High-silica multimode channel waveguide structure for minimizing fiber-waveguide-fiber coupling loss

The optimum structure for high-silica channel waveguides which are connected to input and output graded-index fibers having a 50-μm core diameter and a 1.0-percent refractive-index difference is studied theoretically and experimentally. Theoretical optimum waveguide structure is obtained on the basis of ray optic analysis. For the step-index waveguide with 1.0-percent refractive-index difference, the theoretical minimum coupling loss (input coupling loss + output coupling loss) is 1.7 dB for an optimum core of 38 μm both in depth and width. For the graded-index waveguide with parabolic-index profile in the depth direction and step-index profile in the width direction, the theoretical coupling loss is 1.1 dB for an optimum core of 38 μm in width and 50 μm in depth. These estimations were in good agreement with the experimental results, which were 1.8 dB for the step-index waveguide and 1.3 dB for the graded-index waveguide.     

Harmonic and intermodulation performance of active integrated-optic waveguides

An empirical formula is developed for the static input/output optical characteristic of the active integrated-optic waveguide. Using this formula, closed-form analytical expressions, in terms of the ordinary Bessel functions, are obtained for the output optical components resulting from a modulated multisinusoidal optical input. Using these expressions the effect of the wavelength of the light input, the guide width, the modulation depth and the optical power for transperancy on the harmonic and intermodulation performance of the active integrated-optic waveguide can be studied.     

Monolithic waveguide zinc-oxide-on-silicon convolver

A monolithic waveguide zinc-oxide-on-silicon convolver has been constructed and operated at a centre frequency of 125 MHz. The zinc oxide is originally deposited over the whole substrate and then etched to form the waveguide. The waveguide width is 1/10 of the beam width at the input transducers, which should yield a 20 dB improvement in efficiency over a normal convolver with a beam width equal to the transducer width, after accounting for the loss in the input tapers. Such an improvement was observed in experimental devices.     

Surface wave scattering from a notch in a dielectric-covered groundplane: TE-mode analysis

026The problem of TE mode surface wave scattering from a rectangular notch in a dielectric-covered ground plane is considered. A Fourier-transform technique is used to express the scattered field in the spectral domain in terms of parallel-plate waveguide modes. The boundary conditions are enforced on the ground plane and the notch aperture to obtain simultaneous equations for the transmitted field inside the notch. The simultaneous equations are solved to obtain a solution in a fast convergent series, thus facilitating the numerical computation. The transmission, reflection, and scattering coefficients are found to oscillate as the notch width increases especially when the notch depth is comparable to and larger than one wavelength. A limited number of computations show that the reflected power loss is less than 2% when the notch width is less than one wavelength     

一种W波段一分八波导功分器的设计

提出了一种W波段波导八路功率分配器的结构。该功率分配器采用切角的E面T形结构来实现功率分配。通过调节切角深度、宽度及渐变波导最细处的尺寸,使输入阻抗匹配并实现等功率同相位的两路功分,最后采用级联的方式实现了W波段的八路波导功分。通过在输入输出端口处加入90°扭转波导,实现了输入输出端口的平面一致性;同时在结构中加入了135°扭转接头使结构更紧凑,节省了体积。运用HFSS仿真表明,该结构在88～90GHz范围内,S21～S91在-8.8～-9.4dB之间,S11小于-18.5dB,性能良好。     

Broadbanding of corrugated conical horns by means of the ring-loaded corrugated waveguide structure

Broadbanding of corrugated conical horns is investigated with the ring-loaded corrugated circular waveguide (RCWG) structure devised by the authors. The useful frequency bandwidth in which the corrugated horn is effective for the improvement of antenna properties is limited by the frequency characteristics of the horn-aperture field and input VSWR of the horn. By the precise analysis of the RCWG, the maximum frequency range in which the desirable field is obtained is much wider than that in the conventional corrugated circular waveguide, and is achieved almost independent of ring thickness, when ring width is about 20 percent of slot depth. The characteristic impedance of the RCWG is nearly equal to that of the homogeneous circular waveguide when ring thickness becomes large. Therefore, a good transformer between the RCWG and the homogeneous circular waveguide is achieved by increasing ring thickness from the RCWG toward the homogeneous waveguide. From the above investigations, it is found that in the ring-loaded corrugated horn, the useful bandwidth is 1.35 times broader than that in the conventional corrugated horn. The theoretical results are verified by the experimental results.     

