Very-large-mode-area photonic bandgap Bragg fiber polarizing in a wide spectral range

A design of a polarizing all-glass Bragg fiber with a microstructure core has been proposed for the first time. This design provides suppression of high-order modes and of one of the polarization states of the fundamental mode. The polarizing fiber was fabricated by a new, simple method based on a combination of the modified chemical vapor deposition (MCVD) process and the rod-in-tube technique. The mode field area has been found to be about 870 μm2 near λ=1064 nm. The polarization extinction ratio better than 13 dB has been observed over a 33% wavelength range (from 1 to 1.4 μm) after propagation in a 1.7 m fiber piece bent to a radius of 70 cm.     

Hybrid plasmonic waveguide with gain medium for lossless propagation with nanoscale confinement

In this Letter, we propose a hybrid plasmonic nanosystem consisting of a silver cladding layer with a semicylinder bump on top of InGaAsP nanowire. Because of the coupling between the dielectric waveguide mode and surface plasmon polariton mode, the hybrid plasmonic mode can exhibit low loss with strong field localization. The finite element method numerical simulations are employed to evaluate the performances of the hybrid mode. In order to achieve the lossless propagation of the hybrid mode with the mode area of 0.0058(λ2/4) at 1.55 μm, the material gain of 200 nm × 300 nm InGaAsP nanowire should reach 1223 cm?1.     

高磁电阻磁性隧道结的几种微制备方法研究

利用金属掩模法优化了制备磁性隧道结的实验和工艺条件，金属掩模的狭缝宽度为100 μm. 采用4 nm厚的Co₇₅Fe₂₅为铁磁电极和10或08 nm厚的铝氧化物 为势垒膜， 直接制备出了室温隧穿磁电阻（TMR）为30%—48％的磁性隧道结，其结构为Ta(5 nm)/Cu(25 nm)/Ni₇₉Fe₂₁(5 nm)/Ir₂₂Mn₇₈(10 nm)/ Co₇₅Fe₂₅ (4 nm)/Al(08 nm)-O/Co₇₅Fe₂₅(4 nm)/Ni₇₉Fe ₂₁(20 nm)/Ta(5 nm).同时，利用刻槽打孔法和去胶掀离法两种光刻技术并结合Ar离子束刻蚀及化学反应刻 蚀，制备出面积在4 μm×8 μm—20 μm×40 μm、具有室温高TMR和低电阻的高质量磁性 隧道结.300 ℃ 退火前后其室温TMR可分别达到22% 和50%.研究结果表明，采用光刻中的刻 槽打孔或去胶掀离工艺方法制备的小尺寸磁性隧道结，可用于研制磁动态随机存储器和磁读 出头及其他传感器件的磁敏单元. 关键词： 磁性隧道结 隧穿磁电阻 金属掩模法 光刻法     

Semi-elliptical dielectric-loaded surface plasmon-polariton waveguides

Semi-elliptical dielectric-loaded surface plasmon-polariton waveguide (DLSPPW) is proposed. The mode effective index, field confinement, and propagation length of the fundamental mode supported by it are calculated at the telecom wavelength λ = 1.55 μm for different dimensions of a polymer ridge (with the refractive index of 1.535) placed on a gold film surface. The waveguide structure is found to exhibit 23% increase of the propagation length while showing similar confinement as compared to conventional rectangular DLSPPW when ridge thickness t < 450 nm (ridge width w = 600 nm) and ridge width w < 320 nm (ridge thickness t = 600 nm).     

Tight focusing with a binary microaxicon

Using a near-field scanning microscope (NT-MDT) with a 100 nm aperture cantilever held 1 μm apart from a microaxicon of diameter 14 μm and period 800 nm, we measure a focal spot resulting from the illumination by a linearly polarized laser light of wavelength λ=532 nm, with its FWHM being equal to 0.58λ, and the depth of focus being 5.6λ. The rms deviation of the focal spot intensity from the calculated value is 6%. The focus intensity is five times larger than the maximal illumination beam intensity.     

Temperature dependence of spin pumping in YIG/NiOx/W multilayer

We report the temperature dependence of the spin pumping effect for Y₃Fe₅O₁₂ (YIG, 0.9 μm)/NiO (t_NiO)/W (6 nm) (t_NiO = 0 nm, 1 nm, 2 nm, and 10 nm) heterostructures. All samples exhibit a strong temperature-dependent inverse spin Hall effect (ISHE) signal I_c and sensitivity to the NiO layer thickness. We observe a dramatic decrease of I_c with inserting thin NiO layer between YIG and W layers indicating that the inserting of NiO layer significantly suppresses the spin transport from YIG to W. In contrast to the noticeable enhancement in YIG/NiO (t_NiO ≈ 1-2 nm)/Pt, the suppression of spin transport may be closely related to the specific interface-dependent spin scattering, spin memory loss, and spin conductance at the NiO/W interface. Besides, the I_c of YIG/NiO/W exhibits a maximum near the T_N of the AF NiO layer because the spins are transported dominantly by incoherent thermal magnons.     

