共查询到20条相似文献,搜索用时 31 毫秒
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LI Lian-huang GUO Fu-yuan WANG Li-xiang HU Lin-shun 《半导体光子学与技术》2007,47(1):83-88
As for single mode symmetric step refractive index structure dielectric planar optical waveguide, when its output end is restricted, the diffractive field distribution is derived. It can be expressed as the convolution between the Dirac function and the Sinc and Lorenz functions. It is helpful to deepen the recognition of the restricted diffraction. The characteristic of the diffractive field is discussed. The variational curve of the full angle width at half maximum intensity of central bright fringe versus the half width of slit is presented by numerical calculation, and the fitting curve with the exponential function is close to it. 相似文献
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激励态向列微滴散射理论的修正及其参量拟合 总被引:3,自引:2,他引:3
用反常衍射(ADA)理论与实验数据优化拟合方法分析了聚合物分散液晶(PDLC)微滴在633nm激光照射下的散射特性与微滴尺寸、聚合物折射率的关系。在聚合物分散液晶中除了液晶微滴本身的散射以外,还有例如界面散射、杂质散射、材料折射率不均匀等附加散射因子,考虑这些因素以后对反常衍射散射理论进行了修正,提出用参量拟合来测量聚合物分散液晶中聚合物折射率、微滴半径以及液晶体积百分数等参量的方法。测量了微滴的直径在2μm左右聚合物分散液晶的参量。结果表明,对聚合物分散液晶聚合物折射率的误差在5%以内,而对液晶体积分数的测试误差较大,达到10%左右。 相似文献
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An electric-field-induced refractive index variation in a GaInAs/InP five-layered quantum box structure was observed for the first time. The wavelength dependence of the refractive index variation was measured to confirm the quantum box effect. The size of the GaInAs/InP quantum box was estimated to be (22-30 nm)/sup 2/ with the thickness of 7.5 nm. from the spectral property of the field-induced refractive index variation. The maximum value of the refractive index variation in the quantum box was evaluated to be 7% around 1.52 mu m wavelength at an applied electric field of 8*10/sup 4/ V/Cm.<> 相似文献
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为了分析胶合剂折射率对Glan-Thompson棱镜性能的影响,采用理论分析的方法,得出棱镜视场角以及光正入射和斜入射时棱镜的透射比与胶合剂折射率的关系式。在此基础上,针对几种确定长度孔径比的Glan-Thompson棱镜,利用计算机拟合,取得棱镜视场角及透射比随胶合剂折射率变化的关系曲线,并进行了实验验证。结果表明,对于不同长度孔径比的棱镜,最大视场角不同,且对应不同的胶合剂折射率值;胶合剂折射率等于e光的主折射率时,棱镜有最大透射比;由于棱镜的长度孔径比、最大视场角、透射比以及胶合剂折射率之间有相互制约的关系,采用长度孔径比为2.5的棱镜设计和折射率为1.45~1.46的胶合剂是一种较佳的方案。这一结果对优化Glan-Thompson棱镜的视场角和透射比是有帮助的。 相似文献
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基于倾斜光纤光栅及其表面等离子效应的折射率传感比较研究(英文) 总被引:2,自引:1,他引:1
介绍了倾斜光纤光栅作为折射率传感器的测量原理,给出它的倾斜角8°与中心波长1550nm的反射谱与透射谱,分析了具有表面等离子的倾斜光纤光栅传感机理。为验证折射率传感的可能性与优点,进行了蔗糖浓度溶液的裸倾斜光纤光栅与镀金的倾斜光纤光栅的折射率测量分析,证明镀金后的表面等离子效应倾斜光纤光栅折射率传感器其灵敏度大大增加。 相似文献
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比较研究了液晶分子平行和扭曲排列对TiO2 和SiO2 介质膜交替的一维光子晶体透射谱的影响。向列相液晶平行取向时,光子禁带中出现四个透过峰,中心波长约1 840、1 814、1 466、1 423 nm,加热器件,峰位蓝移,相邻的两个透过峰合二为一。向列相液晶扭曲排列时,光子禁带中出现两个独立透射峰,分别位于1 865、1 489 nm,加热样品峰位蓝移。液晶分子平行排列,液晶层折射率各向异性较明显,光子禁带具有两种偏振模式透过峰。液晶分子扭曲排列,液晶层折射率各向异性不明显,光子禁带只有独立透过峰。加热样品,液晶分子排列变化,引起液晶层有效折射率值改变,透过峰位移动。 相似文献
