亚波长偏振分束光栅的优化设计

采用模态法和严格耦合波法优化设计了矩形石英偏振分束光栅,分析了偏振分束特性.研究表明,当光栅周期约为0.61μm时,TM偏振光两低阶模的折射率差近似为零,而TE偏振光的两低阶传输模则存在一个较大的折射率差,此时石英光栅具有最佳的偏振分束效果,可以将TE偏振和TM偏振入射光分别衍射到-1级与0级透射光束中.对于1.053 μm和1.064 μm波长的入射光,经优化设计光栅的-1级与0级可分别获得超过99%和90%透射衍射效率,透射消光比分别高于28 dB和23 dB.     

近红外 MEMS 闪耀光栅的设计与制作

利用硅的各向异性湿法腐蚀性质,在偏晶向(111)硅基底材料上,设计并制作了闪耀角为8°、周期为4μm的近红外闪耀光栅.设计时考虑了光栅顶部平台对光栅衍射效率的影响,修正了光栅的闪耀角.制作时利用一次性氧化削尖的方法,减少光栅顶部平台的宽度,以提高光栅的衍射效率.利用扫描电子显微镜(SEM)进行光栅形貌测试,结果表明:制作的光栅具有平滑的光学表面和良好的光栅槽形.对光栅进行衍射效率测量,当入射波长为1 392nm时,衍射效率能达到70%以上,表明光栅具有很高的衍射效率,能满足微型近红外光谱仪的使用要求.     

Er-Yb掺杂磷酸盐玻璃平面波导长周期光栅分析

提出了一种基于Er-Yb掺杂磷酸盐玻璃的长周期波导光栅,利用耦合模理论研究了长周期波导光栅的传输特性,分析了长周期光栅的相位匹配特性,讨论了光栅常数和光栅长度对长周期波导光栅传输特性的影响。研究结果表明,2个谐振波长对应于相同的辐射模,当光栅长度一定时,长周期波导光栅的带宽随光栅常数的增加而增大;而当光栅常数一定时,长周期波导光栅的带宽随光栅长度的减小而增加,滤波深度随光栅长度的减小而减小。     

利用最小偏向角法测定光的波长

衍射光栅是一个由大量等间距狭缝组成的集合体 ,如图⑴ ,当一束平行光垂直射入光栅时 ,光波在各个狭缝上发生衍射 ,其衍射主极大位置满足光栅方程 :图 1ｄｓｉｎθｋ =ｋλ(ｋ =0 ,± 1 ,± 2…… ) ( 1 )其中θｋ为第ｋ次衍射明纹所对应的衍射角 ,( 1 )式即平行光垂直入射时的光栅方程。一般情形下 ,设斜入射为α ,如图 ( 2 ) ,相邻两缝上对应两点发出的衍射光程差 ,为δ =ｄ(ｓｉｎθｋ-ｓｉｎα) ,因此出现主极大条件为 :δ =ｄ(ｓｉｎθｋ-ｓｉｎα) =ｋλ(ｋ =0 ,± 1 ,± 2…… ) ( 2 )或δ =ｄ(ｓｉｎθｋ ｓｉｎα) =ｋλ(ｋ =0 ,±…     

完整抛磨光纤光栅3层介质波导模型数值模拟

应用3层结构光纤波导模型,借助计算软件改变外界折射率、剩余包层厚度等参数,对完整抛磨光纤光栅在外界环境影响下的Bragg波长变化进行数值模拟。数值模拟的结果表明,随着外部环境折射率的提高,有效折射率从初值渐骤升至最大值,后略有下降,Bragg波长表现为外界折射率接近纤芯折射率时,红移而又略回蓝移。在设定不同的外界折射率情况下,光纤光栅的有效折射率都呈现出当包层半径较大时保持不变,包层半径减小到某值后光纤光栅的有效折射率突然增加,达到顶峰的有效折射率仍小于各自的外界折射率。所得结果对于侧边抛磨光纤光栅的设计、液位测量和折射率传感技术具有重要的指导意义。     

