宽带太赫兹非对称十字孔矩形波导定向耦合器的设计

根据波导定向耦合器原理,设计了一种太赫兹频段,采用非对称十字形孔耦合的矩形波导定向耦合器。通过优化波导结构和十字形耦合孔参数,在WR4波导频段内,实现了稳定的耦合平坦度、良好的方向性和工作带宽。仿真结果表明该型波导定向耦合器耦合度稳定在-19.9d B~-22.0d B之间,方向性优于32d B,相对工作带宽为40%。     

1.3GHz高功率输入耦合器样机设计北大核心CSCD

本文研究的课题是1.3 GHz高功率输入耦合器模拟仿真,是基于2018年启动的上海光源硬X射线自由电子激光器大科学装置项目。该项目采用9-cell超导腔加速粒子,在每个超导腔和功率源之间连接一个输入耦合器,负责将功率源的能量传输到超导腔中加速粒子。本文设计是基于同轴线结构的高功率输入耦合器,其结构大致可分为四个部件:冷端、热端、同轴转换波导和内导体调节驱动。其中冷端和热端各包含一个圆柱形陶瓷窗,分别称为冷窗和热窗。冷端外导体和热端内外导体采用波纹管结构设计,通过内导体调节驱动调节耦合杆可以控制波纹管的伸缩,以改变内导体天线插入腔体的深度,从而实现耦合度可调以匹配不同的束流负载。同轴转换波导通过实现矩形波导到同轴波导的过渡,从而实现TE10模到TEM模的模式变换。本文就高功率耦合器的RF仿真方面阐述耦合器的设计过程。     

1.3GHz高功率输入耦合器样机设计

本文研究的课题是1.3 GHz高功率输入耦合器模拟仿真,是基于2018年启动的上海光源硬X射线自由电子激光器大科学装置项目。该项目采用9-cell超导腔加速粒子,在每个超导腔和功率源之间连接一个输入耦合器,负责将功率源的能量传输到超导腔中加速粒子。本文设计是基于同轴线结构的高功率输入耦合器,其结构大致可分为四个部件:冷端、热端、同轴转换波导和内导体调节驱动。其中冷端和热端各包含一个圆柱形陶瓷窗,分别称为冷窗和热窗。冷端外导体和热端内外导体采用波纹管结构设计,通过内导体调节驱动调节耦合杆可以控制波纹管的伸缩,以改变内导体天线插入腔体的深度,从而实现耦合度可调以匹配不同的束流负载。同轴转换波导通过实现矩形波导到同轴波导的过渡,从而实现TE_(10)模到TEM模的模式变换。本文就高功率耦合器的RF仿真方面阐述耦合器的设计过程。     

一种新颖的偏振不敏感的阵列波导光栅

提出了一种新颖偏振不敏感的阵列波导光栅(AWG)。器件的输入端增加了一个全光学偏振自动控制器(AOPSC),可将注入AWG的随机偏振的输入光转换为与AWG中TE0模偏振方向相同且功率损耗很小的线偏振光。AWG结构设计采用非对称的平面波导,包层与波导芯层的相对折射率差为0.7%,波导芯层的宽厚比要高,可以消除TE与TM模的简并,使波导中只能激励TE0模,而使TM0模截止。这种AWG结构完全消除了不同偏振态信号光对AWG工作性能的影响,从而使器件对偏振不敏感。设计的8×0.8nm器件整体尺寸为2cm×1cm,串扰优于-30dB,最大插入损耗为4.2dB。     

利用三个3×3耦合器串连构成干涉型三波长波分复用器

针对三通道波分复用技术,本文提出了一种利用三个3×3光纤耦合器级联细成的全光纤Mach-Zehnder干涉仪型三波分复用器,运用光纤传输理论和矩阵理论,得到光谱的输出表迭式.通过数值模拟分析了各3×3耦合器耦合比和光纤臂长差对该三波分复用器的影响,并进行了实验.结果表明,当组成的全光纤 Mach-Zehnder干涉仪型三波分复用器的三条光纤干涉臂两两之间分别存在长度差△L和2△L时,在耦合器分光比取一些定值时即可实现三波分复用功能,三端口输出谱线理想,波长间隔仅仅取决于△L的大小,且该器件的输出谱线对耦合器的耦合比不太敏感.实验样品采用的波段为1.55μm,波长复用间隔为0.8 nm,实验所得的结果与理论相吻合.     

