棱镜-漏波导耦合器的理论分析

根据多光束干涉原理,理论上分析了棱镜-漏波导耦合器,且与棱镜-波导耦合器作了比较,给出正确使用这两种耦合器的判据.分析结果表明,在强耦合条件下,棱镜-漏波导耦合器可用于薄膜参数测量和光波导输入-输出耦合;对于弱耦合,本文的结果与Tien和Ulrich的理论一致.     

Optimal design of coupling waveguide structure for adiabatic optical directional full couplers weighted by sin-square and raised-cosine functions

The optimal design of coupling waveguide structure for adiabatic optical directional full couplers (AODFC) based on weighted sin-square function (SSF) and raised-cosine function (RCF) are investigated in this paper. The coupling lengths with a crosstalk smaller than −30 dB at the operating wavelength of 1.57 μm resulted in a value of 3.0 and 2.4 mm for the SSF and RCF cases, respectively. Under the same level of crosstalk, the wavelength ranges obtained by weighted SSF and RCF could be varied about 1.33-1.70 μm and 1.27-1.70 μm with coupler lengths of 6.0 and 5.5 mm, respectively. Clearly, the AODFC weighted by RCF has the superior performances of both short coupling length and broad wavelength ranges.     

Research on mechanism for high light absorption of micro-structured silicon

The mechanism of the high light absorption of surface-microstructure silicon is discussed using optical simulation based on Monte Carlo method in this article. Calculation results indicate that the micro-structured surface and high refractive index of material are the two key factors that effectively reduce the reflection, especially transmittance, of the material instead of surface wave and sulfur. In addition, this shows clearly a development in direction for manufacturing new type detectors and increasing the efficiency of traditional detector effectively in the future.     

THz波段渐变波导中的多模传输特性

 根据耦合波理论,推导出轴对称渐变波导中, 考虑波导壁损耗时的多模传输时域耦合波方程组,并给出该方程组中各模式间耦合系数的具体表达式。据此编写了渐变波导中多模传输特性数值模拟程序。利用该程序计算了在THz波段圆波导中的模式衰减,在THz波段研究波导中的多模传输特性时,必须考虑波导壁的阻抗损耗影响。数值分析了直波导中的模式耦合问题,从而证实了波导壁有限电导率能产生模式耦合这一耦合机制。介绍了利用该程序数值分析波导耦合器和过渡器中多模传输特性的两个例子,利用该程序可对波导耦合器和过渡器中的多模传输特性进行数值模拟分析,进而对结构进行设计和优化。     

THz波段渐变波导中的多模传输特性

根据耦合波理论,推导出轴对称渐变波导中, 考虑波导壁损耗时的多模传输时域耦合波方程组,并给出该方程组中各模式间耦合系数的具体表达式。据此编写了渐变波导中多模传输特性数值模拟程序。利用该程序计算了在THz波段圆波导中的模式衰减,在THz波段研究波导中的多模传输特性时,必须考虑波导壁的阻抗损耗影响。数值分析了直波导中的模式耦合问题,从而证实了波导壁有限电导率能产生模式耦合这一耦合机制。介绍了利用该程序数值分析波导耦合器和过渡器中多模传输特性的两个例子,利用该程序可对波导耦合器和过渡器中的多模传输特性进行数值模拟分析,进而对结构进行设计和优化。     

Second harmonic generation by femtosecond Yb-doped fiber laser source based on PPKTP waveguide fabricated by femtosecond laser direct writing

The frequency doubling of femtosecond pulses from an Yb-doped fiber laser source was demonstrated in a PPKTP waveguide fabricated by femtosecond laser direct writing. The PPKTP waveguide contains a fixed period of 8.9 μm and the feomtosecond fundamental pulses have a central wavelength of 1044 nm. A maximum SHG power of 406 mW was produced, yielding a conversion efficiency of 5.6%. Numerical simulations were carried out to investigate the property of frequency doubling for femtosecond pulses. The results show that the SHG process proceeds even the quasi-phase-matching (QPM) condition is not well satisfied, which is significantly different from that of “long” pulses or CW light and is accorded with the experimental results.     

