等离子体浸没离子注入制备黑硅抗反射层及其光学特性研究

表面织构是一种有效降低表面反射率、提高硅基太阳能电池效率的方法. 采用等离子体浸没离子注入的方法制备了黑硅抗反射层.分别通过原子力显微镜和紫外-可见-近红外分光光度计对黑硅样品表面形貌和反射率进行分析, 结果发现黑硅样品表面布满了高度为0—550 nm的山峰状结构, 结构层中硅体积分数和折射率随抗反射层厚度增加而连续降低. 在300—1000 nm波段范围内,黑硅样品的加权平均反射率低至6.0%. 通过传递矩阵方法对黑硅样品反射谱进行模拟,得到的反射谱与实测反射谱非常符合.     

红外低发射率隐身涂层对太赫兹波的反射光谱研究

为研究红外低发射率隐身涂层对太赫兹波的反射特性,制备了红外低发射率隐身涂料,测试了其可见光效果、红外热像图及红外发射率等特性参数。以土黄色红外低发射率涂料为测试样品,利用透射式太赫兹时域光谱系统获得了样品在太赫兹波段的复折射率。分析了特征矩阵理论,并利用特征矩阵理论计算了涂层厚度(0.3~0.5 mm）与入射角度(0°~60°)的变化对入射太赫兹波反射特性的影响。结果表明,在相应厚度及入射角度范围内,太赫兹波在0.8 THz频率下具有多个反射峰值,最高值可达90%以上,有利于实现太赫兹波对红外低发射率隐身涂层下金属目标的探测。此外,涂层厚度变化对入射太赫兹波反射率具有较大影响,涂层越厚,太赫兹波的反射振荡越多,反射峰值越大。入射角度对太赫兹波的反射特性具有一定的影响,但整体影响不大,有利于太赫兹波实现多角度目标的探测。最后,以表面均匀涂覆0.42 mm厚涂料的金属板为测试样品,实验测量了样品在0.1~1.5 THz频率范围内的反射特性,并与部分理论计算结果进行对比。结果表明：实验测量结果与理论计算结果在数值和趋势上较为吻合,但也存在一定的偏差。究其原因,主要由样品厚度和样品参数误差导致,但依然可利用特征矩阵理论研究红外低发射率涂层对太赫兹波的反射光谱特性。     

Evaporation of uniform antireflection coatings on hemispherical lenses to enhance infrared antenna gain

Infrared dipole-coupled bolometers receive radiation more efficiently when illuminated through a high permittivity, antireflection (AR) coated, hemispherical immersion lens. To maintain the enhanced responsivity for all illumination angles, the AR coating must be uniform over the hemispherical surface. An evaporation method for depositing a uniform AR coating on the hemispherical surface is presented. The lens is tilted relative to the source, which can be either electron-beam or thermal, and rotated throughout the deposition. Evaporation at an angle of 70° yields a uniform film with less than 10% thickness variation over a 120° full angle of the hemispherical surface. A theoretical model is developed and compared to profilometer measurements. In all cases, there is general agreement between theory and measurement. A single dipole is fabricated onto the flat surface of an AR-coated germanium immersion lens and the responsivity is measured for both substrate-side and air-side illumination. With a zinc sulfide (ZnS) single-layer AR coating, substrate-side illumination yields a broadside antenna response 49 ± 2.7 times greater than air-side illumination.     

基于频率选择表面的双层改进型互补结构太赫兹带通滤波器研究

通过仿真计算和实验研究了一种基于频率选择表面的双层改进型互补结构太赫兹带通滤波器.对四裂缝互补型电感电容式谐振单元结构进行了改进,可以在提高滤波性能的同时增加单晶石英介质衬底的厚度.利用电磁仿真技术设计并加工了中心频率为0.28 THz的带通滤波器,并利用太赫兹时域光谱仪测试了在0.1—0.6 THz范围内此滤波器的传输频谱特性,实验结果与仿真结果基本一致.结果表明,利用双层改进型互补结构可以设计出对于入射角度不敏感、带外抑制佳、边带陡峭度大、能有效抑制寄生谐振的宽带太赫兹带通滤波器,并降低了加工难度.     