溶胶-凝胶法制备SiO2-TiO2平板光波导工艺研究

采用溶胶-凝胶法制备了SiO₂-TiO₂平板光波导,计算了平板光波导通光条件,分析了硅/钛溶胶-凝胶材料的热性能,观测了平板光波导的结构形貌,并测试了其通光损耗。结果表明：经过200℃,30 min干燥处理的凝胶薄膜呈疏松多孔状态,对于非对称平板波导,存在芯层通光截止厚度,而且当SiO₂-TiO₂芯层厚度为0.5 μm时,SiO₂下包层厚度至少有6 μm才能防止1550 nm波长光泄露入单晶硅衬底中。制备的光波导对于1550 nm波长光传输损耗最小值为0.34 dB/cm。     

1.55μmSi_(1-x)Ge_x光波导与Si_(1-x)Ge_x/Si多量子阱探测器集成的优化设计

对１．５５μｍ波长的Ｓｉ１－ｘＧｅｘ光波导和Ｓｉ１－ｘＧｅｘ／Ｓｉ多量子阱（ＭＱＷ）红外探测器的集成器件结构进行了系统的分析和优化设计。优化结果为：１）对Ｓｉ１－ｘＧｅｘ光波导，Ｇｅ含量ｘ＝０．０５，脊宽、高和腐蚀深度分别为８、３和２．６μｍ；２）对Ｓｉ１－ｘＧｅｘ／Ｓｉ多量子阱红外探测器，Ｇｅ含量ｘ＝０．５，探测器由厚度为５５０ｎｍ、２３个周期的６ｎｍＳｉ０．５Ｇｅ０．５＋１７ｎｍＳｉ组成，长度约２ｍｍ。结果表明，这种结构器件的内量子效率可达８８％。     

The absorption spectrum of polycrystalline silver halide fibres

The wavelength dependence of the attenuation in polycrystalline AgCl:AgBr fibre has been determined between 2.5 μm and 14 μm. The background attenuation as λ^-2 dependence as expected but there are also strong absorption peaks due to water and silver oxide which, to our knowledge, are observed for the first time in these fibres.     

Nd^3＋：La2Be2O5单晶的光谱特性

Ｎｄ（３＋）：Ｌａ２Ｂｅ２Ｏ５（Ｎｄ（３＋）：ＢＥＬ）是一种具有单斜结构的双轴晶体，发射线性偏振荧光谱，当Ｅ∥Ｘ时，荧光峰值波长为１．０７０μｍ，Ｅ∥ｙ（ｂ）时，＝１．０７９μｍ．本文测量了Ｎｄ（３＋）：ＢＥＬ单晶的吸收谱，偏振和非偏振荧光谱，低温荧光谱（７７Ｋ°）和荧光寿命，（τ＝１３５±５μｓ），并且分析了其光谱特性与Ｎｄ（３＋）：ＹＡＧ作了比较，认为Ｎｄ（３＋）：ＢＥＬ更适合激光二极管泵浦．     

有限包层半径光纤Bragg光栅的理论研究

采用光纤波导三层模型,对有限包层半径光纤Bragg光栅导模有效折射率的改变进行了理论分析,结果表明:当包层直径小于16μm时,单模光纤Bragg光栅(纤芯直径为8.3μm)的导模有效折射率才开始发生明显变化.在包层外添加外包层,通过改变外包层的折射率可以实现对光栅Bragg反射波长的调谐,同时对不同芯子直径的光栅Bragg波长移动进行了数值计算.在保证光纤归一化频率不变的前提下,芯径越小Bragg波长调谐范围越大,当包层厚度为1μm时,芯径为a＝2.2μm的光栅Bragg波长调谐范围约为3.9μm.     

微结构窄带滤光片设计及制备工艺研究

为了提升微结构窄带滤光片的光谱透过率,增大微结构单元的制备精度,提出一种新的膜系镀制方法和微结构单元的制备方法。基于法布里-珀罗(F-P)多光束干涉仪原理设计了3种不同中心波长的窄带滤光片,采用光化学掩模分离法和PECVD技术相结合,制备出3种中心波长分别为480 nm、520 nm和590 nm,峰值透过率均大于80%,半宽度30 nm~50 nm,微结构单元的通道面积为50 μm×50 μm的窄带滤光片。光谱透过率得到了提升的同时微结构单元边缘整齐、分界线清晰,精度也得到了有效地增加,达到μm量级。     

