Influence on Multimode Rectangular Optical Waveguide Propagation Loss by Surface Roughness

Optical scattering loss coefficient of muhimode rectangular waveguide is analyzed in this work. First, the effective refrac tive index and the mode field distribution of waveguide modes are obtained using the Marcatili method. The influence on scattering loss coefficient by waveguide surface roughness is then analyzed. Finally, the mode coupling efficiency for the SMFOpticalWaveguide （SOW） structure and MMFOptical Waveguide （MOW） structure are presented. The total scatter ing loss coefficient depends on modes scattering loss coeffi cients and the mode coupling efficiency between fiber and waveguide. The simulation results show that the total scatter ing loss coefficient for the MOW structure is affected more strongly by surface roughness than that for the SOW struc ture. The total scattering loss coefficient of waveguide decreas es from 3.97 x 10^-2 dB/cm to 2.96 x 10^-4 dB/cm for the SOW structure and from 5.24 - 10^-2 dB/cm to 4.7 x 10^-4 dB/ cm for the MOW structure when surface roughness is from 300nm to 20nm and waveguide length is 100cm.     

A novel structure of silicon-on-insulator microring biosensor based on Young's two-slit interference and its simulation

A novel silicon-on-insulator microring biosensor based on Young’s twoslit interference has been demonstrated. The transducer signal from electric field intensity distribution on the interference screen is given by using the transfer matrix method(TMM) and two-slit interference principle.The result shows that the structure we propose is advantageous for sensing as the interference pattern is very sensitive to the ambient refractive index around the microring.A small perturbation in refractive index around the microring△n_c will result in a notable shift of destructive interference points(DIPs) on the interference screen.By detecting the shift of the DIPs,the ambient refractive index change can be obtained.     

A novel polarizer based on directional coupler and surface plasmon polaritons

A novel polarizer with a silver nanoribbon added into a traditional waveguide directional coupler is designed to realize the polarized output of TE mode. A high extinction ratio can be obtained because of the selectivity of surface plasmon polaritons （SPPs） on polarization. The effects of the polarizer parameters on coupling efficiency and extinction ratio are discussed. Simulation results indicate that the coupling efficiency for TE mode can reach about 95%, but only 3% for TM mode, with the extinction ratio of TE mode about 15 dB when the light wavelength is 1550 nm, The polarizer may have potential applications in photonic integrated circuits and quantum information technology.     

Extraction of optimized parameters for Si0.6Ge0.4 material and SPP mode propagation through Si0.6Ge0.4/Ag/Si0.6Ge0.4 waveguide

The Lorentz model and modified Debye model （MDM） parameters forSi0.6Ge0.4 are presented. A nonlinear optimiza- tion algorithm is developed. The obtained parameters are used to determine the complex relative permittivity of Si0.6Ge0.4, and compared with the experimental data for validation. Finally the obtained parameters are used to analyze the properties of symmetric surface plasmon polariton （SPP） mode propagation in a dielectric-metal-dielectric （DMD） material constructed with silver （Ag） and Si0.6Ge0.4 for further verifying the extracted parameters.     

Design and experimental research on a visible-near infrared spatial modulating Fourier transform spectrometer based on micro multi-step mirrors

A type of spatial modulating micro Fourier transform spectrometer （FTS） based on micro multi-step mirrors （MMSMs） is designed and manufactured in this paper. The interference system is based on Michelson interferometer, using two MMSMs instead of plane mirrors in two arms. The recovered spectrum is simulated with different distances between MMSMs and the detector, and the influence of diffraction on the recovered spectrum is analyzed. The edge-enlarging method for the MMSMs is proposed to eliminate edge noise, and the influence of surface roughness of MMSMs on the recovered spectrum is also analyzed. Moreover, the way of manufacturing the MMSMs is investigated.     

Development of three-dimensional profiler for large field micro-surface topography measurement

This paper presents a large field phase-shifting interference microscope for micro-surface topographymeasurement. A PZT is used as the Z-directional phase shifter. The interference microscope is the combination of the infinity tube microscope with the Mirau two-beam interferometer. Two-dimensional precision motorized stage is aligned as the scanning system in theX- and Y-direction to extend the test surface measurement range to 12.5 mm× 12.5 mm. The minimum displacement is 0.039 μm and the overlapped proportion is 0.22. A fast stitching algorithm is proposed based on grid matching. According to the reflectivity of the core and the ferrule, the plate with the transmission/reflectivity ratio of 70/30 is selected to balance the interference intensity. The instrument is proved to be valid by actual measurement of the end surface of an optical fiber connector.     

