure by hard-x-ray reflectometry, we have developed an automatic fitting procedure that allows us to determine the individual layer thicknesses with an error of less than 0.05 nm. The fabricated chirped mirror may be used for production of 150-160 as pulses.     

Reflection filter with high reflectivity and narrow bandwidth

A kind of reflection filter with a narrow bandwidth and high reflectivity is designed as being composed of an all-dielectric Fabry-Perot filter, a high-reflectivity Ag film, and especially an ultrathin metallic film, n approximately k. Exemplary structures and some formulas concerning spectral-reflection performances, such as general reflectivity, maximum reflectivity, and the halfwidth of the reflection band, are given. Experiments show the validity of this design.     

Characterization of sputtered nickel/carbon multilayers with soft-x-ray reflectivity measurements

Several sputtered Ni/C multilayer mirrors with periods between 3.8 and 6.0 nm were investigated with the HASYLAB reflectometer to determine the peak reflectivity and the internal structure of the multilayers. The enhanced reflectivity in the Bragg maximum, especially below 284 eV (carbon K edge), is interesting for practical applications. For both materials (Ni and C), the optical constants were previously obtained from angular-dependent reflectivity measurements. The layer thicknesses, interface roughnesses, and mean thickness errors of multilayer mirrors are obtained from least-squares fits of theoretical reflectivity curves. A model is presented to describe the influence of interface roughness on other parameters obtained from the analysis. All Ni/C multilayers, with Ar as the sputter gas, were produced in the low-pressure triode-assisted sputtering facility of Sincrotrone Trieste.     

Multilayer amorphous hydrogenated carbon (a-C:H) and SiOx doped a-C:H films for optical applications

In this study SiO_x doped amorphous hydrogenated carbon (a-C:H) films were formed from hexamethyldisiloxane (with hydrogen transport gas) by closed drift ion beam deposition applying variable ion beam energy (300-800 eV). The band gap dependence on the deposition energy was determined and used in production of SiO_x doped a-C:H and a-C:H (formed from acetylene gas) multilayer (two and four layers) stack. Optical properties of the multilayer structures as well as individual layers were analysed in the UV-VIS-NIR range (200-1000 nm). It was shown that employing double or four layer systems, the reflectivity of the multilayer structure-crystalline silicon can be tuned to almost 0% at specific wavelength range (550-950 nm), important in solar cell applications.     

Wide-field-of-view GaAs/AlxOy one-dimensional photonic crystal filter

The design, fabrication, and characterization of a one-dimensional photonic crystal optical filter that has a relatively narrow, flat-topped passband within a wide stop band and small angular sensitivity is presented. The filter is based on a one-dimensional photonic crystal structure that has multiple defects, facilitating simultaneous minimization of the angular sensitivity and optimization of the passband's characteristics. We use epitaxially grown and selectively oxidized GaAs/AlxOy multilayers to achieve a high-index-contrast material system and incorporate the experimentally determined optical and material properties into the design of the device. A flat-topped bandpass filter with a bandwidth of 65 nm and a wide field of view of 50 degrees is experimentally characterized and compared with the design predictions.     

Design of multilayer extreme-ultraviolet mirrors for enhanced reflectivity

We show numerically that the reflectivity of multilayer extreme-UV (EUV) mirrors tuned for the 11-14-nm spectral region, for which the two-component, Mo/Be and Mo/Si multilayer systems with constant layer thickness are commonly used, can be enhanced significantly when we incorporate additional materials within the stack. The reflectivity performance of the quarter-wavelength multilayers can be enhanced further by global optimization procedures with which the layer thicknesses are varied for optimum performance. By incorporating additional materials of differing complex refractive indices-e.g., Rh, Ru, Sr, Pd, and RbCl-in various regions of the stack, we observed peak reflectivity enhancements of as much as ~5% for a single reflector compared with standard unoptimized stacks. We show that, in an EUV optical system with nine near-normal-incidence mirror surfaces, the optical throughput may be increased by a factor as great as 2. We also show that protective capping layers, in addition to protecting the mirrors from environmental attack, may serve to improve the reflectivity characteristics.     

High-efficiency dielectric reflection gratings: design, fabrication, and analysis

We report on reflection gratings produced entirely of dielectric materials. This gives the opportunity to enhance the laser damage threshold over that occurring in conventional metal gratings used for chirped-pulse-amplification, high-power lasers. The design of the system combines a dielectric mirror and a well-defined corrugated top layer to obtain optimum results. The rules that have to be considered for the design optimization are described. We optimized the parameters of a dielectric grating with a binary structure and theoretically obtained 100% reflectivity for the -1 order in the Littrow mounting for a 45 degrees angle of incidence. Subsequently we fabricated gratings by structuring a low-refractive-index top layer of a multilayer stack with electron-beam lithography. The multilayer system was fabricated by conventional sputtering techniques onto a flat fused-silica substrate. The parameters of the device were measured and controlled by light scatterometer equipment. We measured 97% diffraction efficiency in the -1 order and damage thresholds of 4.4 and 0.18 J/cm(2) with 5-ns and 1-ps laser pulses, respectively, at a wavelength of 532 nm in working conditions.