双掺杂LiNbO3晶体光折变效应图像存储特性

研究了系列双掺杂(Ce：Fe，Mn：Fe，Ce：Mn)以及不同后处理态(生长态、还原态和氧化态)铌酸锂晶体的透过率光谱和光折变全息存储特性．实验结果表明高掺杂铌酸锂样品的透过率光谱范围较窄；氧化态样品具有较大的透过率光谱范围；还原态样品具有较大的光折变二波耦合增益特性．难于同时获得大的波耦合增益和图像存储质量．     

Sensitivity dependence of surface plasmon resonance based sensors on prism refractive index

We theoretically and experimentally demonstrate that refractive index of the prism used to load metal film has significant influence on sensitivity of surface plasmon resonance based sensors. The prism with lower refractive index gives the sensors a higher sensitivity in detecting refractive index variations of a sample. We attribute this effect to the fact that a prism with low refractive index will increase coupling distance between surface plasmons and the medium under investigation. Foundation item: Supported by Wuhan University and National Education Ministry of China Biography: Wang Guo-ping (1964-), male, Professor, research direction: bolographic materials, diffractive optical elements, optical properties of metallic nanopracticles and metal-dielectric nanostructures     

消逝波激励及增益耦合光纤三色激光辐射

将石英光纤浸入低折射率的染料溶液中,泵浦光沿光纤轴向耦合进入光纤并以全反射方式沿光纤轴向传播,泵浦光的消逝波激励染料分子产生增益.由于增益区域与回音壁模式的消逝场区域在空间很好的重叠,因此显著地提高了泵浦效率,增加了沿光纤轴向的增益长度.将一根直径为265μm的石英光纤浸入三段激光染料溶液中,在622～632,504～518和427～434nm的3个波长范围内同时获得回音壁模式的激光辐射.在消逝波激励及增益耦合方式下,实现了同一根光纤中红绿蓝三色的回音壁模式激光辐射,由此形成一种新型的三色回音壁模式光纤激光器.本文同时从实验和理论方面讨论了回音壁模式激光沿光纤轴向的产生长度随泵浦能量变化的关系.     

Parity-time synthetic photonic lattices

The development of new artificial structures and materials is today one of the major research challenges in optics. In most studies so far, the design of such structures has been based on the judicious manipulation of their refractive index properties. Recently, the prospect of simultaneously using gain and loss was suggested as a new way of achieving optical behaviour that is at present unattainable with standard arrangements. What facilitated these quests is the recently developed notion of 'parity-time symmetry' in optical systems, which allows a controlled interplay between gain and loss. Here we report the experimental observation of light transport in large-scale temporal lattices that are parity-time symmetric. In addition, we demonstrate that periodic structures respecting this symmetry can act as unidirectional invisible media when operated near their exceptional points. Our experimental results represent a step in the application of concepts from parity-time symmetry to a new generation of multifunctional optical devices and networks.     

掺Nd~(3+)硼硅酸盐玻璃的非线性光学特性

在调Q 纳秒Nd: YAG强激光脉冲下,使用闭孔Z-扫描技术研究了硼硅酸盐基质玻璃及其掺Nd3+玻璃的三阶光学非线性特性.发现基质玻璃具有正的三阶非线性折射系数和非线性吸收系数,属于自聚焦反饱和吸收型的光学介质;而随着Nd3+的掺入,该硼硅酸盐玻璃的三阶非线性折射和吸收系数较基质玻璃有明显的增大,远高于一个量级.用开孔Z-扫描实验与光限幅实验进一步验证了掺Nd3+玻璃具有较高的三阶非线性吸收系数,表明Nd3+的掺入提高了硼硅酸盐玻璃在532 nm处的激光防护性能.     

非球面近视眼镜片的优化设计

利用人眼睛的光学系统模型,阐述了非球面镜片的数学方程,并根据像差理论,基于PC片(聚碳酸酯)材料设计了一款折射率为1.59的屈光度为-4.00 D的双非球面近视眼镜片.镜片的中心厚度为1.3 mm,在直径为65 mm的边缘处厚度仅为2.3 mm,试验结果表明,该镜片完全能满足成像要求.     

Three-dimensional optical metamaterial with a negative refractive index

Metamaterials are artificially engineered structures that have properties, such as a negative refractive index, not attainable with naturally occurring materials. Negative-index metamaterials (NIMs) were first demonstrated for microwave frequencies, but it has been challenging to design NIMs for optical frequencies and they have so far been limited to optically thin samples because of significant fabrication challenges and strong energy dissipation in metals. Such thin structures are analogous to a monolayer of atoms, making it difficult to assign bulk properties such as the index of refraction. Negative refraction of surface plasmons was recently demonstrated but was confined to a two-dimensional waveguide. Three-dimensional (3D) optical metamaterials have come into focus recently, including the realization of negative refraction by using layered semiconductor metamaterials and a 3D magnetic metamaterial in the infrared frequencies; however, neither of these had a negative index of refraction. Here we report a 3D optical metamaterial having negative refractive index with a very high figure of merit of 3.5 (that is, low loss). This metamaterial is made of cascaded 'fishnet' structures, with a negative index existing over a broad spectral range. Moreover, it can readily be probed from free space, making it functional for optical devices. We construct a prism made of this optical NIM to demonstrate negative refractive index at optical frequencies, resulting unambiguously from the negative phase evolution of the wave propagating inside the metamaterial. Bulk optical metamaterials open up prospects for studies of 3D optical effects and applications associated with NIMs and zero-index materials such as reversed Doppler effect, superlenses, optical tunnelling devices, compact resonators and highly directional sources.     

