基于偏振分束器的C波段可调谐薄膜滤波器

针对多腔窄带薄膜滤光片在倾斜入射时会产生严重的偏振相关损耗问题,研制了一种基于双折射晶体偏振分束器、信道间隔为100 GHz的角度可调薄膜滤波器.该方法可简化倾斜入射时多腔窄带薄膜滤光片消偏振膜系结构,通过对入射光信号偏振态的控制,仅使用常规窄带滤光片就能实现角度调谐其中心透射波长.该可调谐滤波器件具有结构简单、成本低...     

一种低偏振可调谐光滤波器的优化设计

光通信系统要求可调谐光滤波器(TOF)隔离度高,偏振敏感性低,目前基于角度调谐滤光片技术的TOF很难满足这一要求.通过膜系仿真分析了此类TOF透射谱劣化的原因.针对不同偏振态的光束在倾斜入射时中心波长及带宽分离现象,提出一种对称反转光路对TOF透射谱进行优化,可在整个透射范围内(C波段)将TOF的隔离度提高到30dB以...     

多层介质高反射膜的散射特性研究

为了研究多层介质高反射薄膜的散射特性减小光学薄膜的散射损耗,以多层光学薄膜矢量光散射理论为基础,利用光学薄膜的总散射损耗与光学薄膜双向反射分布函数的关系,研究了多层介质高反射薄膜分别在膜层界面粗糙度为完全相关和完全非相关模型下入射角和偏振状态对总散射损耗的影响,以及入射波长对总散射损耗的影响.理论研究结果表明,随着入射角的变化p偏振入射光引起的p偏振的总散射损耗强烈依赖于膜层界面粗糙度的相关特性,尤其是在布儒斯特角附近更为明显;此外,通过对介质高反射膜在两种不同模型下的总散射损耗随入射波长的变化与其反射率谱的比较发现,完全相关模型下的总散射损耗与反射率谱的变化趋势一致,完全非相关模型则恰好反之.     

遗传算法在窄带滤光片膜系设计中的应用

研究了遗传算法在窄带滤光片膜系设计中的应用。介绍了遗传算法的运算原理、适应度函数和运行参数的涵义;建立了窄带滤光片的评价函数和适应度函数,并给出其遗传算法的程序设计方法;以带宽4nm、中心波长1.55μm的窄带滤光片为例进行了遗传算法的实际膜系设计。结果表明遗传算法适用窄带滤光片的膜系设计。     

一种窄带导模共振负滤光片的设计

由于弱调制光栅可以等效为平面波导,本文从平面波导的本征方程出发,导出垂直入射时弱调制光栅共振位置的表达式.分别以单层、双层膜系导模共振光栅结构为例,研究了光栅层厚度、周期、占空比对共振波长的影响.结合光学薄膜理论设计出一种窄带导模共振负滤光片.由于导模共振对入射波参数和光栅参数都极为敏感,具有窄带效应,用来制作窄带负滤波片非常可行.     

波长可调谐深紫外窄带光源模块的设计及验证

本文提出了一种中心波长连续可调的光源模块,实现了深紫外光源的窄带输出.设计的光源模块由氘灯、角度旋转台、滤光片旋转轮、不同中心波长的滤光片(220 nm,230 nm,240 nm,250 nm,260 nm,270 nm,280 nm)和光学透镜组成.基于多光束干涉理论,通过分析出射光的中心波长和入射角度之间的关系,...     

基于半导体纳米材料的偏振光发射:从材料到发光二极管（英文）

由于偏光片、彩色滤光片和液晶层等结构的损耗,基于背光源技术的液晶显示器的整体效率不足5%.自发射发光二极管(LED)不但具有巨大的市场潜力,而且能够满足未来显示的需求,迎来了巨大的发展机遇.更重要的是,由于避免了偏光片造成的光损失,偏振LED可以提高背景光利用效率.因此,亟需寻找有效的方法组装高质量的各向异性纳米材料薄膜,从而制备出具有高偏振度和高外量子效率的偏振LED.本文介绍了一些半导体纳米材料的光电特性及其在偏振LED中的潜在应用.综述了在偏振光发射领域从材料到薄膜,再到LED的研究进展;总结和比较了构建偏振光发射薄膜和LED的不同组装策略;最后,讨论了当前面临的挑战,并对偏振LED的潜在商业应用价值进行了展望.我们希望这篇综述能够对偏振LED当前研究进展进行有价值的总结,并对其未来发展激发一些新的、切实可行的想法.     