统一非对称光波导横向耦合模理论分析

光波导横向耦合模理论包含正交耦合模理论和非正交耦合模理论两大类, 为了追求形式上的完美, 两类理论没有统一的解析解, 并且都没有对非匹配耦合系统中耦合功率的非对称性进行深入研究. 本文一方面由Helmholtz方程出发推导出了一种新型的非正交耦合模方程, 并对两类理论中的耦合模方程进行了统一处理和求解, 得到了一种统一的解析解; 另一方面根据所得到的统一的解析解对非匹配耦合系统中耦合功率的非对称性进行了详细研究, 计算结果表明非匹配耦合系统中的最大互耦合功率和最小自耦合功率均可用统一的解析解进行近似计算. 关键词： 光波导 耦合模理论 耦合器 最大耦合功率     

一种硅基SiO2波导耦合器的设计与分析

波导耦合器是组成光纤传感系统和光纤通信系统光收发组件及模块的重要元器件,是实现光收发模块一体化光电集成的基础。给出了一种用光纤陀螺系统的X型四端口波导耦合器的工作原理,采用有效折射率法和BPM(Beam propagation method)法建立了耦合器的数学模型,计算并分析了耦合器尺寸在尽可能小的情况下和在满足单模传输的条件下耦合器的耦合系数、有效耦合长度、分光比以及回波损耗等参数之间的关系,并对其关键技术进行了系统的研究。仿真结果表明,所设计的波导耦合器在低损耗情况下分光比可达到50%∶50%,耦合器全长为33.5mm,输入输出波导间距为410μm,芯层截面积为6μm×6μm。     

基于介孔TiO_2薄膜等离子体波导的拉曼光谱技术研究

利用溶胶-凝胶分子模板法在表面覆金的玻璃基底上制备275 nm厚的介孔二氧化钛(TiO_2)薄膜,形成等离子体波导(PW)传感芯片.利用菲涅耳公式拟合实验测得的导模共振波长,得出TiO_2薄膜的多孔度约为0.589.基于光学互易定理仿真分析了置于介孔导波层中的电偶极子的拉曼辐射角分布,结果表明:辐射到衬底中的拉曼光包含沿导模共振角辐射的定向信号和辐射角小于全反射角的非定向信号;前者需借助棱镜耦合器才能被探测到,后者可从芯片背面直接被探测到;从导波层直接辐射到空气中的拉曼光称为背向信号,它的角分布呈发散式,几乎不受棱镜耦合器影响;定向信号的最大功率值远大于非定向信号和背向信号的相应值.实验研究了吸附于介孔导波层中的结晶紫分子的拉曼光谱,采用体光束激发方式探测到了定向、非定向和背向拉曼信号,定向信号强度的最大值是非定向信号的2倍多,在使用棱镜耦合器前后测得的背向信号强度几乎不变.     

二维平板光子晶体直波导的制备和光传输特性的测量

利用聚焦离子束刻蚀的方法在SOI(silicon on insulator)基片上制备了W3型二维光子晶体直波导.观察并测量了近红外激光通过光子晶体波导的散射图形和透过谱.实验结果说明，激光在有引入引出脊形波导的光子晶体直波导中具有很好的传输特性. 关键词： 光子晶体波导 光子带隙 脊型波导     

T-shaped dielectric slot waveguides for efficient control of birefringence and polarization independent directional coupling

A novel dielectric slot waveguide supporting strongly confined field in a T-shaped low-index slot region for both TE and TM polarizations is proposed and analyzed. Numerical simulations have demonstrated that quite different birefringent modal properties are achievable with tight optical confinement in the slot by tuning key geometrical parameters of the waveguide. Based on such a slot structure, the characteristics of directional couplers are investigated and the conditions for polarization independent coupling are also given. The presented T-shaped slot waveguide might be employed in integrated photonic systems as important building blocks enabling a number of potential applications.     

一种电光可调的铌酸锂/钠基表面等离子体定向耦合器

为了满足日益增加的集成光子器件设计的需求,本文研究了一种铌酸锂/钠表面等离子体波导(Li Nb O3/Na surface plasmonic waveguide, LNSPW),并利用LNSPW构成电光可调的定向耦合器(directional coupling,DC).利用有限元方法 (finite element method, FEM)对波导的模式特性和耦合器的耦合特性进行了分析.结果表明,随着波导尺寸的增大,传播长度可达约200μm,归一化有效模场面积小于0.4.通过调节耦合间距(W_gap)、耦合长度(L_C)和工作波长(λ)等参数,铌酸锂钠表面等离子体波导构建的定向耦合结构可实现3 d B耦合.当W_gap=100 nm和L_C=17μm时, DC在V₀=53 V时可实现3 d B耦合,且具有较好的方向性和隔离度.LNSPW的研究为实现可调的DC提供了一种可行的方案,在集成电光可调器件研究领域有潜在的应用前景.除此之外, LNSPW还可广泛应用于非线性光学、光信号处理及光全...     