非对称光纤反射镜的可调谐光纤激光器

提出一种非对称窄带光纤环形反射镜结构的可调谐掺铒光纤激光器。980nm泵浦光对掺铒有源光纤进行抽运,高双折射光纤、偏振控制器（PC）和光纤耦合器构成窄带光纤反射镜,窄带光纤反射镜和普通光纤反射镜组成激光谐振腔,利用窄带光纤反射镜工作带宽纳米量级的特性得到单纵模激光。调整偏振控制器改变反射镜对不同波长的反射率,实现可变波长的激光输出。实验表明,该激光器的工作带宽为8nm,120mW泵浦光条件下最大输出功率为4mW,3dB带宽（脉冲的半高宽度）小于0．2nm,边模抑制比为20dB以上,在1527nm～1535nm的波长范围内观察到稳定激光输出。     

全息光聚合法制备聚合物波导光栅耦合器

在光通信及集成光学中,光波耦合器是关键器件之一。本文中选择树脂CN960E60单体作为聚合体系,采用自由基型对532nm波长敏感的单光子引发剂,利用全息光聚合法制备出聚合物波导光栅耦合器。在进行聚合实验之前,首先测定了聚合材料的透射光谱。实验观测结果证实了用光全息聚合方法制作波导光栅耦合器的可行性。     

Ka波段TE01模回旋行波管宽带输入耦合器的设计

Ka波段TE01模回旋行波管的输入耦合器将矩形波导中输入的TE10模转化为圆波导中TE01模的行波场,以实现对回旋电子注角向速度的调制。本文首先对Ka波段TE01模回旋行波管的输入耦合器进行了解析分析和数值计算。通过数值计算得到输入耦合器的初步结构和尺寸,然后利用三维高频分析软件HFSS进行精确的模拟和修正。通过优化设计在Ka波段获得了3 dB带宽约为3 GHz,1 dB带宽大于2GHz的高性能TE1□0-TE4◎11-TE0○1输入耦合器和3 dB带宽约为3.5 GHz,1 dB带宽约为3 GHz的高性能TE1□0-TE5◎11-TE0○1输入耦合器。冷测实验研究表明优化设计结果与冷测结果相吻合。     

一种新型全光纤弹速测量系统的研制

研制了一种新型的利用激光光束反射原理的全光纤弹速测量系统。该系统采用了全光纤结构和光纤耦合器等无源器件,以输出光功率1mW, 工作波长1300nm的半导体激光器作为测试系统的光源,用光纤耦合器进行分光,实现了在一根光纤中同时传输光源和接受目标反射的信号光,避免了复杂的调节和准直过程。该系统结构简单、可靠性高,利用它,成功地测量了霍普金森杆发射的子弹速度,结果表明其速度测量相对不确定度小于1%。     

纳米多孔光波导漏模共振传感器的折射率灵敏度分析(英文)

在玻璃基片上射频溅射50 nm厚的金膜,然后利用TiO2胶体溶液在金膜表面制备了厚度约为320 nm的TiO2纳米多孔薄膜.以此双层膜为漏模光波导芯片,构建了基于Kretschmann结构的波长调制型光波导漏模共振(LMR)传感器.利用扫描电子显微镜(SEM)观测了TiO2纳米多孔薄膜的表面和横截面形貌.实验研究了在纳米多孔光波导中给定漏模的共振波长及折射率灵敏度与入射角的依赖关系.结果表明,随着入射角的增大,共振波长逐渐蓝移,折射率灵敏度随之下降.此外,与传统的表面等离子体共振(SPR)传感器进行了对比,结果表明在相同的共振波长下,纳米多孔光波导LMR传感器折射率灵敏度大于SPR传感器.     

