Surface Plasmon Interference Lithography Assisted by a Fabry-Perot Cavity Composed of Subwavelength Metal Grating and Thin Metal Film

A surface plasmon interference lithography assisted by a Fabry-Perot （F-P） cavity composed of subwavelength metal gratings and a thin metal fihn is proposed to fabricate high-quality nanopatterns. The calculated results indicate that uniform straight interference fringes with high contrast and high electric-field intensity are formed in the resist under the F-P cavity. The analyses of spatial frequency spectra illuminate the physical mechanism of the formation for the interference fringes. The influence of the F-P cavity spacing is discussed in detail. Moreover, the error analyses reveal that all parameters except the metal grating period in this scheme can bear large tolerances for the device fabrication.

Study on tapered crossed subwavelength gratings by Fourier modal method

Fourier modal method incorporating staircase approximation is used to study tapered crossed subwavelength gratings in this paper. Three intuitive formulations of eigenvalue functions originating from the prototype are presented, and their convergences are compared through numerical calculation. One of them is found to be suitable in modeling the diffraction efficiency of the circular tapered crossed subwavelength gratings without high absorption, and staircase approximation is further proven valid for non-highly-absorptive tapered gratings. This approach is used to simulate the ＂moth-eye＂ antireflection surface on silicon, and the numerical result agrees well with the experimental one.

Resonant Effects of FPL and SPP for Light Transmitting through Subwavelength Metallic Gratings

A new model is proposed to explain the physical mechanism of the extraordinary transmission enhancement in subwavelength metallic grating.The extraordinary transmission enhancement is described by the co-operation of Fabry-Perot-like(FPL) resonance and the surface plasmon polariton(SPP) resonance.The rigorous coupled-wave analysis(RCWA) and the finite difference time domain(FDTD) method are employed to illustrate the model by calculating the transmission and the field distributions in the subwavelength metallic grating,respectively.And the numerical calculations show that transmission enhancement is achieved when the coupling resonance of the incident light,the surface plasmon polariton mode and the Fabry-Perot-Like mode is happened,which are in good agreement with the proposed model.

亚波长光栅与法布里-珀罗滤光片集成的高性能光谱偏振分光器

光谱偏振成像技术是一种新型的光学成像技术,它不仅提高了目标的信息获取量,还降低了背景噪声,可以捕获目标细节,检测伪装目标。本文提出了一种将亚波长光栅与F-P滤光片相结合的光谱偏振测量器件,该器件可以获得超高光谱分辨率和偏振消光比,并且光谱和偏振可以灵活调控。本文设计了一种光谱偏振同时分光器,可同时获得4个光谱通道的斯托克斯参数。仿真结果表明,其光谱分辨率为217,偏振消光比为106。实验结果表明,亚波长光栅的偏振消光比大于500,透射率为90%。全介质F-P滤光片的光谱分辨率为30,在长波红外波段的透射率为60%。该设计方法具有通用性,可用于可见光、红外甚至太赫兹等波段。得益于这些优点,器件在微型偏振光谱仪和全斯托克斯偏振检测等领域有很大的应用潜力。

光栅干涉式触觉传感器

因光学式触觉传感器有着灵敏度高、抗干扰能力强等优点,提出了一种基于亚波长金属光栅干涉的触觉传感器。首先,基于等效介质理论和薄膜干涉理论对触觉传感器的传感原理进行介绍;接着,通过纳米压印工艺和真空蒸发镀膜工艺在柔性中间聚合物片材(IPS)表面制作亚波长金属光栅,通过光刻工艺用SU—8光刻胶将亚波长金属光栅以固定间距平行离面放置,使其透射光强随接触力的施加而改变;最后,对光栅触觉传感器进行一系列力加载实验,实验结果表明:该触觉传感器的平均力分辨率可达到0.0003N/Gray以上,平均测量误差为6.3%。通过小型化设计,可以用于机械手上实现触觉传感功能。

