Analysis and Simulation of S-shaped Waveguide in Silicon-on-insulator

The simulation and analysis of S-shaped waveguide bend are presented.Bend radius larger than 30 mm assures less than 0.5 dB radiation loss for a 4-μm-wide silicon-on-insulator waveguide bend with 2-μm etch depth.Intersection angle greater than 20° provides negligible crosstalk (<-30 dB) and very low insertion loss.Any reduction in bend radius and intersection angle is at the cost of the degradation of characteristics of bent waveguide and intersecting waveguide, respectively.     

Characteristics of S-shaped waveguide structures by the annealedproton exchange process in LiNbO3

The loss of S-shaped waveguide bends in annealed proton-exchanged LiNbO₃ integrated optical devices is found to be dependent on the length of thermal annealing time. The minimum transition length required in order to have losses as low as 0.2 dB is 2.0 mm for a 0.1-mm lateral offset. Intersecting waveguides based on S-shaped structures have been characterized for passive crossovers. An angle greater than 6° is required to provide a crosstalk of less than -30 dB. At a particular angle, intersecting waveguides offer the possibility of making a 3-dB coupler if an insertion loss of 1.2 dB is not a big concern. Zero-gap couplers based on S-shaped structures have been characterized for applications as 3-dB couplers as well. This type of 3-dB coupler has a much lower insertion loss of roughly 0.4-0.5 dB. Both 3-dB intersecting waveguides and 3-dB zero-gap couplers are less sensitive to wavelength variations     

Ti:LiNbO3 intersecting waveguides

Experimental crosstalk and insertion loss characteristics of Ti: LiNbO3 intersecting channel waveguides are presented. A single-?n intersection region is used. The characteristics of both TE and TM are presented for angles of 2?20°. Our aim was to determine the minimum angle required to produce negligible loss and crosstalk (< ? 35 dB) when signals are routed across one another in switching architectures.     

Compact and low-loss arrayed waveguide grating module with tolerance-relaxed spot-size converter

A compact, low-loss arrayed waveguide grating (AWG) module was achieved by adopting a novel optical spot-size converter (SSC) to planar lightwave circuits (PLCs). The SSC is a laterally tapered waveguide that can be fabricated simply by the conventional fabrication process. The structure is composed of a core width converting region where the spot-size is converted efficiently, and a core width fine-tuning region where the cut-position tolerance is relaxed. We have applied this structure to a 1.5%-/spl Delta/ silica-based waveguides and reduced the single-mode fiber coupling loss to less than 0.5 dB/point. The SSC provides a large cut-position tolerance that enables angle polishing of the PLC endfaces to prevent reflection and low-loss connection of pigtail fibers. The center channel insertion loss of the AWG module was reduced from 4.2 to 2.2 dB, and the reflection was less than -60 dB.     

硅基光子材料和器件的进展

评述硅基光子材料和器件的进展,包括硅二极管的受激发射、具有量子结构的RCE(谐振腔增进型)光电二极管、MOS高频光调制器、SOI光开关阵列和可调谐波长滤波器,重点介绍低插入损耗、快响应的SOI基热光波导开关阵列的最新结果.以SOI为基片,成功地研制出带有全内反射(TIR)镜的重排无阻塞型光开关阵列,并首次研制出16×16阻塞型光开关阵列.在1.55μm波段,插入损耗和偏振相关性随着器件长度的增加而略微增大.如果器件的末端镀上抗反射膜,插入损耗会降低2～3dB,这些器件的上升和下降时间分别为2.1和2.3μs.     

多口三环CSRR微带低通滤波器的研究与设计

提出一种新型的多口三环CSRR结构,利用CSRR谐振器的单极点低通特性和环与微带线之间的耦合,构成低通滤波器.分析该结构的等效电路模式,指出谐振频率的计算公式.使用HFSS适当优化参数,可以得到性能良好的低通滤波器.其-3 dB截止频率8.76 GHz,通带内插入损耗小于0.3306 dB,通带内回波损耗小于-13.810 2 dB,衰减15 dB以上阻带带宽达到10.31 GHz.为了改善通带内的回波损耗,在微带线两侧加载并联开路枝节.其-3 dB截止频率8.385 GHz,通带内插入损耗小于0.174 7 dB,通带内回波损耗小于-19.707 7 dB,衰减15 dB以上阻带带宽达到10.7 GHz.     