Holographic Bragg grating input-output couplers for polymer waveguides at an 850-nm wavelength

Bragg gratings used as input-output couplers in polymeric waveguides have been demonstrated at infrared wavelengths. These Bragg grating couplers were holographically formed volume phase gratings with a near-45 degrees fringe slant angle embedded directly into a waveguide layer. A photopolymer was used for both producing a planar waveguide and constructing the embedded Bragg grating coupler. A coupling efficiency of 23% for input and 5% for output has been achieved at 850 nm. The output-coupling beam profiles are also discussed.     

Integration of photonic and silver nanowire plasmonic waveguides

Future optical data transmission modules will require the integration of more than 10,000 x 10,000 input and output channels to increase data transmission rates and capacity. This level of integration, which greatly exceeds that of a conventional diffraction-limited photonic integrated circuit, will require the use of waveguides with a mode confinement below the diffraction limit, and also the integration of these waveguides with diffraction-limited components. We propose to integrate multiple silver nanowire plasmonic waveguides with polymer optical waveguides for the nanoscale confinement and guiding of light on a chip. In our device, the nanowires lay perpendicular to the polymer waveguide with one end inside the polymer. We theoretically predict and experimentally demonstrate coupling of light into multiple nanowires from the same waveguide, and also demonstrate control over the degree of coupling by changing the light polarization.     

Fabrication and characterization of a third-order nonlinear organic-polymer composite glass waveguide: a self-phase modulator

Composite organic-polymer glass optical waveguides in which coupling to the nonlinear organic-polymer layers was achieved by excitement of the underlying ion-exchanged glass waveguide and coupling of the light to the organic-polymer layer were fabricated and measured. A picosecond pulsed color center laser (λ = 1.5 μm) was used to measure the third-order optical susceptibility χ((3))(-w; w, -w, w) in an organic-dye-polymer composite glass waveguide with a Mach-Zehnder interferometer. For a squaryliumdye-doped poly(methyl methacrylate)-styrene-acrylonitrile matrix polymer layer, a composite χ((3)) of roughly 90, in units of (χLiNbO)(3)((3)), was measured.     

Polarization dependence of the coupling ratio in LiTaO3 directional couplers

The effect of design and fabrication parameters on the polarization dependence of the splitting ratio in directional couplers produced in LiTaO3 by Zn diffusion has been investigated experimentally at a wavelength of 1558 nm. The directional couplers featured various combinations of waveguide width, separation gaps between waveguides, bending angle, and diffusion conditions. In each case the coupling region was 3.5 mm long. Of particular interest was the identification of parameter sets for which the sum of power splitting ratios from TE and TM inputs equals unity at the output, as needed for electro-optic tunable filters with relaxed beam-splitter requirements.     

玻璃基掩埋式光波导堆栈的制作与表征

在硅酸盐光学玻璃基片上制作了光波导堆栈, 这种光波导堆栈通过Ag⁺/Na⁺熔盐离子交换和电场辅助离子扩散技术顺次制作了两层掩埋式光波导. 对光波导堆栈的横截面显微结构进行了观察, 并对堆栈中两层波导的损耗特性进行了测试. 所获得的光波导堆栈中的上、下两层波导芯部分别位于玻璃表面以下14和35 μm处; 上层光波导芯部尺寸约为12 μm×7 μm; 下层光波导芯部尺寸约为9 μm×8 μm. 通光测试显示两层波导在1.55 μm工作波长下均为单模光波导, 且两者之间没有相互耦合. 损耗测试分析结果显示: 堆栈中两层光波导的传输损耗均约为0.12 dB/cm,与单模光纤之间的耦合损耗分别为0.78和0.73 dB. 分析表明, 这种光波导堆栈在玻璃基集成光芯片的高密度集成方面具有很好的应用前景.     

