双层矩形位相光栅的分束特性

对由两矩形位相光栅构成的双层体积全息光栅的分束特性进行了优化设计，获得了扇出光束数分别为２，３和５，总衍射效率高于８９％，光强分布不均匀性小于５％的分束器。     

亚波长光栅的偏振闪耀特性

 使用琼斯矩阵的方法推导了连续结构亚波长光栅的衍射方程,给出了光栅衍射效率表达式,对偏振特性与衍射特性进行了研究。发现连续结构亚波长光栅仅存在３个衍射级,总衍射效率为100%,且衍射效率可在衍射级间任意分配,0级的偏振态与入射光的偏振态相同,±1级衍射光偏振态与入射光无关,－1级为左旋圆偏振光,＋1级为右旋圆偏振光。通过设置入射光偏振态与光栅相位延迟等参数,可使光栅具有闪耀特性,据此可用于设计高效偏振光分束器和偏振光开关。     

基于修正简化模式法的熔融石英光栅分束器设计

对用于光栅优化设计初值估计的简化模式法(SMM)进行了修正。考虑介质光栅的反射对透射率的影响,从多层膜等效的角度结合模式理论,推导出介质光栅的透射效率公式,实现了对SMM的修正。计算结果表明,与SMM相比,修正后的方法与严格耦合波(RCWA)的计算偏差大大缩小,TE和TM波都小于2%。因此相对于只能提供设计参数优化初值的SMM,该方法可对光栅参数进行优化;与RCWA相比,该方法将透射光栅的衍射效率表达成模式的相位差偏移和光栅与空气导纳之差引起的反射,更直观地展示了光栅衍射的物理过程。基于此修正的简化模式法(MSMM),优化设计了一个双端口光栅分束器,该光栅在1020~1100nm波段,TE波和TM波的0级和-1级透射效率都在50%左右,具有较好的分束效果。     

基于严格耦合波理论的宽光谱金属介质膜光栅衍射特性分析

基于严格耦合波理论建立了金属介质膜光栅的衍射机理模型,给出了TE模式金属介质膜光栅衍射效率的表达式.以-1级衍射效率和工作带宽为评价函数,对金属介质膜光栅的表面浮雕结构进行了优化设计.对于800 nm和1053 nm为中心的TE波,设计的金属介质膜光栅-1级衍射效率优于97%的工作带宽分别达到130 nm和150 nm,最后讨论了设计的宽光谱高衍射效率金属介质膜光栅的制备工艺容差.此研究对于提高脉宽压缩光栅的性能具有重要的意义. 关键词： 衍射效率 金属介质膜光栅 严格耦合波理论     

基于SOI的亚波长偏振分束器的研究

运用严格耦合波理论对亚波长光栅的模场分布进行讨论,通过位相匹配方程建立衍射级、光栅矢量和波导传输常数的关系,得到波导光栅实现偏振分束功能时对应的设计参数;针对布拉格反射层良好的反射特性,设计了一种亚波长偏振分束器。为了提高光栅的耦合效率,在基底增加Bragg反射层,将传统偏振分束器的透射光反射,与输入光相干叠加,满足相位匹配条件后耦合输出,使耦合效率大大增加。     

自支撑透射光栅的设计、制作和测试

采用标量衍射理论和严格耦合波理论分别计算和讨论了金自支撑透射光栅的衍射效率随波长和光栅周期变化的情况并设计了光栅的结构参数.制作了周期为300 nm、线宽/周期比为055、厚度为200 nm、总面积为1 mm×1 mm、有效面积比为65%的金自支撑透射光栅.在国家同步辐射实验室检测了该光栅在55—38 nm波长范围内的绝对衍射效率.检测结果表明所制作的光栅在8 nm附近具有接近10%的最大衍射效率,并且该光栅对于波长15—35 nm范围内的极紫外波段具有基本稳定的衍射效率.     