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用液晶分子运动的动力学方程,求出了激光诱导向列相液晶分子重新取向的取向角、折射率改变、阈值场强和上升时间的近似表达式。讨论了它们随液晶材料参数、激光强度和激光在液晶中传播方向的变化,进行了数值计算。给出了激光能诱导向列相液晶分子重新取向的必备条件,得到向列相液晶的各向异性是其分子重新的取向的根本原因。 相似文献
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研究了金属-介质-金属(MDM)型表面等离子体激元(SPP)光波导的电磁特性。理论计算结果表明,对于633nm的TM偏振入射光,当介质膜层厚度小于85nm时,波导中只能激发产生一阶SPP模(基模),其余高阶模全部截止。随着介质膜厚度增加,高阶SPP模逐渐被激发产生。当介质膜层厚度较小时,SPP模的有效折射率的实部随阶数的增加而减小,而虚部则随阶数的增加而增加,SPP基模具有最大传输距离。然而,当MDM波导中的介质层厚度超过0.555μm时,由于三阶SPP模的电磁场主要集中在离金属层相对较远的介质层中,其有效折射率的虚部具有最小值,具有最大的传输距离,而非基模。当入射光波长为633nm介质层厚度为0.9μm时,Ag/SiO2/Ag光波导中三阶SPP模的传输距离达到约150μm。 相似文献
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Kikugawa T. Ravikumar K.G. Shimomura K. Izumi A. Matsubara K. Miyamoto Y. Arai S. Suematsu Y. 《Photonics Technology Letters, IEEE》1989,1(6):126-128
An intersectional optical switch structure with an intersecting angle of 6° was fabricated on an organometallic vapor-phase epitaxy (OMVPE) grown GaInAs/InP multiple quantum-well (MQW) layered wafer. Switching operation using field-induced refractive index variation was successfully demonstrated at the reverse bias voltage of 8 V for the 1.6 μm wavelength region. Based on this switching, the field-induced refractive index variation in the QW was estimated as around 1% 相似文献
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基于光学琼斯矩阵理论,研究掺杂Sm_2O_3的向列相液晶TEB30A在弱磁场中的光栅衍射特性。结果表明,自然光通过处在弱磁场中的适量配比的Sm_2O_3/TEB30A样品后,会在远场产生衍射条纹,且衍射条纹会随外磁场强度的增加而出现动态的变化。产生衍射条纹是由于适量的Sm_2O_3的掺杂,使得向列相液晶TEB30A的折射率各向异性Δn沿外磁场方向呈现周期分布,形成了液晶光栅;当外磁场强度发生变化时,处在外磁场中的Sm_2O_3粒子和液晶分子的分布会随之发生变化,导致Δn沿外磁场分布的周期发生变化,从而引起液晶光栅常数发生变化,因此,衍射条纹呈现出动态变化的效应。模拟结果表明,当外磁场强度由0.464 9T增加到0.518 5T时,液晶光栅常数由0.5cm降到0.4cm。这一技术研究方法将大大降低液晶光栅的成本,同时,弱磁场环境也为使用者提供了一种安全的使用环境。 相似文献
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通过抛磨单模-多模-单模(Single mode-Multimode-Single mode,SMS)光纤结构,设计制作一种光纤折射率传感器。多模光纤选用的是纤芯直径为16μm的锗芯光纤,纤芯直径较小,使制作的传感器尺寸较小,从而在传感应用中具有较高的样品利用率。单模光纤纤芯直径为8.4μm,可确保抛磨至多模光纤纤芯附近时单模光纤的纤芯不被破坏。SMS被AB胶固定在玻璃槽内,使得侧面抛磨光纤具有很好的鲁棒性,可重复使用性。制备并侧面抛磨了锗芯光纤长度分别为0μm、23μm、70μm、690μm、2 mm的SMS光纤结构。对产生的传输光谱进行测量,发现前4个样品随着周围环境折射率的增加,谐振波长向长波长处偏移;而前3个样品的折射率测量灵敏度随着锗芯光纤长度的增加而提高。当锗芯光纤长度为70μm时,在1.333~1.367折射率区间内,灵敏度可以达到623.5 nm/RIU。然而,过长的锗芯光纤导致折射率测量灵敏度降低。当锗芯光纤长度为2 mm时,抛磨过程中激发产生了包层模,导致传输光谱复杂、不稳定,而且长波处产生了较大的插入损耗。 相似文献
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The enhancement mode GaN metal-insulator-semiconductor field effect transistor (E-MISFET) is successfully fabricated on a GaN/A1GaN/GaN double heterojunction structure with SiO2 as the insulator layer. The enhancement mode DC characteristics have been first achieved in the device with the gate-length of 6μm,10μm and gate-width of 100μm. The device with gate-length of 6μm shows the DC transconductance of 0.6 mS/mm and the maximum drain-source current of 0.5mA. The gate leakage current is lower than 10-6A at the bias of -10V while the gate breakdown voltage is higher than 20V. This result proves the presence of a piezoelectric field in the heterojunction,the strongly asymmetric band bending and the carriers distribution caused by the piezoelectric field. 相似文献