波导带通滤波器与微带转换装置的设计

利用三维仿真软件HFSS首先设计了K波段7阶电感E面带通波导滤波器,以及波导-微带转换器.其中波导滤波器的中心频率为19 GHz,带宽为3 GHz,带内损耗小于0.1 dB,端口反射小于-20 dB;而波导-微带的转换器在16～20.8 GHz的带宽内端口反射小于-20 dB,带内损耗小于0.1 dB.然后将两者有效结合为一体,其工作带宽为17.5～20.5 GHz,带内损耗为0.3 dB,端口反射小于-15 dB,带外抑制小于-30 dB,可以满足实际系统应用的需求.     

2×2 optical waveguide switch with bow-tie electrode based oncarrier-injection total internal reflection in SiGe alloy

Based on the total internal reflection and the plasma dispersion effect of SiGe alloy, a 2×2 intersectional rib optical waveguide switch with bow-tie electrode has been proposed and fabricated for the wavelength of 1.3-μm operation. The thickness of the SiGe layer is 2.6 μm and the width is 9 μm. The branch angle of the switch is 2° and the bow-tie angle is 1.5°. The on-state crosstalk is -19.6 dB, the off-state extinction ratio is 38.5 dB and the off-state insertion loss is less than 1.70 dB. The switching time is about 180 ns     

Fabrication and Evaluation of Nano-Scale Optical Circuits Using Sol-Gel Materials With Photo-Induced Refractive Index Variation Characteristics

Nano-scale optical circuits with core thickness of ~ 230 nm and core width of ~ 1 mum were fabricated and evaluated, using the photo-induced refractive index variation sol-gel materials, whose refractive index gradually increases by UV light exposure and baking. Propagation loss of linear waveguides was 1.86 dB/cm for TE mode and 1.89 dB/cm for TM mode at 633 nm in wavelength, indicating that there were small polarization dependences of ~ 0.03 dB/cm. Spot sizes of guided beams along core width direction and along core thickness direction were, respectively, 0.6 and 0.3 mu m for both TE mode and TM mode. Bending loss of S-bending waveguides was reduced from 0.44 to 0.24 dB for TE mode with increasing the bending curvature radius from 5 to 60 mu m. Although the bending loss for TM mode was slightly higher than that for TE mode, the difference was less than 10%. Branching loss of Y-branching waveguides was reduced from 1.33 to 0.08 dB for TE mode, and from 1.34 to 0.12 dB for TM mode with decreasing the branching angle from 80deg to 20deg. From these results, it is concluded that the photo-induced refractive index variation sol-gel materials can realize miniaturized optical circuits with sizes of several tens of microns and guided beam confinement within a cross section area less than 1.0 mum² with small polarization dependences, indicating potential applications to intra-chip optical interconnects.     

Broadband phase modulators in integrated fin-line technique for millimeter-wave applications

Three structures of broadband reflection type phase modulators in unilateral fin-line are presented. The circuits have been analysed assuming ideal transmission line equivalent circuits for the fin-line sections, while the switching element, a pin-diode, is represented by a typical equivalent circuit at Ka-band. The insertion loss in all three cases is better than 1.5 dB and the phase error for a 180 degrees phase shift is less than 4 degrees over a 12% bandwidth, while a 16% bandwidth is achieved for a 90 degrees modulator at a phase error of 2 degrees.     

Reflection-type optical waveguide switch with bow-tie electrode

Based on the total internal reflection and the plasma dispersion effect of SiGe alloy, an intersectional rib optical waveguide switch with bow-tie electrode has been proposed and fabricated for operating wavelengths of 1.3 and 1.55 μm. The thickness of the SiGe layer is 2.6 μm and the width is 9 μm. The branch angle of the switch is 2° and the bow-tie angle is 1.5°. The crosstalks are -19.6 dB for 1.3 μm and -21.8 dB for 1.55 μm. At both wavelengths, the extinction ratio is larger than 38.5 dB and the insertion loss is less than 1.70 dB. The switching time is about 180 ns     

太赫兹光子晶体光纤与天线设计

以聚甲基丙烯酸甲酯(PMMA)材料为基质,设计了一种空芯多孔包层结构的太赫兹光纤,中心的大孔缺陷用于传输太赫兹波,周围四层小孔可以将太赫兹波的传播限制在缺陷内部。利用COMSOL软件对光纤的损耗特性进行仿真分析发现,光纤在0.6 THz的泄露损耗低于0.1 dB/m,具有良好的传输特性。和金属波导口可以当作天线辐射电磁波的原理相似,光纤的端面也可以作为天线将内部传输的太赫兹波向外辐射,通过仿真分析,天线在0.59~0.61 THz的回波损耗低于-25 dB,方向性系数大于20 dB,半功率波束宽度约为13。     