基于对称破缺的导模共振耦合超窄带滤波器设计

为实现超窄带滤波器在光通讯、光传感领域的应用需求,本文提出了一种在非对称光栅波导结构中引入耦合导模共振,来完成对特定波长进行高效传输滤波。该滤波结构由集成在硅基波导上的两个具有同周期但不同填充因子的堆叠亚波长光栅构成。光从堆叠光栅中的顶部垂直入射,通过调节底部光栅的厚度和填充因子,可激发多波导模式的非对称共振耦合。仿真结果表明,利用该对称破缺导模共振耦合原理,在满足高边带抑制比的前提下,产生极强的电场增强,不仅能实现0.005nm的超窄带滤波效果,而且还具有很高的传输效率,可达到99%。

基于亚波长光栅辅助定向耦合器的集成铌酸锂偏振分束器

绝缘体上铌酸锂(LNOI)是实现高速光子集成回路(PICs)的理想平台。通过充分利用铌酸锂(LN)的优势,LNOI平台能够实现高速电光和高效非线性光学集成器件。偏振分束器(PBS)作为分离和组合两种正交偏振光模式的关键无源器件之一,在实现片上偏振复用系统并提升光通信系统数据传输容量方面发挥着至关重要的作用。近年来,基于不同结构的PBS已经被成功实现,其中,基于亚波长光栅辅助定向耦合结构的PBS表现出优异的器件性能和紧凑的器件尺寸。本文基于氮化硅-铌酸锂异质集成的间接刻蚀方案,实现了一种亚波长光栅辅助定向耦合结构的高性能PBS。仿真结果表明,当波长在1500~1600 nm时,器件的偏振消光比均大于24.49 dB。实验数据进一步证实,当波长在1500~1580 nm时,器件偏振消光比均大于18.06 dB。

Novel Even Beam Splitters Based on Subwavelength Binary Simple Periodic Rectangular Structure

In this paper, a novel method of a subwavelength binary simple periodic rectangular structure is presented to realize even beam splitting by combining the rigorous couple-wave analysis with the genetic algorithm. Several even splitters in the terahertz region were designed and one of the silicon-based beam splitters designed to separate one incident beam into four emergent beams has total efficiency up to 92.23 %. Zero-order diffraction efficiency was reduced to less than 0.192 % and the error of uniformity decreased to 6.51 9 10-6. These results break the limitation of even beam splitting based on the traditional scalar theory. In addition, the effects of the incident angle, wavelength, as well as the polarizing angle on the diffraction efficiency and uniformity were also investigated.

Microtrap on a concave grating reflector for atom trapping

We propose a novel scheme of optical confinement for atoms by using a concave grating reflector.The two-dimension grating structure with a concave surface shape exhibits strong focusing ability under radially polarized illumination.Especially,the light intensity at the focal point is about 100 times higher than that of the incident light.Such a focusing optical field reflected from the curved grating structure can provide a deep potential to trap cold atoms.We discuss the feasibility of the structure serving as an optical dipole trap.Our results are as follows.（i） Van der Waals attraction potential to the surface of the structure has a low effect on trapped atoms,（ⅱ） The maximum trapping potential is ~1.14 mK in the optical trap,which is high enough to trap cold ^87Rb atoms from a standard magneto-optical trap with a temperature of 120 μK,and the maximum photon scattering rate is lower than 1/s.（ⅲ） Such a microtrap array can also manipulate and control cold molecules,or microscopic particles.