Complete photonic bandgaps in 12-fold symmetric quasicrystals

Photonic crystals are attracting current interest for a variety of reasons, such as their ability to inhibit the spontaneous emission of light. This and related properties arise from the formation of photonic bandgaps, whereby multiple scattering of photons by lattices of periodically varying refractive indices acts to prevent the propagation of electromagnetic waves having certain wavelengths. One route to forming photonic crystals is to etch two-dimensional periodic lattices of vertical air holes into dielectric slab waveguides. Such structures can show complete photonic bandgaps, but only for large-diameter air holes in materials of high refractive index (such as gallium arsenide, n = 3.69), which unfortunately leads to significantly reduced optical transmission when combined with optical fibres of low refractive index. It has been suggested that quasicrystalline (rather than periodic) lattices can also possess photonic bandgaps. Here we demonstrate this concept experimentally and show that it enables complete photonic bandgaps--non-directional and for any polarization--to be realized with small air holes in silicon nitride (n = 2.02), and even glass (n = 1.45). These properties make photonic quasicrystals promising for application in a range of optical devices.     

GaAs-SiO_2复合薄膜的非线性光学特性

采用单光束Z扫描技术测量了GaAs－SiO2复合薄膜的光吸收和光折射特性，结果表明：在104W／cm2的辐射光强作用下，复合薄膜的光吸收和光折射表现出明显的非线性特征．根据Z扫描测量理论算得三阶非线性折射率系数和非线性光吸收系数分别为10-6cm2／W；和10-1cm／W量级．运用量子点模型对三阶光学非线性响应增强的机制进行了讨论．     

掺铒聚合物光波导放大器的制备与测试

研究掺铒有机聚合物材料Er(DBM)3Phen/PMMA-GMA的光学性质, 并测试了该聚合物的吸收光谱和折射率等参数, 通过光刻结合反应离子刻蚀技术, 利用该材料制备了掺铒聚合物光波导放大器. 采用光纤与波导放大器的直接端面耦合方法测试了光波导放大器的特性, 结果表明, 当输入信号功率为0.2 mW, 抽运功率为150 mW时, 在1.24 cm长的器件上获得了0.9 dB的相对增益.      

等效折射率模型分析二维光子晶体微谐振腔模态

 采用数值计算方法,利用等效折射率模型研究不同折射率材料制造的二维光子晶体微谐振腔的模态。发现可以通过增加薄膜厚度达到良好的光子局域化。讨论了薄膜层材料折射率分别为n=3.42,2.50,1.80,1.60,薄膜层厚度分别对应为0.1529,0.2182,0.3341,0.4003μm,其等效折射率分别对应于2.81,2.23,1.52,1.38时,达到良好光子局域,说明介质材料与空气折射率差值小的光子晶体微谐振腔结构若要有好的光子局限能力,除了需要靠介质材料本身的全反射效应外,还需有足够厚的膜层厚度。从而找到一个能控制光场分布同时维持单模振荡的机制,揭示微谐振腔体薄膜层厚度对模态影响,为实际研制具有高质量微谐振腔提供了一种较好的预估手段。     

双掺杂LiNbO_3晶体光谱和光折变特性

报道了双掺杂Ce :Fe ,Ce :Mn ,Mn :Fe生长态LiNbO3(LN)的光谱及光折变效应二波耦合增益特性 .研究表明 ,双掺杂浓度较高时 ,生长态的LiNbO3晶体的透过率光谱范围较小 ,光折变效应二波耦合增益较低 .几种双掺杂晶体都比单掺Fe晶体的光折变效应二波耦合增益低 ,表现出较强的抗光折变特性     

Raman injection laser

Stimulated Raman scattering is a nonlinear optical process that, in a broad variety of materials, enables the generation of optical gain at a frequency that is shifted from that of the incident radiation by an amount corresponding to the frequency of an internal oscillation of the material. This effect is the basis for a broad class of tunable sources known as Raman lasers. In general, these sources have only small gain (approximately 10(-9) cm W(-1)) and therefore require external pumping with powerful lasers, which limits their applications. Here we report the realization of a semiconductor injection Raman laser designed to circumvent these limitations. The physics underlying our device differs in a fundamental way from existing Raman lasers: it is based on triply resonant stimulated Raman scattering between quantum-confined states within the active region of a quantum cascade laser that serves as an internal optical pump--the device is driven electrically and no external laser pump is required. This leads to an enhancement of orders of magnitude in the Raman gain, high conversion efficiency and low threshold. Our lasers combine the advantages of nonlinear optical devices and of semiconductor injection lasers, and could lead to a new class of compact and wavelength-agile mid-and far-infrared light sources.     