Sub-THz Four-Way Waveguide Power Combiner With Low Insertion Loss

A four-way waveguide power divider has been developed in sub-THz band. The waveguide power divider was achieved with the improved H-plane T-junction structure. By tuning the depth and width at the junction of the waveguide, the input impendence was matched and the two-way output power amplitude and phase were at the same level. The four-way power divider was realized by the concatenation of two same T-junction at the two output ports. A sub-THz four-way passive power combiner is designed, fabricated and measured. The measure results show that the measured insertion loss of the fabricated four-way passive power combiner is less than 1.2 dB whereas the input return loss is greater than 14.8 dB from 97.5 to 101.7 GHz. Experiments on the sub-THz four-way passive power combiner show that a minimum insertion loss of 1 dB has been achieved at about 99.5 GHz. The measured minimum insertion loss of the waveguide power divider is half of the insertion loss for the entire passive power combiner (0.5 dB), which corresponds to a power-combining efficiency of 89 %. The measured results agree with the simulated ones closely.     

一种输入级模块复用的In-Zn-O薄膜晶体管行集成驱动电路

提出了一种新型的基于In-Zn-O薄膜晶体管(IZO TFT)的行集成驱动电路。该电路采用了输入级模块复用的驱动方法,即一级输入级驱动多级输出级,因此可以显著地减少输入级模块TFT的数量,缩减电路的面积,满足高分辨率显示屏设计,同时也可以迎合显示屏窄边框的审美需求。电路的输入级模块工作时间是输出级模块的n倍(n是一级输入级模块驱动输出级模块的级数),因此输入级尺寸可以做得更小。另外,该电路的驱动时钟频率是传统结构中一级输入级模块驱动一级输出级模块时钟频率的1/n,有效地降低了电路的动态耦合功耗。我们制作了20级的行集成驱动电路,一级输入级模块驱动两级输出级模块,该电路的尺寸为宽730μm,高为164μm,满足窄边框的要求。从实验测结果表明,该电路很好地满足300PPI的AMLCD或AMOLED显示屏的需求。     

Symmetric Reverse-Coupling Waveguide Orthomode Transducer for the 3-mm Band

We describe the design, construction, and performance of a waveguide orthomode transducer (OMT) for the 3-mm band (84-116 GHz). The OMT is based on a symmetric backward coupling structure and has a square waveguide input port (2.54 mm times 2.54 mm) and two single-mode waveguide outputs: a standard WR10 rectangular waveguide (2.54 mm times 1.27 mm), and an oval waveguide with full-radius corners. The reverse coupling structure is located in the common square waveguide arm and splits one polarization signal in two opposite rectangular waveguide sidearms using broadband -3-dB .E-plane branch-line hybrid couplers. The device was optimized using a commercial 3-D electromagnetic simulator. The OMT consists of two mechanical blocks fabricated in split- block configuration using conventional CNC milling machine. From 84 to 116 GHz, the measured input reflection coefficient was less than -17 dB, the cross polarization was less than -30 dB, the isolation between the outputs was greater than 50 dB, and the insertion loss was less than 0.35 dB at room temperature for both polarization channels. The device is suitable for scaling to higher frequency.     

Stress-Induced Birefringence Characteristics of Polymer Optical Rib Waveguides

We report the detailed numerical investigation of stress-induced material birefringence in polymer rib waveguide for the design of nonbirefringent waveguide devices. To accurately simulate the stress-induced effects we propose a more realistic model in the finite element analysis which considers the stresses induced over the entire sequential fabrication process. It is observed that the birefringence is nonuniform, and it is different for different etch depth and core width. The maximum birefringence in the core layer is observed near the lower cladding which decreases to zero toward the top surface. The influence of this material anisotropy on the modal birefringence is analyzed also for different rib structures. We found the stress effects on the modal birefringence to be largely affected by etch depth, while core width has small effect. It is also found that the deeply etched core has better birefringence stability. Finally, an accurate design of the zero-birefringence waveguide is illustrated by taking the stress effects into account, and the results are compared with experimental data. Excellent agreement between calculated and experimental results confirms the potential application of this work to aid in the design of polarization-insensitive waveguide devices.     

