基于二氧化硅薄膜夹层式亚波长金属光栅的宽波段太赫兹偏振分束器

设计出一种结构新颖的宽波段太赫兹偏振分束器,这种偏振分束器由夹层式亚波长金属光栅制成。亚波长金属光栅偏振分束器可以将入射的任意自然光分成两束偏振状态垂直的线偏振光。其中,TE模反射而TM模透射。设计的偏振分束器在3.5~5.5 THz波段可以达到很高的衍射效率与消光比。但是,在光栅的实际制作过程中,加工技术的缺陷引起的误差大大影响了光栅的性能,比如衍射效率,消光比等。因此文中对一些结构参数进行了计算,从计算结果可以看出这种偏振分束器也有很好的工艺容差。当覆盖层厚度D1与底层介质厚度D3的变化范围分别为1~1.2 m和2.8~3 m时,T0TM大于96.9%,R0TE大于98.7%。Tc和Rc分别大于31 dB和33.4 dB。结果显示,设计的偏振分束器在2 THz的带宽10的大角度范围内,衍射效率高于90%,消光比大于20 dB。因此文中设计对于太赫兹调制器件的研究,以及太赫兹通信系统的集成都有很大的参考价值。     

亚波长偏振光栅的研究进展

亚波长偏振光栅(PGs)具有衍射效率高,偏振特性好,易于实现偏振、分束、增透、高反、相位延迟等多种功能的优点,且体积小、重量轻、性能稳定可靠,是一种优良的新型光学元件,有着巨大的应用前景.介绍了亚波长偏振光栅的发展概况与最新研究进展,亚波长偏振光栅的特点及衍射理论,并分别对会属亚波长偏振光栅和介质业波长偏振光栅进行了分析.     

具有光束偏转功能的亚波长光栅偏振分束器

针对亚波长光栅偏振分束器无法实现垂直出射光 、集成耦合效率低的问题,本文设计了 一种具有光束偏转功能的亚波长光栅偏振分束器,可实现偏振分束且能获得垂直出射光。器 件上 层采用光栅衍射理论设计了可实现偏振分束的周期亚波长光栅,下层通过严格耦合波法与波 前相 位控制理论设计了具有光束偏转功能的非周期亚波长光栅。基于有限元软件COMSOL对设计 的器 件进行仿真分析,结果表明该器件可分开TE与TM混合偏振光且能实现光束垂直出射,两种 偏振 光的总透射率在1550nm处超过了76.5%,偏振 消光比为14.0 dB。因此通过该偏振分束器不但可 以获得垂直出射的单偏振光,而且能有效提高垂直耦合型器件的工作效率,有望应用在面向 光纤通信的集成光电器件中。     

亚波长光栅偏振器的研究现状与发展前景

亚波长光栅偏振器具有体积小、结构紧凑、易于集成,偏振性好的特点,是一种性能优良的衍射光学元件,具有广阔的应用前景。本文总结了多种类型的亚波长光栅偏振器,对每种亚波长光栅偏振器的结构和特点进行了分析和概括,并对亚波长光栅偏振器的前景进行了展望。     

基于晶体双折射和电光效应设计的90°2×4空间光桥接器

综合利用锂酸铌(LiNbO3)晶体的双折射效应和电光效应,设计了一种适用于相干光通信系统的新型空间光桥接器.其由4块结构相同的具有电极控制的晶片和一块检偏双折射元件所组成,两对双折射晶体光学平板利用双折射效应分别实现信号光和本振光的偏振分离和合束,电光调制则产生所需的相移.通过调整晶片的控制电压,可从检偏双折射元件输出四通道的相对相位差为90°的信号/本振合成光.与以往的空间光桥接器相比,该桥接器具有结构紧凑、损耗小和相移性能稳定的优点.     

800 nm亚波长夹层式金属偏振分束光栅

为获得高性能的偏振分束光栅,设计了一种亚波长夹层式金属光栅结构,通过严格耦合波分析和遗传算法优化出最佳光栅结构。所设计的光栅在波长为800 nm时,0级衍射级次上TM偏振波的透射率和TE偏振波的反射率分别为98%和96.5%。在波长747 nm 854 nm,以及入射角-27 27范围内,光栅的透射和反射消光比都大于20 dB,达到了高衍射效率、高消光比、宽带宽及大角度的要求,数值分析表明该光栅对周期、槽深、覆盖层厚度具有优良的工艺容差。该光栅结构简单,性能稳定,对入射光损耗低,偏振分束效果明显,在光学偏振器件、激光器系统、偏振成像等领域具有广泛的应用前景。     

一维深亚波长光栅的耦合波分析及偏振特性的研究

讨论了一种新的一维深亚波长光栅,其周期结构由等离子体增强化学气相淀积法(PECVD)制备的周期性多层膜构成。简单介绍了这种深亚波长光栅的制作方法。采用严格耦合波分析(RCWA)理论计算了这种一维深亚波长光栅的衍射效率,分析了它的偏振特性。     

相干光通信中的光学桥接器

相干光通信技术是提高接收机灵敏度,发展大容量高码率激光通信系统的重要技术手段,光学桥接器将信号激光和本振激光链接到光电探测器进行相干探测处理,是相干光通信系统的关键器件之一.对近20多年来发展的光学桥接器进行了总结和分类,介绍了不同光学桥接器的原理、构造和性能,分析了光学桥接器的关键技术.     