A relocatable resonant FBG-acoustic emission sensor with strain-insensitive structure

A novel resonant fiber Bragg grating （FBG） based acoustic emission （AE） sensor with relocatable, strain-insensitive and enhanced sensitivity structure is demonstrated for structure health monitoring （SHM） in this paper. With one end of the sensing FBG bonded to a polyimide （PI） plate acoustically the other end free, the sensor can be easily redeployed around coupled with the investigated structure via couplant and the monitored structure surface and get rid of the interference from the strain applied on the monitored structure. Experiment has been conducted to verify the characteristics of this FBG-AE sensor, whose results show that the sensor is insensitive to mechanical strain applied on the monitored structure. It is also shown experimentally that the sensitivity is enhanced by about 1.2 times than the conventiotlal design, while the novel sensor possesses good resonant frequency response to the standard AE waves.     

Design of an ultra-compact 3 dB MMI coupler

The design of an ultra-compact SOI-based 1×2 3 dB multimode interference（MMI） coupler is proposed.The symmetric multimode interference structure and deeply-etched parabolically tapered multimode waveguide are used in the device.The length of the device is reduced by about 87% compared with general multimode interference straight couplers.Based on effective index method（EIM） and two dimensional beam propagation method（2D-BPM）,the structure parameters are optimized and the fabrication tolerances are analyzed.The results indicate that the performance of the coupler is deeply affected by the coupler＇s width,etching depth and photolithography alignment error in perpendicular direction.     

大面积非光刻纳米电极间隙的制备

A lithography-independent and wafer scale method to fabricate a metal nanogap structure is demonstrated. Polysilicon was first dry etched using photoresist （PR） as the etch mask patterned by photolithography. Then, by depositing conformal SiO2 on the polysilicon pattern, etching back SiO2 anisotropically in the perpendicular direction and removing the polysilicon with KOH, a sacrificial SiO2 spacer was obtained. Finally, after metal evaporation and lifting-off of the SiO2 spacer, an 82 nm metal-gap structure was achieved. The size of the nanogap is not determined by the photolithography, but by the thickness of the SiO2. The method reported in this paper is compatible with modern semiconductor technology and can be used in mass production.     

近红外波长下COMSOL软件实现新型耦合器的设计

一直以来条状表面等离子波导被认为是实现高集成光路的有效器件,首先采用经典的Drude模型对条状波导中SPP激发与传播特性完成了分析。针对可见光到近红外入射波长的条件完成了条状SPP波导的模场分布的研究,得出,当金属的厚度不变宽度越大,电磁场分布就越集中在条状波导的两侧;当金属条状的宽度不变,厚度越大时电磁场分布会越集中在金属内;入射波长越长会使得金属条状周围电场的集中越小,且还会导致信道间的干扰。利用得到的条状波导特性进而设计了一种新型的耦合器,器件设计结果表明:条状SPP波导在有限传输距离上能量完全转移只发生一次;波长较长时,场的集中度减小,耦合增强;条状SPP波导耦合器可以实现1310 nm和1550 nm的光波分复用。这一研究对光子器件的发展有一定的理论和实际意义。     

银纳米线表面等离子体波导的传输损耗特性研究

通过远场聚焦光斑激发银纳米线表面等离子体激元(SPP: Surface Plasmon Polariton),并搭建银纳米线路由传输结构改变SPP的传输距离,研究了SPP的传输损耗特性。实验上测量了置于玻璃衬底表面的银纳米线在不同激发波长时SPP的传输损耗系数,发现SPP的传输损耗具有波长依赖性：632.8nm激光激发时,传输损耗系数为0.115 ,780nm激光激发时,传输损耗系数为0.0923 ,即传输损耗系数在长波激发时小,而在短波激发时大。测量结果对基于银纳米线波导的集成微纳光学系统设计有很好的指导作用。     