光纤光栅车辆称重测速关键装置设计与试验

为了满足高速公路计重收费,治理超载超限,以及海关、煤矿、电厂、水泥厂、粮库等货车运货量大且按重量交易的场所的需求,采用光纤布拉格光栅压力传感器与复合材料相结合,构成秤体并实现了车辆的动态称重测速。进一步进行了静态载荷下的仿真试验和动态运行试验,当载荷增加时,不同载荷下测量到的差值比较稳定,静态应变试验最大相对误差为2.7%,动态载荷试验最大相对误差4.7%。试验表明,论文中称重测速装置对载荷的变化敏感,误差小,具有较高的可靠性。     

D-型光纤传感器检测流体折射率的仿真

为了利用D-型光纤传感器来检测流体的折射率或浓度，采用固定波长的入射光，改变入射角度的方法，通过Matlab对模型进行数值模拟研究了光反射强度与纤芯、入射角、金属膜厚度、SiO2膜厚度以及被测介质折射率之间的关系。模拟结果表明，纤芯折射率变大时，共振角减小；当入射角在共振角附近时，光强反射率变化明显；金属膜厚度对光强反射率影响明显，但对共振角影响甚小；不同折射率的被测介质对应的共振角度不同。因此可通过检测不同入射角下的光强反射率，找到共振角，从而达到确定被测流体的折射率或浓度的目的。     

CD光盘轨道间距测量

从合适的角度看光盘,在日光下可见彩色的辐射光带,而且不同的观察角度,光带的色彩不同。当白光照射到这种反射光栅上时,由于光栅衍射的作用,产生彩色光带,其色彩取决于光栅常量和观察角度。本实验就用一种简单的方法来测量CD光盘的光栅常量。     

雨滴击溅与薄层水流混合侵蚀的输沙机理

【目的】针对雨滴击溅与薄层水流混合侵蚀过程输沙机理研究中存在的问题,研究雨滴击溅对坡面径流输沙的影响。【方法】采用室内人工模拟降雨试验,以土娄土、黄绵土和黑垆土为供试土壤,在不同雨滴直径(直径2.22,2.68和3.04mm)、不同坡度(0°,2°和4°)和薄层水流厚度(0,2,4和6mm)条件下,分析单雨滴击溅时,泥沙溅蚀量与水层厚度的关系;多雨滴击溅时,泥沙溅蚀量与薄层水流厚度的关系,分别对二者关系进行拟合;同时,对于多雨滴击溅时,不同薄层水流厚度下黄绵土泥沙溅蚀量和雨滴动能的关系进行了分析。【结果】单雨滴击溅时,泥沙溅蚀量随水层厚度的增加而减少,且雨滴直径越大其扰动水层厚度越大,当雨滴直径由2.22mm增加到3.04mm时,平均扰动水层厚度由10mm增加到14.67mm。多雨滴击溅时,在相同的坡度(0°~4°),不同土壤和雨滴直径下,随薄层水流厚度的增加,泥沙溅蚀量呈先升后降趋势;当薄层水流厚度相同时,随雨滴直径的增加,泥沙溅蚀量呈增大趋势。当雨滴动能不变时,泥沙溅蚀量随着薄层水流厚度的增加而增大;当薄层水流厚度一定时,泥沙溅蚀量随雨滴动能的增加而增大。【结论】建立了单雨滴击溅和多雨滴击溅条件下扰动水层厚度关与泥沙溅蚀量的关系式。     

非匀幅光束在浮雕光栅中的传输特性

利用角谱表示和逆规则傅里叶模式理论,研究了非匀幅光束的典型代表TE线偏振高斯光束在亚波长三角形面型浮雕光栅体内的传输.数值分析表明浮雕层内不同透射深度处的光强分布随着透射深度的变化而变化.最后讨论了入射角、周期等光学参数对出射光强分布的影响.这些结论对高衍射效率亚波长光栅的制作和高功率激光光学元件设计等都具有现实意义.     