A broad-band waveguide grating coupler with a subwavelength grating mirror

A new diffractive device for light coupling between a planar optical waveguide and free space is proposed. The device utilizes a second-order waveguide grating to diffract the fundamental waveguide mode into two free propagating beams and a subwavelength grating (SWG) mirror to combine the two free propagating beams into a single beam. The finite-difference time-domain (FDTD) simulations show that the SWG mirror improves the coupling efficiency of the waveguide fundamental mode into the single out-coupled beam from about 30% to 92%. A high efficiency (>90%) is predicted for a broad wavelength range of 1520-1580nm. The proposed device is compact (/spl sim/80 /spl mu/m in length) and it eliminates the need for blazing the waveguide grating.     

Design and evaluation of fundamental-mode and polarization-stabilized VCSELs with a subwavelength surface grating

We demonstrate 850-nm oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with a locally etched subwavelength surface grating that are single-mode and polarization stable from threshold up to thermal roll-over, reaching /spl sim/4 mW of output power. The side-mode suppression ratio (SMSR) is >30 dB and the orthogonal polarization suppression ratio (OPSR) is /spl sim/20 dB. Moreover, no distortion of the far-field beam profile is observed as a result of the surface grating. Our numerical calculations show that a carefully designed VCSEL can have a high simultaneous mode and polarization selectivity without a significant increase in loss for the favored fundamental mode with polarization state perpendicular to the grating lines. This indicates characteristics such as threshold current and resonance frequency will not be notably degraded. The calculations also show a low sensitivity to variations in grating etch depth and duty cycle, which relaxes fabrication tolerances. In our experimental parametric study, where the oxide aperture diameter, surface grating diameter, and grating duty cycle were varied, the combined mode and polarization selection was investigated. For an optimum combination of oxide aperture and surface grating diameters of 4.5 and 2.5 /spl mu/m, respectively, the device is found to be single-mode and polarization stable for a broad range of grating duty cycles, from 55% to 75%, with only a small variation in other laser performances, which is in line with theory.     

Symmetrical fully-etched and chirped beam splitter based on a subwavelength binary blazed grating

A novel symmetrical chirped beam splitter based on a binary blazed grating is proposed, which adopts the fully-etched grating structure compatible with the current fabrication facilities for CMOS technology and convenient for integration and manufacture process. This structure can realize nearly equal-power splitting operation under the condition of TE polarization incidence. When the absolutely normal incidence occurs at the wavelength of 1580 nm, the coupling efficiencies of the left and the right branches are 43.627% and 43.753%, respectively. Moreover, this structure has the tolerances of 20 nm in etched depth and 3?in incident angle, which is rather convenient to manufacture facility.     

基于蚁群算法的二维多层亚波长光栅结构设计

提出一种适用于长波红外波段的二维偏振无关亚波长光栅结构。利用对称二维结构消除一维光栅的偏振相关性,增加光通量。提出光栅优化评价函数,将光栅结构参数优化转化为路径寻优问题。最后利用蚁群算法求解最优光栅结构参数。仿真结果表明,提出的二维多层结构在10～13 μm波段具有偏振无关、窄周期、窄带宽、低旁带的优点。提出的优化设计方法收敛速度快,优化后的光谱曲线横电波（TE）和横磁波（TM）偏振方向透射率均达到70%,带宽260 nm。     

940nm VCSEL高折射率对比度亚波长光栅反射镜的设计

研究了一种940 nm GaAs基VCSEL的高折射率对比度亚波长光栅反射镜（HCG）,采用GaAs/AlO_x光栅结构,讨论了TE偏振时光栅结构中各参数对反射光谱的作用规律,分析TE、TM不同偏振时反射镜的结构特点,及形貌误差对高反射带的影响。设计的TE-HCG的高反射带中心为940 nm,在0.888～0.985 μm波长范围内,TE波反射率大于99.5%,TM波反射率低于90%,高反射带宽97 nm,Δλ/λ₀>10%。该反射镜可以与VCSEL采用一次性外延生长技术制作,且具有结构简单,制作容差大,且偏振稳定的优势,不仅有利于改善器件性能,且大大降低VCSEL的制作难度和成本。     

抗反射亚波长光栅的特性研究

利用矢量衍射理论的数值求解方法,研究了亚波长光栅结构参数对反射率的影响,特别是基底厚度对反射率的影响,这些为设计和制作具有优良的抗反射性能的二元光学元件提供了设计依据.     

Tunable polarization maintaining fiber Bragg grating based OSNR monitor

A simple optical performance monitoring scheme based on a tunable polarization maintaining fiber Bragg grating is proposed. The proposed technique measures the in-band optical signal-to-noise-ratio through orthogonal polarization detection. The scheme is successfully demonstrated for NRZ-OOK signals at 10 Gb/s with an input dynamic range of around 20 dB. The results show that the performance of the scheme is not sensitive to the effects of chromatic dispersion.     

基于偏振干涉的光纤光栅无线传感网络系统

将光纤光栅传感与无线传输相结合,建立传感节点光路结构理论模型,分析了结构参数对光纤环镜(FLM)特性的影响。以数学模型为依据,优化了S-MAC协议的工作时间、休眠时间等参数,时延和能耗都有很好的改善。设计了基于保偏结构的光纤光栅无线传感网络(WSN)和基于LabVIEW的参数测定软件、解调系统监控软件。参数测定软件使得系统脱离实验室进入应用领域;对无线网络传输结构和S-MAC协议优化的研究为网络节点的可移动和可重布提供了保障。     

三角形面形亚波长光栅的衍射特性研究

运用等效介质法 (EMT)和基于严格电磁场理论的傅立叶模式理论 (FMT)分别讨论了三角形浮雕型的亚波长位相光栅的衍射特性 ,并对以上两种方法的数值模拟结果进行了比较研究。发现了等效介质法的局限性 ,并且利用模式理论研究了导模共振异常现象