The field radiated by a single-mode optical waveguide excited by a field with a complex amplitude-phase spatial distribution

A single-mode optical waveguide excited by a field having a complex amplitude??phase spatial distribution is considered. The field formed at the output of the waveguide is investigated. It is shown that the field structure at the input of the waveguide is transformed at its output into a simple structure with a distribution close to the Gaussian one. It is found that higher order spatial maxima of the input field falling within the waveguide??s aperture also participate in the formation of the output field.     

Two-mode interference photonic waveguide switch

Based on the two-mode interference principle and the free-carrier plasma dispersion effect, a two-mode interference (TMI) photonic waveguide switch with double carrier injection has been designed and fabricated for application in fiber-optic communications. It consists of an input Y-branch with single-mode ridge waveguides, a TMI waveguide coupling section, and an output Y-branch with single-mode ridge waveguides. The single-mode waveguides and the two-mode waveguide are composed of a SiGe waveguide layer on a Si substrate. The width of the TMI region of the switch is two times that of the single-mode waveguide. On the top of the TMI region and one side of the TMI region, two abrupt p-n junctions are made to inject the carriers into the optical modulation region; on the other side of the TMI region, an abrupt carrier collection region is made to collect the carriers when they are forward biased, so that the double carrier injection photonic waveguide switch has the lowest injection current density. The waveguide layers are made of SiGe/Si material, and the rib waveguides are realized by reactive ion etching. The carrier injection regions and the carrier collection region are formed by ion implantation. The input and output facets of the waveguides were ground and polished by a mechanical method. The switch was characterized by using a 1310-nm InGaAsP/InP heterostructure laser diode. Its insertion loss and ON-state crosstalk were measured to be 2.74 and -15.5 dB, respectively, at a total switching current of 110 mA. The switching time is 180 ns, and the fastest switching time is up to 30 ns.     

6061铝水导激光加工工艺参数优化研究

为研究水导激光加工关键工艺参数对6061铝切槽形状与组织性能的影响,利用自研的水导激光加工设备,对6061铝开展了包括激光功率、激光重复频率、进给速度及加工次数在内的多个关键工艺参数的多因素影响切槽实验.利用金相显微镜对加工沟槽的深宽比、侧壁锥度及组织变化情况进行了测量与分析.实验结果表明:激光重复频率对沟槽宽度有较明...     

The Paradoxical Surface Wave (Crack Wave) in Ferrite-Filled Waveguides

Existing theories that relate to propagation in a rectangular waveguide loaded with a transversely magnetized slab of ferrite are reviewed and new points brought out. In the loss-free case, in which the ferrite stab lies against one of the waveguide walls, conflicting results are obtained. If the width of the air gap between the ferrite slab and the waveguide wall is set equal to zero, a single surface wave propagating in one direction only is predicted. This result leads to a thermodynamic paradox. If, however, the air gap is assumed infinitely small but different from zero, two surface wave modes, which transport energy in opposite directions, are predicted. The aim of this paper is to establish whether or not a surface wave exists when there is no air gap for a real structure which is not free of loss. The experimental results show conclusively that the surface wave is present. It is concluded that a mathematical model is required, which assumes losses. If for reasons of simplicity a lossless model is used, then it must be assumed that the width of the air gap is never identical to zero. The structure selected for the experimental work consisted of a rectangular block of ferrite that completely filled the cross section of an X-band waveguide.     