基于耦合腔的太赫兹垂直传输结构

提出了一种工作在110 GHz的耦合腔垂直传输结构。在垂直金属腔的两端对称地装配两个模式变换单元,作为波导的两个激励端口。模式变换单元在50 μm厚度石英基片上实现,该基片采用通孔结构和双面镀金工艺。因此,该垂直传输结构在太赫兹频段具有较低的插入损耗。仿真结果与测试结果拟合良好,模式变换单元的 S₂₁仿真结果为?0.7 dB,测试结果小于?1.3 dB,在105~116 GHz带宽的反射系数低于?10 dB。     

20-Channel micro-optic grating demultiplexer for 1.1?1.6 ?m band using a small focusing parameter graded-index rod lens

A 20-channel micro-optic grating demultiplexer with a single-mode input fibre has been developed for 1.1?1.6 ?m band using a newly developed graded-index (Selfoc) rod lens with a small focusing parameter and an Si-etched reflection grating. Insertion losses were 1.9 to 3.5 dB. Isolation between adjacent channels was less than ?20 dB.     

New technique for the suppression of triple-transit signals in surface-acoustic-wave delay lines

An LiNbO3 surface-acoustic-wave delay line has been constructed which has an 8? dB single-transit loss and a triple-transit suppression (relative to the single transit) greater than 40 dB over a 25% bandwidth. The device uses a multistrip coupler to divert the unwanted acoustic reflection into an acoustic absorber. No extra production steps are required.     

一种新型光纤光栅无啁啾调谐方法

分析了基于弹性梁的光纤光栅调谐原理，引入了轴向直变传递系数的概念，提出利用部分纯弯曲调谐方法，可实现光纤光栅宽带无啁嗽调谐。在实验中，利用部分纯弯曲调谐法，获得了20．1nm的光纤光栅无啁嗽调谐范围，调谐线性拟合度为0．9996，调谐过程中光栅反射谱的3dB带宽变化小于0．07nm，峰值反射率变化小于0．2dB，基本无啁嗽现象产生，实验结果和理论分析一致。     

Non-blocking four-port optical router based on thermo- optic silicon microrings

By using silicon-on-insulator(SOI) platform, 12 channel waveguides, and four parallel-coupling one-microring resonator routing elements, a non-blocking four-port optical router is proposed. Structure design and optimization are performed on the routing elements at 1 550 nm. At drop state with a power consumption of 0 m W, the insertion loss of the drop port is less than 1.12 d B, and the crosstalk between the two output ports is less than-28 d B; at through state with a power consumption of 22 m W, the insertion loss of the through port is less than 0.45 d B, and the crosstalk between the two output ports is below-21 d B. Routing topology and function are demonstrated for the four-port optical router. The router can work at nine non-blocking routing states using the thermo-optic(TO) effect of silicon for tuning the resonance of each switching element. Detailed characterizations are presented, including output spectrum, insertion loss, and crosstalk. According to the analysis on all the data links of the router, the insertion loss is within the range of 0.13—3.36 d B, and the crosstalk is less than-19.46 d B. The router can meet the need of large-scale optical network-on-chip(ONo C).     

A novel couple-type power divider with large-angle low-losscharacteristics

A novel large-angle low-loss direction-coupler type power divider with designed ratio between output waveguides is proposed. The radiation loss is greatly reduced by using a micro-prism at the bend corner to compensate the phase mismatch due to bending. A normalized transmitted power of the power divider with a bend angle of 10° simulated by the semivectorial beam propagation method is about 93%, which is much larger than those were reported for single-mode waveguides. Application of more micro-prisms is also shown. The calculated loss of a symmetric large-angle 3-dB directional coupler with eight micro-prisms is less than 0.953 dB     

High-bandwidth, high-numerical aperture graded-index polymeroptical fiber

A new large core (0.5-1.0 mm) graded-index polymer optical fiber was proposed to solve the connection problem of the single-mode silica fiber indoor use for high speed multimedia network. The bending loss for 10-mm bending diameter was dramatically decreased from 20 dB to less than 1 dB by preparing the high numerical aperture graded-index polymer optical fiber. The bandwidth was 585.2 MHz km which was one hundred times larger than that of any existent step-index polymer optical fibers, and the attenuation was 150 dB/km at 650-nm wavelength     

New dual mode square waveguide-corner

The design principles and method for a wideband dual mode square waveguide 90 degrees corner are presented. Experimental results show that for 22% relative bandwidth, the reflection loss in either the E or H-plane (TE/sub 01/ and TE/sub 10/ modes) is better than -27.5 dB.<>