可见光宽入射角度金属偏振分束光栅的消光比特性研究

设计出一种工作在可见光波段宽入射角度范围具有高消光比的金属偏振分束光栅。采用等效介质理论对金属偏振分束光栅原理进行定性分析,利用严格耦合波理论和时域有限差分法对金属Al光栅进行数值仿真并详细分析了结构参数中周期、高度以及光波长和入射角度等参数对偏振特性的影响。结果表明:当Al光栅占空比为0.5,周期为0.15μm,光栅脊高度为0.15μm时,在0.4~0.7μm波段和45°±10°入射角范围内,该金属偏振光栅对TM波高透射,对TE波高反射,光栅透射消光比平均35 dB,反射消光比平均12 dB,最后对制作的金属偏振光栅进行消光比测量,验证了设计结果的正确性。该研究结果对设计和制备高衍射效率、高消光比、宽波段宽入射角度范围的偏振分束器具有较好的实践指导价值。

基于双层金属光栅的高消光比高透过率太赫兹偏振器

本文设计了一种基于双层金属亚波长光栅的太赫兹偏振器,其可以实现高透过率和良好消光比的特性.该偏振器是通过微加工技术在薄石英衬底的上下表面上制备而成的.实验和模拟结果均表明,双层金属光栅具有与单层金属光栅相近的透过率、更高的偏振度和更高的消光比.在0.3~2.0 THz的频率范围内,测量的透过率在83.4%到62.7%之间,偏振度大于99.7%,消光比大于29 dB.此外,设计的两种双层金属光栅偏振器件成功地应用于太赫兹时域光谱(TeraHertz Time Domain Spectroscopy,THz-TDS)系统中,获得了超过96.2%的偏振度和超过17.1 dB的消光比.通过调整金属亚波长光栅的参数(例如间距、线宽和金属膜厚度),可以进一步提高透过率、偏振度和消光比等特性.

基于硅基砖砌型亚波长光栅的紧凑型模式转换器

亚波长光栅可以等效为均匀介质,具备可控的双折射、色散和各向异性等优势,有利于设计高性能的光子器件.尽管目前传统的亚波长光栅结构只需要单步刻蚀,然而通常需要100 nm及以下的制造分辨率,这对当前主流的晶圆级硅光子芯片制造技术来说比较困难.亚波长光栅的各向异性可以通过引入砖砌型拓扑结构来进一步设计,从而在设计中提供额外的自由度,同时还可以降低制造分辨率需求(>100 nm).本文提出并研究了基于硅基砖砌型亚波长光栅的紧凑型TE_(0)-TE_(1)和TE_(0)-TE_(2)模式转换器,其中砖砌型亚波长光栅的最小特征尺寸为145 nm.实现了TE0模式到TE1模式和TE_(2)模式的转换,转换区域长度分别为9.39μm和11.27μm.测试结果表明,在68 nm(1512-1580 nm,受限于激光器调谐范围和光栅耦合器)带宽内,插损和串扰分别小于2.5 dB和-10 dB.

基于亚波长光栅的高性能定向耦合器的研究

在SOI平台上提出并设计了一种基于亚波长光栅(SWG)和非对称耦合型(ADC)波导的高带宽低损耗的定向耦合器。SWG结构嵌入在两条波导之间,可以有效提高TE模式的耦合强度。通过优化分析选择器件参数,并通过调整耦合区长度实现了不同功率分束比,包括50%/50%、60%/40%、70%/30%、80%/20%、90%/10%。在不同分束比下带宽均超过100 nm,插入损耗均小于0.3 dB,部分分束比下带宽大于150 nm,插入损耗小于0.2 dB。器件最小耦合区尺寸仅为7.4μm×1.2μm。

Research on photodiode integrated with wide spectrum focusing reflector using nonperiodic subwavelength gratings

The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental results show that the gratings can reflect and focus the incident light on the absorber of the photodiode, and thus can simultaneously achieve high speed and high efficiency. For the gratings’ integrated photodiodes, the responsivity is improved over a wide spectral range, and when the absorber was 600 nm and the mesa diameter was40 μm, a responsivity of 0.46 A/W at a wavelength of 1.55 μm and a 3 dB bandwidth of 21.6 GHz under a reverse bias of 3 V were simultaneously obtained.