垒层介质折射率对光量子阱透射谱的影响

利用传输矩阵法理论,研究垒层介质折射率对光量子阱透射谱的影响,结果表明：垒层高折射率介质的折射率越大,光量子阱的透射峰带宽越窄;垒、阱层介质的折射率之和的比值越大,光量子阱的透射峰带宽越窄。光量子透射峰带宽对垒层介质折射率的响应规律,不仅可以解决自然介质的折射率上限问题,而且为设计窄带高品质的光学滤波器件提供理论依据,同时对光量子阱的理论研究也具有积极的指导意义。     

基于熔锥光纤耦合器的溶液浓度传感器

利用2×2熔锥型光纤耦合器,提出一种检测溶液浓度的新方法.首先,根据熔融光纤拉伸锥形曲线和超模耦合器理论,分析计算出熔锥型光纤耦合器输出分光可见度与其耦合锥区外部介质折射率的关系曲线;然后,实验上将2×2单模光纤耦合器浸入一种溶液中,当光经过熔锥耦合区后,其耦合分光可见度将随锥区外部的溶液浓度（折射率）而变化.由此,可实现对溶液浓度的检测.理论计算和实验结果有较好的一致性.     

消失场耦合光纤放大器的理论研究

一、引言随着光纤通信技术的发展,对光纤中光信号直接进行放大的研究引起了各国学者的重视。目前有两类光纤放大技术得到较多的研究。一类是利用光纤中的非线性效应进行光放大。另一类是将光纤的一段以受泵浦作用的有源介质构成,使信号光通过时得到放大。若仅包层由有源介质构成,则信号光通过其消失场与有源介质互作用而获得放大,这便是消失场耦合光纤放大器。本文对这类放大器进行理论分析,对由多模和单模光纤构成放     

格兰-汤姆逊棱镜对单模高斯光束的影响

根据光在格兰-汤姆逊棱镜胶合层中的干涉效应,分析了棱镜对单模高斯光束光强分布的影响.结果表明：对于正入射的单模高斯光束,若棱镜结构角、光学胶折射率和胶合层的厚度三者固定其二,透射光束光强分布将随另一参量的变化作周期性振荡,同时,透射光束的形状也会发生改变;但当固定胶合层厚度及棱镜结构角时,透射光束光强分布随光学胶折射率变化的振荡曲线存在一个平坦区,即当胶合层折射率在1.4655—1.5153时,棱镜对单模高斯光束光强的影响小于1%.     

一个新的脊背式硅光波导定向耦合器计算模型

本文提出了一个导波区域的等效折射率模型，并应用介质光波导的强耦合理论和有效折射率方法，给出一个较合理的大尺寸单模脊背式半导体光集成中定向耦合器的理论计算模型。并给出一系列计算结果。     

掺铁铌镁酸铅一钛酸铅单晶的光折变效应

采用助溶剂法生长了掺杂量分别为0．1wt％和0．01wt％的0．67PMNT-0．33PT单晶．利用二波耦合实验研究了掺铁的弛豫铁电单晶0．67Pb（Mg1／3Nb2,3）03-0．33PbTi03（PMN．PT）的光折变性能．本文测试了样品的消光光谱、电光系数、光诱吸收电场和光电导．最大的增益系数达到了21cm-1,是无掺杂的PMN-PT晶体的两倍．光栅形成速率随铁浓度的升高而降低．     

多光学间隔层结构的聚合物太阳能电池

为提高聚合物太阳能电池中有源层的光吸收,提出了一种新型结构的器件———具有多光学间隔层结构的 聚合物太阳能电池,该结构通过调节多光学间隔层折射率的分布方式,调节有源层内光电场的分布,使有源层 对入射光得到充分吸收,进而优化器件性能。采用传输矩阵法对这种多光学间隔层聚合物太阳能电池进行了 光学模拟,探索了多光学间隔层折射率的分布方式对倒置结构聚合物太阳能电池器件有源层光电场的分布和 短路电流密度( Jsc) 的影响。模拟选取的多光学间隔层是通过在ITO( Indium Tin Oxide) 玻璃衬底上依次旋涂未 掺杂ZnO 和掺杂浓度分别为0． 002 5 mol /L,0． 005 mol /L,0． 01 mol /L 的铯掺杂氧化锌( CZO: Cs doped Zinc Oxide) 薄膜制备而成的。模拟结果显示,采用从上到下铯掺杂浓度依次增加的多光学间隔层结构能有效提高 器件有源层对入射光的光吸收和短路电流密度。