自支撑透射光栅的设计、制作和测试

采用标量衍射理论和严格耦合波理论分别计算和讨论了金自支撑透射光栅的衍射效率随波长和光栅周期变化的情况并设计了光栅的结构参数.制作了周期为300 nm、线宽/周期比为055、厚度为200 nm、总面积为1 mm×1 mm、有效面积比为65%的金自支撑透射光栅.在国家同步辐射实验室检测了该光栅在55—38 nm波长范围内的绝对衍射效率.检测结果表明所制作的光栅在8 nm附近具有接近10%的最大衍射效率,并且该光栅对于波长15—35 nm范围内的极紫外波段具有基本稳定的衍射效率. 关键词： 自支撑透射光栅 电子束光刻 电镀     

高效全偏振矩形闪耀光栅的设计(英文)

入射光在光栅内传输时将激发产生离散模.本文采用模态法调节光栅内离散模的传输特性,使TE和TM偏振光所激发的0、1模为传输模,其余高阶模为消逝模.通过调控0模和1模间的累积相位差,对衍射光进行调控,实现了-1级近100%的高效衍射.采用模态法分三部设计了共振域的矩形全偏振闪耀光栅:1)根据光栅的共振条件给出光栅周期,光栅周期越大槽深越小;2)根据特征模方程计算出光栅占空比;3)根据耦合模条件计算机光栅槽深.实验结果表明,该光栅的TE和TM偏振光同时具备近100%的-1级衍射效率.给出了633nm波长-1级矩形石英全偏振闪耀光栅的典型设计实例,计算结果表明:所设计的全偏振闪耀光栅对TE和TM偏振入射光的-1级衍射效率分别高达96.7%和98.1%,且具有较宽的入射角及入射波长的变化适应范围,较大的制作容差.     

光栅衍射效率的二阶标量近似法研究

详细介绍了计算光栅衍射效率的二阶标量近似法,推导出一种简单有效的计算光栅衍射效率的近似公式.给出了利用近似公式对几种情况下光栅衍射效率的计算结果,并与普通标量法、严格矢量法的计算结果进行了比较.     

双层矩形相位光栅的变分束特性

报道了双层矩形相位光栅的变分束特性。发迹入射光照明方向,由同一双层矩形相位光栅获得了光束数分别２、３、４和５,总衍射效率高于７０％的扇出光。     

用于共孔径相干合成的衍射光学元件设计

分析了衍射光学元件实现共孔径相干合成的物理过程,建立了基于衍射光学元件的共孔径相干合成数学模型,推导了合成光束复振幅与入射光束和衍射光学元件相位分布之间的关系。提出用合成光束强度分布的均匀性作为评价函数的优化方法,获得了一维衍射合束器的相位分布。与文献报道的衍射光学元件分束器相比,可获得更高的合成效率。采用模拟退火算法结合随机并行梯度下降算法优化合束器设计,提高了计算效率,获得了多束衍射合束器的相位分布和合成效率。分析了单子束失效及合束器像差对合成效率的影响,结果表明:随着合束数量的增加,单子束失效对合成效率的影响逐渐减小;若使合成效率退化小于5%,衍射光学元件的波像差均方根值应控制在λ/28以内。     

High-throughput, high-damage-threshold broadband beam splitter for high-order harmonics in the extreme-ultraviolet region

We demonstrate a high-throughput and high-damage-threshold beam splitter for high-order harmonics in the soft-x-ray region that uses Si and (or) SiC plates set at Brewster's angle with respect to the pump wavelength. The beam splitters are guaranteed to have a damage threshold of at least 0.8 TW/cm2 (average power density, 0.25 W/cm2) and an attenuation rate of 10(-4)-10(-5) for a 30-fs pump pulse. The measured reflection efficiency at the 27th harmonic (29.6 nm) was 0.56 for Si and 0.45 for SiC. These beam splitters are useful not only for high harmonics but also for longitudinally pumped x-ray lasers.     