硅基狭缝脊形波导的几何尺寸对光场分布的影响

文中采用时域有限差分模拟的方法,研究了狭缝脊形波导中狭缝的宽度、狭缝两侧波导的宽度以及狭缝的深度对狭缝脊形波导光场分布的影响。在狭缝脊型波导中, 随着狭缝宽度的增加, 其归一化光功率先增大后减小;同样,光功率随着狭缝两侧波导的增加也呈现出先增加后减小的现象;随着狭缝刻蚀深度的增加,归一化光功率是逐渐增大的。通过比较狭缝中归一化光功率的值,将其影响量化,进一步找到最合适狭缝脊形波导的几何尺寸。实验结果表明,当狭缝的宽度为40 nm,两侧波导的宽度为220 nm,狭缝刻蚀深度为220 nm时,归一化光功率达到最大值为13.54 %。该仿真结果有助于优化狭缝脊形波导与调制器制造和集成。     

MMI型1.31/1.55 μm GaAs波分复用/解复用器的研制

利用多模波导的自镜像原理,分析设计了一种能直接与单模光纤相耦合的具有最小循环比的1.31/1.55 μm波长的GaAs/GaAlAs波分复用/解复用器。该器件的输入、输出单模波导和SIE多模波导采用离散谱折射率法进行优化设计,最后获得了当输入、输出单模波导宽为3 μm、SIE多模波导宽度和最佳耦合长度分别为18 μm和5 602.8 μm时,该器件对1.31 μm和1.55 μm两个波长的隔离度均在70 dB以上,且传输损耗小于0.1 dB。     

GaInP/AlGaInP脊形波导激光器器件结构的优化研究

通过优化脊形波导的结构参数可以降低脊形波导激光器的阈值电流,提出了实现亚微米脊宽,从而降低阈值电流的方法。针对脊形波导制作过程中蚀刻深度不易控制的问题,对GaInP/AlGaInP材料中加入蚀刻阻挡层进行了研究。     

Single-mode and polarization-independent silicon-on-insulator waveguides with small cross section

The fabrication restrictions that must be imposed on the geometry of optical waveguides to make them behave as single-mode devices are well known for relatively large waveguides, with shallow etch depth. However, the restrictions for small waveguides (/spl sim/1 /spl mu/m or less in cross section) are not well understood. Furthermore, it is usually a requirement that these waveguides are polarization independent, which further complicates the issues. This paper reports on the simulations of the conditions for both single-mode behavior and polarization independence, for small and deeply etched silicon-on-insulator (SOI) waveguides. The aim is to satisfy both conditions simultaneously. The results show that at larger waveguide widths, waveguide etch depth has little effect on the mode birefringence because the transverse-electric (TE) mode (horizontal-polarized mode) is well confined under the rib region. However, at smaller rib widths, the etch depth has a large influence on birefringence. An approximate equation relating the rib-waveguide width and etch depth to obtain polarization-independent operation is derived. It is possible to achieve single-mode operation at both polarizations while maintaining polarization independence for each of the waveguide heights used in this paper but may be difficult for other dimensions. For example, a 1-/spl mu/m SOI rib waveguide with an etch depth of 0.64 /spl mu/m and rib width of 0.52 /spl mu/m is predicted to exhibit such characteristics.     

非对称结构阵列波导光栅解复用器的传输效率

基于光波导模场分布的高斯函数近似表达式,给出非对称结构阵列波导光栅解复用器信号通道对其中心波长光谱响应度的函数表达式,分析了光谱响应度与器件基本参数的关系.基于实际通道信号光谱分布的高斯函数近似表达,给出非对称结构阵列波导光栅解复用器信号通道对实际输入信号的传输效率,分析了输入信号光谱宽度对器件通道实际传输效率的影响.     

硅基二氧化硅波导的双折射效应补偿理论分析

使用有限元方法分析了硅基二氧化硅波导的两种偏振补偿方法的可行性.结果表明采用应力释放槽和调节上包层热膨胀系数都可改善波导的偏振相关性.采用应力释放槽可以释放波导中的由于硅衬底与二氧化硅热膨胀系数失配造成的压应力,可以影响芯区附近的应力分布,但是只有释放槽的深度达到一定值时才能改善波导的偏振相关性,增大槽的宽度也在一定程度改善偏振相关性,但效果较差.调节波导上包层的热膨胀系数可以很好的解决波导的偏振相关问题,而调节波导的其它层的热膨胀系数对波导的偏振相关作用较小.