Nanostructured porous SiO2 films for antireflection coatings

Thin films with a low refractive index play an important role in optics, optoelectronics, and microelectronics. In this study, we present nanostructured porous SiO₂ films fabricated by using a glancing angle deposition technique. These nanostructured porous SiO₂ films deposited at an angle of 85° show very low refractive indices of 1.08 at 633 nm. As an application, a four-layer antireflection coating for visible wavelength is designed and fabricated using SiO₂ material only. The normal incidence reflectance of the antireflection coating averaged between 400 and 800 nm is about 0.04%. The microstructure and the surface morphology are also investigated by using a scanning electron microscope.     

太赫兹波发射晶体的亚波长微棱锥增透结构的设计与实验研究

光学整流方法产生太赫兹(THz)辐射常用的非线性发射晶体在THz波段都具有较高的折射率, 使得很大一部分THz波由于晶体表面的菲涅尔反射而无法有效耦合输出. 本文报道了GaP晶体THz波发射器输出表面上亚波长微棱锥增透结构的设计和实验研究. 利用有效介质模型在理论上验证了亚波长光栅结构的增透效果, 并进一步设计了适用于不同频段的增透结构的参数. 实验中, 通过微机械加工手段在GaP晶体输出端面刻划了多种亚波长微棱锥结构, 验证了其增透效果及参数对增透频带的关系. 理论与实验的符合证明该设计思想也可用于其他THz波发射晶体. 关键词： THz波 光学整流 亚波长微棱锥增透结构 微加工     

Maximum time-resolved hemispherical reflectance of absorbing and isotropically scattering media

This paper presents a parametric study of the time-resolved hemispherical reflectance of a plane-parallel slab of homogeneous, cold, absorbing, and isotropically scattering medium exposed to a collimated Gaussian pulse. The front surface of the slab is transparent while the back surface is assumed to be cold and black. The 1-D time-dependent radiation transfer equation is solved using the modified method of characteristics. The parameters explored include (1) the optical thickness, (2) the single scattering albedo of the medium, and (3) the incident pulse width. The study pays particular attention to the maximum transient hemispherical reflectance and identifies optically thin and thick regimes. It shows that the maximum reflectance is independent of the optical thickness in the optically thick regime. In the optically thin regime, however, the maximum hemispherical reflectance depends on all three parameters explored. The transition between the optically thick and thin regimes occurs when the optical thickness is approximately equal to the dimensionless pulse width. Finally, correlations relating the maximum of the hemispherical reflectance as a function of the optical thickness, the single scattering albedo of the materials, and the incident pulse width have been developed. These correlations could be used to retrieve radiation characteristics or serve as initial guesses for more complex inversion schemes accounting for anisotropic scattering.     

Numerical investigation of measurement error of the integrating sphere based on the Monte-Carlo method

To accurately measure the directional-hemispherical reflectance of a material surface using an integrating sphere, we investigated the effects of the integrating sphere’s interior structure and coating properties on the measured data by numerical simulation. The results showed that the integrating sphere’s structure and the reflectance of the coating codetermine the accuracy of the measured results. When the integrating sphere’s structure is fixed, choosing an appropriate internal coating using the method proposed in this paper ensures the accuracy of the results. If a proper coating is not available, we propose a method to effectively correct the measured results.     

利用等效层的消偏振宽带减反膜设计

分析了倾斜入射条件下导致光学薄膜产生偏振的原因,针对不同偏振态的等效导纳与等效相位进行了分析,并计算了对称膜层在45°入射条件下不同偏振态的等效折射率与等效相位厚度,采用等效层方法设计了光学性能良好的600～900 nm波段消偏振宽带减反膜。最后利用电子束蒸发技术制备了薄膜样品,样品的光谱性能完全能够满足使用要求。其中在600～900 nm波段范围内,平均反射率均小于1．38%,反射率的偏振度均低于0．89%。另外,通过对其理论及实验光学性能、角度敏感性、膜层厚度误差敏感性等方面的分析结果可知,对称膜层组合法是设计消除倾斜入射下宽带减反膜偏振效应的一种行之有效的方法。     