表面等离子体透射增强提高光刻分辨率的模拟

讨论了表面等离子体透射增强现象在提高分辨率上的应用,数值模拟结果显示采用这种方法光刻的分辨率可以达到32nm。首先用FDTD法模拟了一维周期光栅结构的电场场强的分布,光栅模版具有三角形的脊,整个模版覆盖了一层Ag,然后讨论了三角形底角角度变化对透射率和分辨率的影响。当角度在57°～64°之间变化时,得出三角形脊部有透射增强现象产生,最大透射振幅是入射光的4.2倍,分辨率为(30±5)nm。因为凹槽部分透射光强度很小,因此具有很好的分辨率。通过对比周期和非周期边界条件模拟,三角形脊的形状是产生透射增强现象的原因。     

High Contrast Superlens Lithography Engineered by Loss Reduction

Although sub‐diffraction‐limit‐resolution optical imaging has been attained via superlenses in the UV regime, the corresponding resist profile in general exhibits a very poor contrast, far below the minimum requirement for photolithography. Here, it is experimentally demonstrated thin flat silver superlenses, engineered through refining interfacial roughness to reduce scattering loss, capable of resolving grating features of sub‐50 nm resolution with a high contrast of about 2.2. The seed layer effect on the superlens performance at a wavelength of 365 nm has been probed through both experimental and analytical methods. The performance of Ag, Ag/Ni and Ag/Ge superlenses agrees well with theoretical predications. The results show that a smooth interface is a key factor for realizing high performance superlensing, while damping losses become dominant when the roughness is reduced to less than 2 nm. This work verifies that a superlens is a potential tool for sub‐diffraction limit nano‐photolithography.     

MDM光波导激发高阶SPP模的传输特性

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。     

MIM 结构中腔的物理性质对SPP传播的分析

为了研究MIM 结构中腔的物理性质对SPP 传播的影响,采用了对波导模式、谐振和反射系数以及相位分析的理论方法,讨论了腔长和厚度对SPP 传播的相关参数的影响,仿真了MIM 波导中电动势、腔长和反射系数等参数在结构中作用.结果表明,SPP 传播产生的电动势能达到相对较大的1V,激发产生的能场会有放大的作用;腔的有效功率变化与腔长变化一致,不同的腔厚度中腔长对SPP 传播的结果趋势相同;近场中传播系数存在一个最大值.这一问题的分析与讨论对非线性THz光谱研究、纳米级光电探测、SPP 模式的发生器、强局域场都具有一定的意义.     

KrF光刻工艺技术

比较了248nm KrF光刻工艺与i-Line工艺上的异同,利用工艺原理和光学原理分析了248nm KrF光刻工艺的特点.对一些光刻工艺中容易出现的问题进行了探讨,使248nm KrF光刻技术在实际工艺中可以得到灵活应用.     

任意拓扑荷光学旋涡的产生及应用

光学旋涡在很多领域开展了广泛的研究和应用。介绍了一种基于涡旋波片的光学旋涡产出方法,并通过波片组合的方法可以产生任意拓扑荷的光学旋涡,该方法具有很好的灵活性。同时由于波片的透过率非常高,实验中拓扑荷为3 的光学旋涡的产生效率高达93%以上。通过干涉产生的叉形光栅叉数和方向进一步检测了产生光学旋涡的拓扑荷。利用产生的光学旋涡还进行了初步的光学操控实验,验证了轨道角动量对于微颗粒的动态操控作用。该方法将在更多领域得到推广和应用。     

Plasmonic Modulation of Valleytronic Emission in Two-Dimensional Transition Metal Dichalcogenides

Monolayered transition metal dichalcogenides (TMDs) are one kind of hexagonal 2D semiconductors with a direct bandgap structure. Due to the property of natural broken inversion symmetry in the lattice, the strong spin–orbit coupling of electrons in TMDs can induce degenerate levels with antiparallel spins in K and K′ valleys, which selectively respond with external light excitations. Surface plasmon resonance with efficient electromagnetic enhancement and near-field coupling provides excellent potential opportunities to modulate valley emission of TMDs. Efforts have been devoted to investigating the interaction principles and applications of this research field. This review focuses on plasmonic modulation of valleytronic emission in TMDs with surface plasmon polaritons (SPP) and localized surface plasmons (LSP) based on different modulation principles, respectively, and discusses possible research directions for future device applications.