基于穆勒系数测量的目标识别技术研究

目标对入射偏振光的退偏振特性与目标的材料有着密切的联系,并且对激光入射角的变化特别敏感,而目标的穆勒矩阵完全描述了其对入射偏振光的退偏振特性。因此可以利用测量目标的穆勒系数实现识别目标的目的。利用这一思想提出一种基于穆勒系数测量的目标识别技术。实验采用He-Ne激光作为照明光源,获取不同入射角时铝制飞机模型机翼和涂漆木板的穆勒系数。结果显示:两者的穆勒系数具有明显差异,随着激光入射角增加,两者的穆勒系数先减小后增大。对实验结果进行详细分析,并给出处于杂乱背景中飞机模型的强度图像和偏振图像。     

窄带介质滤光片的填充密度效应

实验观察到,窄带介质滤光片的填充密度效应,不但表现于滤光片峰值波长向长波漂移,而且显著地表现于峰值透射率的增加。依据填充密度理论模型,提出了膜层吸水后减少散射光损失的观点,从而解释了峰值波长透射率的增加。并依据填充密度理论,计算了峰值波长漂移的数值,计算的结果与实验测得的结果基本相符。最后,作为窄带介质滤光片填充密度效应的应用之一,研究了窄带介质滤光片胶合中峰值波长移动的规律,给出了防止峰值波长移动的简便可行的方法。     

银纳米颗粒有序阵列光学偏振玻璃特性研究

银纳米椭球微粒有序掺杂的光学偏振玻璃具有光学玻璃的高透过率特性和本征的偏振特性,是综合性能好的光学偏振器件。利用米氏理论和电偶极子理论分析了光入射到椭球形银纳米微粒产生的消光特性和偏振机理;建立椭球形纳米微粒周期阵列分布的光学偏振玻璃模型,采用有限元数值算法模拟计算近红外光入射该模型后的偏振光输出特性。通过优化玻璃内部椭球微粒的几何参数,获得波长在700~1 100nm近红外全波段内的偏振玻璃的透过率达到80%以上,消光比达20dB以上;尤其当波长在740~840nm范围内,透过率高达90%以上,消光比达50dB以上。     

Wavelength-division multiplexed thin-film filters used in tilted incident angles of light

The properties of wavelength-division multiplexed (WDM) narrowband filters used in tilted collimated light are described. The wavelength shift for s polarization in a low-index-spacer filter is larger than that for p polarization when the filter is tilted, but it is smaller in a high-index-spacer filter. Therefore the passbands of the tilted filter can be centered at the same wavelength for two polarization modes by use of high- and low-index materials, as appropriate, as spacers or by selection of a moderate-index material instead of a spacer. With such spacers, WDM filters used for incident angles of 20 degrees or even greater are constructed. Experimental results agree with the computed ones.     

Design of 50 G nonpolarizing dense wavelength division multiplexer angle-tuning bandpass filter

Transmission characteristic differences of a narrow bandpass filter between p- and s-polarized light, especially the central wavelength separation, will corrupt the performance of the filter when the incidence is oblique. In this paper, by adding high-index materials asymmetrically to both sides of a low-index spacer, which tunes the equivalent index of the spacer, the central wavelengths of the two polarizations coincide perfectly when in 20° incidence; with different reflected layers on the two sides of the spacers and replacing some reflected layers with equivalent layers, the 0.5 dB normalized passband width is kept at 0.2 nm, which meets the requirement of the 50 G dense wavelength division multiplexer filter.     

Nonpolarizing guided-mode resonant grating filter for oblique incidence

A new type of guided-mode resonant grating filter is described. The filter is independent of polarization state for oblique incidence. The filter has a crossed grating structure, and the plane of incidence on the filter contains the symmetric axis of the grating structure. Theoretical considerations and numerical calculations using two-dimensional rigorous coupled-wave analysis show that a rhombic lattice structure is suitable to such filters. In this configuration an incident light wave is diffracted into the waveguide and is divided into two propagation modes whose directions are symmetric with respect to the plane of incidence. In particular, when the propagation directions of the two modes are perpendicular to each other, the fill factor of grating structure can be approximately 50%. The filter was designed for an incident angle of 45 degrees. Tolerances of setting errors and fabrication errors for this filter were estimated by numerical calculations.     