基于金属孔阵列的聚酰亚胺薄膜太赫兹探测

优化设计了多种不同孔径和形状的太赫兹波段的亚波长金属孔阵列结构,结合超薄低折射率的聚酰亚胺（PI）薄膜,探索了太赫兹时域光谱技术对超薄低折射率的探测灵敏性。利用飞秒微加工技术制备了一系列亚波长金属孔阵列结构,利用太赫兹时域光谱技术测试了阵列结构的反射波谱,获得了强烈的反射共振现象。然后在亚波长金属孔阵列结构背面叠加PI薄膜,结果表明太赫兹反射峰出现了显著低频移动现象。利用这一现象,实现了低至10 m的PI薄膜的有效探测,说明亚波长金属孔阵列结构在太赫兹传感领域对检测超薄低折射率薄膜材料有极强敏感性。收稿日期:; 修订日期:     

基于金属孔阵列的聚酰亚胺薄膜太赫兹探测

优化设计了多种不同孔径和形状的太赫兹波段的亚波长金属孔阵列结构,结合超薄低折射率的聚酰亚胺（PI）薄膜,探索了太赫兹时域光谱技术对超薄低折射率的探测灵敏性。利用飞秒微加工技术制备了一系列亚波长金属孔阵列结构,利用太赫兹时域光谱技术测试了阵列结构的反射波谱,获得了强烈的反射共振现象。然后在亚波长金属孔阵列结构背面叠加PI薄膜,结果表明太赫兹反射峰出现了显著低频移动现象。利用这一现象,实现了低至10 m的PI薄膜的有效探测,说明亚波长金属孔阵列结构在太赫兹传感领域对检测超薄低折射率薄膜材料有极强敏感性。收稿日期:; 修订日期:     

Bi-directional reflectance study on particulate layers: Effects of pore liquid absorption coefficient

We have made bi-directional reflectance distribution function (BRDF) measurements on particulate layers wetted by absorbing liquids. The measurement results indicate that the BRDF tends to become more Lambertian as the interstitial pore liquid becomes more absorbing. The directional hemispherical reflectance, or albedo, of such a layer decreases nonlinearly with a wetting liquid's absorption coefficient. This behavior may be fit by two empirical relationships which independently treat the reflectance from the front surface and reflectance from the bulk material.     

50~110 nm波段高反射率多层膜的设计与制备

阐述了50~110 nm强吸收波段亚四分之一波长多层膜的设计方法.这种膜系是由强吸收材料叠加而成，每层膜光学厚度小于四分之一个波长.与常规周期多层膜相比，这种膜系更适用于提高强吸收波段的反射率.利用该方法设计了50 nm处高反射多层膜，并以此为初始条件通过Levenberg-Marquart优化方法完成了50~110 nm强吸收波段宽带高反射率Si/W/Co多层膜的设计，其平均反射率达到45%.采用直流磁控溅射方法制备了Si/W/Co多层膜,用X射线衍射仪(XRD)对膜层结构进行了测试，测试结果表明制作出的多层膜结构与设计结构基本相符.     

Design,optimization and fabrication of 2D photonic crystals for solar cells

This paper presents the optimization of 2D photonic crystals (PCs) onto Si wafers to improve the performance of c-Si PV cells. The objective is to find a structure capable of minimizing the reflectance of the Si wafer in the spectral range between 400 nm and 1000 nm. The study has been limited to PCs that can be fabricated and characterized with the tools and technology available and to dimensions in the same order as the visible light wavelength. PCs with different shapes and dimensions have been simulated and finally the optimum structure has been fabricated by a process based on laser interference lithography (LIL) and reactive ion etching (RIE). This optimized PC presents an average reflectance of 3.6% in the selected wavelength range, without any other material used as antireflective coating. This result means a drastic reduction in comparison with reflectance obtained out of the standard wet etch texturization used in current solar cell manufacturing lines.     

Observation of a new type of THz resonance of surface plasmons propagating on metal-film hole arrays

Highly conducting metal-film subwavelength hole arrays, lithographically fabricated on high-resistivity silicon wafers in optical contact with thick silicon plates, have been characterized by terahertz time-domain spectroscopy with subpicosecond resolution and over a frequency range from 0.5 to 3 THz with 5 GHz resolution. A well-defined ringing structure extending to more than 250 psec is observed on the trailing edge of the transmitted THz pulse. In the frequency domain this ringing structure corresponds to a new type of extremely sharp resonant line structure between the fundamental surface plasmon modes of the hole array. A simple theoretical model is presented and shows good agreement with the experimental data.     