非对称偏振分束光栅的矢量衍射优化设计

基于严格耦合波理论分析了一种非对称偏振分束光栅的设计。这种偏振分束光栅分别在1级和0级衍射级次上衍射TE和TM偏振波。介绍了利用遗传算法设计偏振分束光栅的方法,并给出了优化实例。仿真结果表明:在设计波长为1.55时,TE偏振波在1级的衍射效率大于93%,TM偏振波在0级的衍射效率大于99%,此时1级和0级的透射消光比分别达到了9914.1和46841.5。通过对设计结果的分析发现,该偏振分束光栅在设计波长附近100nm的波长范围内都具有较高的消光比(大于100),达到了较好的偏振分束效果。     

Diffraction grating with rectangular grooves exceeding 80% diffraction efficiency

A novel design for a surface relief grating with rectangular grooves is presented. The first reflected diffraction order shows experimentally 84% diffraction efficiency for a metallic grating. The required binary surface relief can be manufactured by using one single microlithographic fabrication step similar to standard processes in microelectronics. Each period of the grating consists of a subwavelength “minilattice” with a variable duty cycle. A theoretical model of the structure is presented and compared to measurements at 10.6 μm wavelength. Applications ranging from deflectors, polarizing beam splitters, variable attenuators to general diffractive components such as kinoforms for laser beam shaping are proposed.     

DESIGN OF 2-D QUASI-OPTICAL BEAM SPLITTERS USING ANALYTICAL GRADIENTS

Quasi-optical systems comprised of diffractive phase elements (DPEs) are designed as beam splitters. The design tasks are reformulated as optimization problems in which target functionals are defined. Analytical gradients are derived to those functionals, which can be passed to gradient methods to efficiently determine the DPEs. Rayleigh-Sommerfeld diffraction integrals are applied to compute the wave propagation in free-space between parallel planes in the quasi-optical systems. Numerical results for several beam splitters are depicted. Furthermore a procedure is proposed, how the phase functions of the DPEs could be smoothed out.     

铝对过渡金属离子掺杂的二氧化硅溶胶凝胶玻璃发光性质的影响

用溶胶凝胶法制备了过渡金属离子(Ni2+,Mn2+和Cu2+)单掺、铝共掺的二氧化硅玻璃,测量了荧光光谱、吸收光谱和红外光谱,研究了Al3+对过镀金属离子在二氧化硅玻璃中发光性质的影响。研究结果表明,Al3+对过渡金属离子的发光性质有着显著影响:Ni2+,Mn2+和Cu+的发光强度大幅度提高,Mn2+的发光峰峰位改变。     

Binary diffractive beam splitters with arbitrary diffraction angles

Diffractive optical beam splitters designed with iterative Fourier transform type algorithms can produce only certain diffraction angles given by the spatial frequencies used for the computations, which are multiples of a certain base spatial frequency. We have developed a design algorithm that overcomes this limitation and can be used to compute binary diffractive elements with arbitrary diffraction angles. The simulated and experimentally measured properties of optical elements producing beam arrays in circular arrangements are presented and discussed.     

局域中空光束中原子的强度梯度冷却

提出了一种采用蓝失谐局域中空光束实现中性原子冷却与囚禁的新方法，并采用Monte-Carlo模拟方法研究了局域中空光束中原子强度梯度冷却（即Sisyphus冷却）的 动力学过程. 研究发现一个温度约为5μK和密度为10^12—10^13cm^3的超冷原子样品可以在我们的单束局域中空光束势阱中获得，而且这一原子密度可通过改变聚焦系统的相对孔径来加以调控. 因此，这一蓝失谐的局域中空光束还可用于实现全光型玻色-爱因斯坦凝聚. 关键词： 局域中空光束 原子囚禁 强度梯度冷却     

Design of near-field irregular diffractive optical elements by use of a multiresolution direct binary search method

A multiresolution direct binary search iterative procedure is used to design small dielectric irregular diffractive optical elements that have subwavelength features and achieve near-field focusing below the diffraction limit. Designs with a single focus or with two foci, depending on wavelength or polarization, illustrate the possible functionalities available from the large number of degrees of freedom. These examples suggest that the concept of such elements may find applications in near-field lithography, wavelength-division multiplexing, spectral analysis, and polarization beam splitters.     

Design of photonic crystal power beam splitters via corrugated and gratinglike surfaces

In this work, we use the finite-difference time-domain method in conjunction with a genetic algorithm to design photonic crystal power beam splitters based upon a typical planar photonic crystal waveguide with corrugated surfaces or gratinglike surfaces covered behind the termination. Considering a power detector placed at different locations in the output field, we have obtained several beam splitters designs with different splitting angles. These beam splitters have high splitting efficiency and power intensity in the propagation direction.