光对美洲蛙肌肉纤维衍射强度的分布研究

肌原纤维是由粗丝和细丝重迭而成的Ａ带和只含细丝的Ⅰ带组成，形成了天然光栅，因此可用光学方法探讨肌原纤维分子结构及其动力学问题。试验表明，单色光通过美洲蛙肌原纤维后，衍射光左右两端为非对称性，且左右条纹锋值间隔随肌原纤维节长度增大而减小。肌肉运动有张有弛，于是肌原纤维长度有变异，共变异与非对称有关。当肌原纤维长度增加时，左右两端强度差异变大，而相对应条纹的锋值间隔距离变小。这一现象与布拉格方程和折射     

Picosecond holographic-grating spectroscopy

Interfering light waves produce an optical interference pattern in any medium that interacts with light. This modulation of some physical parameter of the system acts as a classical holographic grating for optical radiation. When such a grating is produced through interaction of pulsed light waves with an optical transition, a transient grating is formed whose decay is a measure of the relaxation time of the excited state. Transient gratings can be formed in real space or in frequency space depending on the time ordering of the interfering light waves. The two gratings are related by a space-time transformation and contain complementary information on the optical dynamics of a system. The status of a grating can be probed by a delayed third pulse, which diffracts off this grating in a direction determined by the wave vector difference of the interfering light beams. This generalized concept of a transient grating can be used to interpret many picosecond-pulse optical experiments on condensed-phase systems. Examples of some low-temperature experiments will be presented. In principle, many of these experiments could also be performed by using stochastic broad-band excitation. In these nonlinear photon-interference experiments the time resolution is determined by the correlation time of the light source rather than its pulse width.     

MATLAB在光学教学中的应用

探讨在基础物理光学教学中,应用MATLAB软件模拟光的双缝干涉、单缝衍射和光栅衍射,以获得良好的课堂教学效果。     

一种实用的微机化光栅测量仪

本文在光栅测量仪的基础上,应用微机技术,充分发挥软件功能,使其智能化,从而使之性能稳定,工作可靠,操作简易,为广泛应用于机械加工,现场检测开辟了新的前景。     

Complex Optical Surfaces Formed by Replica Molding Against Elastomeric Masters

Complex, optically functional surfaces in organic polymers can be fabricated by replicating relief structures present on the surface of an elastomeric master with an ultraviolet or thermally curable organic polymer, while the master is deformed by compression, bending, or stretching. The versatility of this procedure for fabricating surfaces with complex, micrometer- and submicrometer-scale patterns was demonstrated by the production of (i) diffraction gratings with periods smaller than the original grating; (ii) chirped, blazed diffraction gratings (where the period of a chirped grating changes continuously with position) on planar and curved surfaces; (iii) patterned microfeatures on the surfaces of approximately hemispherical objects (for example, an optical surface similar to a fly's eye); and (iv) arrays of rhombic microlenses. These topologically complex, micropatterned surfaces are difficult to fabricate with other techniques.     

Generation of light from free electrons

Experiments with the interaction of a rectangular cross- section beam of electrons which is brought into contact with a metallic diffraction grat e ng produce light variable in wavelength throughout the visible spectrum. Con tinuous variation of the beam thickness shows that light is produced by electrons hundreds of wavelengths from the grating, if the side of the beam near the grating is in contact with it. The results can be accounted for by periodic accelerations of the electrons passing over the surface of the grating. These accelerations are caused by electrostatic forces which in turn are due to the average spacecharge of sheets of elec trons reflected from the grating surface, so that in their space- charge structure the periodicity of the grating rulings is preserved.     

日光光谱的计算机重现与仿真

将日光的可见光谱均匀分割为2000份色光,并计算了各色光的RGB值。以2000份色光为光源,基于Matlab软件重现了标准日光光谱,仿真了日光光栅光谱及日光棱镜光谱。结果表明,重现与仿真的日光光谱,色彩连续、细腻而逼真,可应用于与日光光谱相关的研究与应用领域。     

Luminescent color image generation on porous silicon

Black and white images were projected onto n-type silicon (100) wafers during a photoelectrochemical etch to produce a color image that photoluminesces. The photoluminescence originates from a thin layer of luminescent porous silicon that is produced in the photoetch, and the colors that appear in the etched image arise from thin-film optical interference. A diffraction grating was also photoetched into the substrate, demonstrating simultaneous encoding of a gray-scale image into thin-film interference, luminescence, and diffraction phenomena.