离子束溅射制备低应力深紫外光学薄膜

采用离子束溅射制备了Al F3、Gd F3单层膜及193 nm减反和高反膜系,分别使用分光光度计、原子力显微镜和应力仪研究了薄膜的光学特性、微观结构以及残余应力。在优选的沉积参数下制备出消光系数分别为1.1×10~(-4)和3.0×10~(-4)的低损耗AlF_3和GdF_3薄膜,对应的折射率分别为1.43和1.67,193 nm减反膜系的透过率为99.6%,剩余反射几乎为零,而高反膜系的反射率为99.2%,透过率为0.1%。应力测量结果表明,AlF_3薄膜表现为张应力而GdF_3薄膜具有压应力,与沉积条件相关的低生长应力是AlF_3和GdF_3薄膜残余应力较小的主要原因,采用这两种材料制备的减反及高反膜系应力均低于50 MPa。针对平面和曲率半径为240 mm的凸面元件,通过设计修正挡板,250 mm口径膜厚均匀性均优于97%。为亚纳米精度的平面元件镀制193 nm减反膜系,镀膜后RMS由0.177 nm变为0.219 nm。     

THz波在金属镀层空芯波导中传输的理论和实验研究

本文基于微扰法求得不同金属镀层空心圆波导中各模式的损耗系数,对金属镀层空芯波导中THz波传输损耗随金属材料、波导结构等参数的变化关系进行了数值模拟.根据数值分析结果,优化设计并拉制了内径为1.1 mm的镀银空芯波导,实验测得当THz波的频率为2.5 THz时,传输损耗为8.6 dB/m,实现了THz波短距离的有效传输. 关键词： 太赫兹波 金属空芯波导 传输损耗     

A simple fabrication method for mechanically robust superhydrophobic surface by hierarchical aluminum hydroxide structures

Superhydrophobic surfaces with uniformly superhydrophobic surface where nano-scale structures were fabricated by alkali surface modification method and self-assembled monolayer coating. To enhance mechanical durability of the superhydrophobicity, we propose the fabrication process for dual-scale hierarchical structures combining both microstructure via sandblasting techniques and the nanostructured aluminum hydroxide layer. The superhydrophobic surfaces fabricated by both methods exhibited a high water contact angle and very low contact angle hysteresis. By forming the hierarchical structure, the mechanical durability of superhydrophobic aluminum hydroxide surface was improved. The resulting hierarchical structures are suitable for diverse applications of aluminum in various industrial areas, including self-cleaning, anti-frosting, and microfluidic devices for rigorous environments.     

紫外-真空紫外漫反射板的研究

选用在紫外－真空紫外波段反射率较高的铝作基底材料,通过光学研磨加工和光学镀膜处理制成漫反射板;建立了紫外－真空紫外波段漫反射特性测试研究装置,利用该系统进行漫 反射板余弦特性、双向反射比分布函数的测试。结果表明,该漫反射板反射比ρ（ｏ／ｄ）在３１５ｎｍ处为４９％;在正入射情况下,双向反射比分布函数在１５℃￣４０℃范围内偏差优于１１％。     

Measurements and analysis of antireflection coatings reflectivity related to external cavity lasers

Facets of semiconductor optical amplifiers (SOA) designed for external cavity lasers must be coated with an antireflection (AR) film of high quality and extremely low reflectance. Therefore measurements of facet reflectance play a crucial role in the fabrication of such AR coating. The reflectance can be estimated by studying the optical power reflected from the Fabry-Perot cavity formed for that purpose by the examined SOA facet and the end of a single-mode fibre. We have made analysis of practical suitability of such measurement method. Theoretical calculations show that, for the low reflectance coatings, losses due to light coupling into optical fibre cannot be omitted in the analysis of the experimental results. To verify this conclusion a theoretical model was tested for a low reflectance surface and we have found that the relative error of the measurements supported by the theoretical model is on the order of 8%.