细胞光阱刚度与折射率关系理论计算

为了探讨用光镊技术进行细胞折射率的测量方法,用几何光线理论对可作为米氏粒子模型的生物细胞(半径a=10μm,折射率n=1.35~1.70),在单光束梯度力光阱[激光波长λ=780 nm,功率P=6 mW,焦斑半径w(0)=0.6μm、0.8μm和1.0μm]中的轴向光阱刚度与细胞折射率关系进行了数值计算。结果表明,光阱刚度随折射率的变化关系与三次多项式曲线拟合得较好;用测量光阱刚度计算细胞的折射率时,需要用折射率已知的四种标准粒子对三次多项式曲线进行标定。     

Silver halide single-mode strip waveguides for the mid-infrared

We report the demonstration of single-mode AgCl(x)Br(1-x) strip waveguides for the mid-infrared (MIR). The waveguides were made by the deposition of AgCl(x)Br(1-x) layers on top of a Si-SiO(2) substrate, followed by photolithographic and lift-off processing. The propagation losses of 20 dB/cm were measured at λ=10.6 μm using the cut-back method. The development of these waveguides is a crucial step toward realizing AgCl(x)Br(1-x) MIR integrated optical circuits, which would be used for applications such as chemical sensing and stellar interferometry.     

An optically pumped supersonic iodine beam laser

We report the realisation of an optically pumped I₂-laser using a supersonic beam as active medium. Threshold pump power of the order of 10 mW and output power at λ_d=1.34 μm of up to 2 mW is observed with λ_p=514.5 nm as pump radiation. In contrast to the similar Na₂-beam laser, the output of a ring cavity is bidirectional with a forward to backward intensity ratio of about 10:1.     

Coupling characteristics of high birefringence dual-core As2S3 rectangular lattice photonic crystal fiber

A type of As2S3 chalcogenide glass mid-infrared dual-core photonic crystal fiber has been proposed.The dualcore photonic crystal fiber(PCF) consists of two asymmetric cores.The high polarization property and the coupling characteristics have been studied by using the finite element method and mode coupling theory.Numerical results show that the birefringence at wavelength λ = 10 μm is up to 0.01386 and the coupling length can reach wavelength λ = 5 μm,261 μm and 271.44 μm for x-polarized mode and y-polarized mode,respectively.It demonstrates that a 6.786-mm-long fiber can exhibit an extinction ratio of better than 10 dB and a bandwidth of 180 nm.     

1.30μm／1.55μm SiGe多模干涉滤波器

用多模干涉原理分析和设计了光通信波长（１．３０μｍ～１．５５μｍ）的Ｓｉ１－ｘＧｅｘ／Ｓｉ滤波器，并用模的传播分析方法对其传输特性进行了研究。结果发现，在Ｇｅ含量ｘ＝０．０４时，干涉区的脊高和宽度分别为６．３５μｍ和８μｍ。如果多模干涉区长度ＬＭ＝２３０２．５μｍ，可滤１．３０μｍ而通１．５５μｍ的波长。且具有３１ｄＢ的对比度和０．０１ｄＢ的插入损耗；如果多模干涉区长度ＬＭ＝２５１２．５μｍ，可滤１．５５μｍ而通１．３０μｍ的波长。具有１６ｄＢ的对比度和０．０９ｄＢ的插入损耗。     

Photoionization detection of stimulated Raman scattering on electron transitions of Na in an atomic beam

Stimulated Raman scattering has been experimentally studied by using the process of two-step ionization of a Na atomic beam. A dip that is due to a resonance at a combination frequency corresponding to the forbidden 3S–4S transition of a Na atom was observed in the signal of nonresonant photoionization when two laser frequencies λ₁=284.5 nm and λ₂=1.06 μm were overlapped.     

利用微球层提高有机发光二极管出光效率

采用自组装的方法(提拉法)在普通玻璃盖玻片衬底上制备了聚苯乙烯微球层,对其进行简单的热处理可获得类似微透镜的结构。利用折射率匹配液将其耦合在常规OLEDs的出光面,研究了其对器件光学特性的影响。初步的研究结果表明:热处理后的直径为3μmPS微球层可将限制在玻璃衬底中的部分光耦合到前向外部空间,并将OLEDs器件正方向的发光亮度(效率)提高大约9%。     

Wave propagation in deep-subwavelength mode waveguides

This Letter proposes a dielectric waveguide with deep-subwavelength mode sizes. Results of both frequency domain and time domain analysis show that the effective mode area is below λ(0)(2)/400 and can even reach λ(0)(2)/1000 (λ(0) is the wavelength in vacuum). The effective electrical mode area can be comparable to that of a hybrid plasmonic subwavelength confinement waveguide, with reduced optical absorption. In contrast to slot waveguides, which guide light in low-index materials, the proposed structure guides light in high-index materials. Results obtained in this Letter show that the losses are sensitive to the surface roughness on the tens of nanometers scale. The structure can be used to design ring resonators with a quality factor comparable to that of a diffraction-limited dielectric ring resonator with the same standing wave numbers. The property can be applied in nonlinear effect enhancement or laser design with ultralow threshold.