Suspended nanomembrane silicon photonic integrated circuits

Leveraging the low linear and nonlinear absorption loss of silicon at mid-infrared(mid-IR)wavelengths,silicon photonic integrated circuits(PICs)have attracted significant attention for mid-IR applications including optical sensing,spectroscopy,and nonlinear optics.However,mid-IR silicon PICs typically show moderate performance compared to state-of-the-art silicon photonic devices operating in the telecommunication band.Here,we proposed and demonstrated suspended nanomembrane silicon(SNS)PICs with light-guiding within deep-subwavelength waveguide thickness for operation in the short-wavelength mid-IR region.We demonstrated key building components,namely,grating couplers,waveguide arrays,micro-resonators,etc.,which exhibit excellent performances in bandwidths,back reflections,quality factors,and fabrication tolerance.Moreover,the results show that the proposed SNS PICs have high compatibility with the multi-project wafer foundry services.Our study provides an unprecedented platform for mid-IR integrated photonics and applications.

亚波长介质光栅的制作误差分析

利用严格耦合波理论 (RCWA )分析了方向误差和面形误差对亚波长光栅衍射效率的影响 通过分析发现 ,方向误差和图案边缘钝化对光栅的衍射效率影响不大 ,而刻蚀过程中由于侧壁倾斜而产生的面形误差对光栅的衍射效率影响非常大 在制作亚波长光栅时 ,可以通过选取合理的刻蚀系统或增大占空比的方法来避免基底型误差的出现 该结论对于制作亚波长光栅具有重要的指导作用 同时根据得出的结论 ,选用专门用于硅深刻蚀的等离子体辅助刻蚀系统制作出了红外30 μm亚波长抗反射光栅 ,检测结果显示 。

基于超材料的中波红外宽带偏振转换研究

基于硅纳米块阵列和亚波长金属光栅,硅纳米块长轴与金属光栅夹角为45°,本文设计了一种高效、宽带偏振转换结构.模拟计算表明该结构实现了线偏振光90°旋转,在3.4—4.5μm波段偏振转换率大于60%,在3—5μm光谱范围内的转换对比率大于10~4.由于该结构光学性能优异,制备难度低,可以应用于光传输控制.

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。

亚波长金属光栅的衍射辐射特性研究

分析了亚波长金属光栅的双边衍射辐射机制和特性.利用运动电子激励亚波长光栅结构,研究了其产生的双边衍射辐射.通过三维粒子模拟软件仿真,得到了光栅上下空间的电场空间分布,结合结构辐射布里渊图,证明了亚波长对称光栅上下半空间的衍射辐射场分布同样可以由Smith-Purcell辐射公式来解释,即主要有电子运动速度和光栅周期决定,并分别研究了缝隙宽度、光栅厚度对上下半空间衍射辐射的影响.为进一步研究下半空间的衍射辐射场,采用了非对称的光栅结构,研究表明非对称光栅下半空间衍射辐射场不仅取决于电子运动速度和结构下表面的周期,同时也与电子运动激励起的上半空间的辐射频率范围密切相关.

基于导模共振效应提高石墨烯表面等离子体的局域特性

本文构建了一种包含石墨烯和亚波长光栅的复合结构,借助衍射光栅的导模共振效应,在石墨烯表面激发高局域性表面等离子体激元,研究了石墨烯与光栅结构对表面等离子体激元局域特性的影响规律,并借助基于有限元法的COMSOL软件,分析了缓冲层厚度、光栅周期、载流子迁移率和费米能级对石墨烯的表面电场、品质因子Q和有效模式面积Seff的影响.结果表明,石墨烯表面等离子体激元的局域性在特定的参数点获得显著提高:当μ=0.7 m^2/(V·s)时,品质因子达到最大值Q_(max)=1793;当p=235 nm或E_F=0.72eV时,表面电场达到了入射光的3000倍以上.强烈的局域性导致强烈的光-物质相互作用,因而本文提出的复合结构可实现高灵敏度传感器和高效率的非线性光学设备,极大地扩展了石墨烯在纳米光学领域中的应用.