Two-chamber integrated multichannel narrowband filter prepared by a multistep etching method

A new, to the best of our knowledge, method, which combines the multistep ion-etching method with a traditional narrowband filter coating technique, is developed to prepare a two-chamber integrated multichannel filter. The influence of film deposition and etch technique on the shape and height of the narrow transmittance peaks is analyzed. A 32-channel narrowband integrated filter is fabricated with a homemade ion-etching machine and a coating machine. Every channel is distinctly separated and the FWHM is 1% of its central wavelength. The feasibility of the technique will be useful in the fabrication of a higher integrated multichannel narrowband filter.     

Tuning of emission wavelength in chiral photonic crystals with an anisotropic defect layer

We considered some properties of defect modes in chiral photonic crystals with an anisotropic defect layer at oblique light incidence. The problem was solved by Ambartsumian's layer addition method. We investigated some peculiarities of the discussed system's reflection spectra and also the polarization plane rotation spectra and polarization ellipticity spectra of the oblique light incidence for both the minimum and essential influence of the dielectric borders. Our investigations show that there is a possibility of rather a wide change of the emission wavelength in the subject system by changing the incidence angle, or by changing the doped dye concentration, or by changing the pumping wave intensity. We also investigated absorption (emission) peculiarities at different dye molecule concentration and at different chiral photonic crystal thicknesses.     

TM Wave Resonant Peaks in Defect-Free Multilayer Structures Containing Nano-Scale Y123 Superconductors

In the ultraviolet region and by using transfer matrix method, the transmission spectra of electromagnetic waves through one-dimensional quasiperiodic photonic structures consisting of high-temperature yttrium barium copper oxide (Y123) superconductor and strontium titanate (STO) dielectric layers are studied theoretically. It is shown that for TE polarization at oblique incidence two band gaps are created, while for TM polarization three band gaps are produced. The edges of both polarizations shift to higher wavelengths by increasing incident angles. Also, for angles of incidence greater than 78^°, the second gap for TM-polarized light is eliminated. It is also found that in the supposed structure the number of PBGs can be modulated by the thickness of dielectric layer, while it is nearly insensitive to the thickness of superconductor layer. Interestingly, for the incidence angles other than normal incidence the structure can exhibit some narrow resonant peaks near wavelengths where the electric permittivity of the superconductor layer changes sign. These resonant peaks are only for TM polarization and not present for TE polarization. This structure can act as a very compact polarization sensitive splitters and defect-free multichannel narrowband tunable filters.     

Diffraction of horizontally polarized ultrasonic plane waves on a periodically corrugated solid-liquid interface for normal incidence and Brewster angle incidence

The theory, and the use at normal incidence, of shear-vertically polarized waves (with polarization vector in the plane containing the incident wave vector and the normal on the interface) using the mode conversion method has been tackled by others. Here we develop the theory for shear-horizontally polarized incident waves (with polarization vector perpendicular to both the normal on the interface and the incoming wave vector). We take into account normal incidence as well as oblique incidence. For normal incidence, we discover the generation of Love waves. If oblique incidence is considered, we discover the existence of a Brewster angle of incidence, comparable with the Brewster angle in optics, in which a diffraction grating can be used as a polarization filter.     

Design and characteristics of polarization-insensitive resonant gratings for color filtering

A method of designing polarization-insensitive color filters with guided-mode resonance grating is presented. The influence of incident conditions on exciting waveguide mode is investigated, and we find that polarization insensitivity may occur at the full conical incidence. Using rigorous coupled-wave analysis, we mainly analyze the effects of waveguide thickness and fill factor on the diffracted efficiency of the grating filter. The final structural parameters of the devices for three primary colors are collected after optimization, and the calculated results show that the spectral reflectance of each color filter is basically identical for different polarization states of incident light. Moreover, field analysis by the finite-difference time-domain technique indicates that two symmetric modes are excited between the waveguide layer and substrate under full conical incidence, which is coincident with the previous theoretical study. The reported work will eliminate the restriction of polarization-dependence of color filters and greatly expand their application range.     

Beam displacement and distortion effects in narrowband optical thin-film filters

A three-dimensional model for beam propagation through optical interference filters is presented. The model predicts a wavelength-dependent lateral beam displacement of tens or hundreds of micrometers in narrowband filters at an angle of incidence of only 3 degrees to 5 degrees . The effects of filter bandwidth, wavelength offset, angle of incidence, and beam size are investigated. The effect is experimentally confirmed for a 100 GHz filter at a 3.5 degrees angle of incidence.