THz wavefront manipulation based on metal waveguides

In this paper, two waveguiding structures for arbitrary wavefront manipulation in the terahertz spectral region were proposed, designed and characterized. The first structure consists of parallel stack copper plates forming an array of parallel-plate waveguides (PPWGs). The second structure is three-dimensional metal rectangular waveguides array. The phase delay of the input wave after passing through the waveguide array is mainly determined by the effective index of the waveguides. Therefore, the waveguide array can be engineered using different core width distribution to generate any desired light beam. Examples, working at the frequency of 0.3 THz show that good focusing phenomenon with different focus lengths and spot sizes were observed, as well as arbitrarily tilted propagation of incident plane waves. The structure introduces a new method to perform wavefront manipulation, and can be utilized in many important applications in terahertz imaging and communication systems.     

Two-dimensional array self-assembled quantum dot sub-diffraction waveguides with low loss and low crosstalk

We model and demonstrate the behavior of two-dimensional (2D) self-assembled quantum dot (QD) sub-diffraction waveguides. By pumping the gain-enabled semiconductor nanoparticles and introducing a signal light, energy coupling of stimulated photons from the QDs enables light transmission along the waveguide. Monte Carlo simulation with randomized inter-dot separation reveals that the optical gain necessary for unity transfer is 3.1 × 10(7)?m(-1) for a 2D (2?μm length by 500?nm width) array compared to 11.6 × 10(7)?m(-1) for a 1D (2?μm length) given 8?nm diameter quantum dots. The theoretical results are borne out in experiments on 2D arrays by measurement of negligible crosstalk component with as little as 200?nm waveguide separation and is indicative of near-field optical coupling behavior. The transmission loss for 500?nm wide structures is determined to be close to 3?dB/4?μm, whereas that for 100?nm width is 3?dB/2.3?μm. Accordingly, higher pump power and gain would be necessary on the narrower device to create similar throughput. Considering existing nanoscale propagation methods, which commonly use negative dielectric materials, our waveguide shows an improved loss characteristic with comparable or smaller dimensions. Thus, the application of QDs to nanophotonic waveguiding represents a promising path towards ultra-high density photonic integrated circuits.     

Empirical model for the waveguiding properties of directly UV-written waveguides

We present an empirical model for the waveguiding properties of directly UV-written planar waveguides in silica-on-silicon. The waveguides are described by a rectangular core step-index profile, in which model parameters are found by comparison of the measured waveguide width and effective index with modal field calculations. The model is used as input for beam propagation method calculations to design UV-written optical components. Subsequent fabrication of such components showed a good agreement with the model predictions. Using the model will reduce the number of iterations and thereby the development time of new optical devices.     

Characterization of a compact silicon-based slot-to-strip waveguide crossing

A compact crossing scheme for a silicon-based slot-to-strip (or vice versa) waveguide is proposed and analyzed by using a finite-difference time-domain method, where a strip–multimode waveguide (SMW) crossing is used at the center and two logarithmically tapered slot-to-strip mode converters are incorporated into the ports with slot waveguides. For the input ports with slot waveguides and output ports with strip waveguides, the guided modes are efficiently transformed through the mode converter, and then enter into the SMW, where the fields converge at the center of the intersection due to the self-imaging effect. Hence, the size of the input beam is much smaller than the width of the SMW at the crossing center, leading to significant reductions of both crosstalk and radiation loss. The numerical results show that a slot-to-strip waveguide crossing operating at a wavelength of 1.55?μm can be achieved with insertion loss, crosstalk, and reflection of 0.134/0.182, ?36.18/?38.6, and ?35.8/?42.02?dB for input ports with slot/strip waveguides, respectively.     

Characteristic analysis of nanosilicon rectangular waveguides for planar light-wave circuits of high integration

When a full-vectorial finite-difference method is used, rectangular Si waveguides can be characterized for planar light-wave circuits of high integration. The single-mode condition for a rectangular Si waveguide is obtained first. The birefringence, which can be adjusted by modifying the thickness of the cladding layer, is also studied. For a nano-Si rectangular waveguide the pure bending loss is very small even for an ultrasmall bending radius (e.g., a few micrometers), and the transition loss becomes dominant. The width and height are optimized to minimize the bending radius for the requirement that the bending loss is smaller than 0.1 dB. Finally the coupling between two parallel straight waveguides is analyzed, and it is shown that there is an optimal width for the maximal coupling length.