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Electrically controlled room temperature terahertz phase shifter with liquid crystal 总被引:1,自引:0,他引:1
Tsong-Ru Tsai Chao-Yuan Chen Ru-Pin Pan Ci-Ling Pan Xi-Cheng Zhang 《Microwave and Wireless Components Letters, IEEE》2004,14(2):77-79
We present the use of electrically controlled birefringence in a nematic liquid crystal cell for phase shifting of electromagnetic waves up to terahertz frequencies. This device was operated at room temperature and a maximum phase shift of 4.07/spl deg/ was demonstrated at 1.07 THz when the interaction length was 38.6 /spl mu/m. The driving voltage and corresponding field were 176.8 V (rms) and 589.3 V/cm, respectively. 相似文献
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Fascinating nematic‐ and smectic‐like self‐assembled arrays are observed for gold nanorods partially capped with either laterally or terminally attached nematic liquid crystals upon slow evaporation of an organic solvent on TEM grids. These arrays can be manipulated and reoriented by applying an external magnetic field from quasi‐planar to vertical similar to a Fréedericksz transition of common organic nematic liquid crystals. Birefringence and thin film textures of these self‐assembled gold nanorod arrays observed by polarized optical microscopy are strongly reminiscent of common organic nematic liquid crystal textures between crossed polarizers and, additionally, support the formation of ordered liquid crystal‐like anisotropic superstructures. The ordering within these arrays is also confirmed in bulk samples using small angle X‐ray scattering (SAXS). 相似文献
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Iam Choon Khoo Min-Yi Shih Wood M.V. Guenther B.D. Pao Hsu Chen Simoni F. Slussarenko S.S. Francescangeli O. Lucchetti L. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1999,87(11):1897-1911
The basic mechanisms of photo-induced space charge field formation, director axis re-orientation, and refractive index changes in fullerene C60- and dye-doped nematic liquid crystals films are presented. In particular, in aligned methyl-red-doped nematic liquid crystal film, we observe a nonlinear index change coefficient as high as 10 cm2/W, associated with purely optically induced liquid crystal director axis re-orientation. Experimental observations of dynamic and high-resolution storage holographic grating formation, two beam coupling with gain of nearly 3000 cm-1, optical limiting action at nanowatt cw laser power, and incoherent-coherent image conversion at μW/cm2 light intensity level are discussed 相似文献
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角锥棱镜的入射角及有效反射面积分析 总被引:1,自引:0,他引:1
基于角锥棱镜的基本结构及定向反射的光学特性,证明了同一光束出射点与入射点的对称关系以及不同入射光束出射点与对应顶点投影点的偏移量关系。推导出不同入射条件下角锥棱镜最大入射角及有效反射面积的理论计算方法,并给出最大入射角随方位角和折射率变化的规律图线及有效反射面积随入射角、方位角、折射率变化的规律图线。研究为角锥棱镜阵列的有效反射面积、回波能量的计算、误差分析等提供理论基础,且对正确设计使用角锥棱镜具有重要的理论指导意义。 相似文献