A wide-band polymeric electro-optic modulator array based on unidirectional coupling between multi-mode waveguide array and a vertical configured dumping planar waveguide

A polymeric wide-band electro-optic (EO) modulator array based on unidirectional mode-coupling between the guiding multi-mode waveguide array and a vertical configured planar dumping waveguide was developed. A low insertion loss of <1.7 dB was obtained due to asymmetrically designed guiding waveguide and the dumping waveguide. A modulation depth of 91% was achieved with the device length of 3.5 cm at a low driving voltage of 3.2 V. The employment of the dumping planar waveguide not only provides an efficient way to achieve the unidirectional coupling mechanism, but also effectively confines the light coupled from the guiding waveguides within the planar dumping waveguide. The combination of unidirectional coupling and light confinement effects ensures low cross talk of <22 dB between adjacent guiding waveguides. Since the proposed modulator is based on the unidirectional coupling mechanism, it is intrinsically wide-band. A wide-band operation from 1308 to 1324 nm was experimentally obtained. The unidirectional mode-coupling-based wide-band modulation principle can be readily applied to other wavelengths, such as 1330 and 1550 nm ranges.     

测量单模波导参数的新方法:导模和漏模的双偏振测量

本文提出测量单模波导参数的新方法.用棱镜耦合器测量两种偏振基导模和基漏模的模折射率,并由相应的四个模方程确定单模波导参数.其测量精度优于纯导模测量.用这种方法测量了单模玻璃波导参数,并对误差来源作了理论分析.     

Design and fabrication of a three-dimensional polymer optical waveguide polarization splitter

We present a design and fabrication of a three-dimensional polymer optical waveguide polarization splitter by taking into consideration of the induced birefringence effect of the polymer. We show that it is not possible to couple TM light from one waveguide to the other but evanescent coupling for TE light is possible. Hence the polarization splitter can be designed by considering TE mode coupling alone. This has an advantage of short interaction length of the device. Based on this consideration, we fabricated a polarization splitter with a TE extinction ratio of 15 dB and TM extinction ratio of 21 dB.     

Design of short length and C+L-band mismatched optical coupler with waveguide weighted by the Blackman function

A mismatched optical coupler with waveguide weighted by the Blackman function is numerically investigated in the demand of short length, C+L-band, and low crosstalk. Utilizing the full factorial design, the structure parameters of coupling waveguide are obtained by beam propagation method. In the condition of crosstalk of −35 dB, the mismatched optical coupler with proper selected waveguide structure parameters is found to have a coupling length of 3.60 mm in the transmission wavelength ranges of C+L-band (1.53-1.61 μm). Obviously, the selection and design of waveguide structure are very important to satisfy the qualities of a mismatched optical coupler for the demand of short length, broad bandwidth, and low crosstalk.     

Slow light performance enhancement of graphene-based photonic crystal waveguide

We propose a graphene-based photonic crystal (PC) slow light waveguide, which is realized by creating periodical air holes in a silicon layer to achieve spatially varying chemical potentials of graphene. The structure is optimized around 30 THz, and a large group index of 166.6 is obtained, with a very low propagation loss of ?2.1 dB/um. The corresponding normalized delay-bandwidth product reaches as high as 4.00. Furthermore, the slow light performance can be dynamically tuned by changing a bias voltage. The center frequency of the slow light waveguide can be tuned between 19.1 THz and 27.4 THz. Our results suggest that graphene-based PC structures are very promising for slow light devices.     

二维三角晶格光子晶体波导的出射光集束传播

为了解决光子晶体波导出射端光场控制, 同时解决二维三角晶格光子晶体波导出射光辐射困难的问题。利用二维三角晶格光子晶体设计了一种新型光子晶体波导出射口结构。在二维三角晶格光子晶体波导出射端引入两个微腔, 通过光波与微腔发生共振, 形成类似于三个点光源干涉的出射光, 同时进一步提出波导出射端喇叭口干涉出射光定向辐射的设计。通过这种微腔喇叭口设计, 利用时域有限差分法分析结果表明光波实现很好的定向辐射, 并且辐射距离显著提高。     

基于双面金属包覆光波导的传感器温度特性研究及实验验证

双面金属包覆波导结构(SMCW)是由一层介质波导层被两层金属膜层上下包覆的一种新型波导结构; 本文基于金属层和介质层材料的热-光效应和热膨胀作用, 研究了双面金属包覆波导结构的温度特性. 计算分析的结果表明, 金属膜层的厚度、金属的介电系数、波导层的厚度及其介电常数几乎都与温度变化成比例, 同时, 对双面金属包覆波导结构的波导功能起主要影响的是介质层的厚度值随温度的变化. 本文分别在光谱模式和角度模式下研究双面金属包覆波导结构的反射特性, 并将其应用于基于双面金属包覆波导结构的传感器, 其灵敏度约为21.89 pm/K(光谱模式)和1.449×10^-3 rad/K(角度模式). 最后, 本文对角度模式的模拟分析进行了实验验证, 实验验证结果与模拟分析结果基本一致, 实验所用SMCW样品的平均灵敏度约为0.517×10^-3 rad/K, 与模拟分析的灵敏度结果同一量级. 双面金属包覆波导结构的传感器对温度非常敏感, 且该结构的物理构造简单, 成本低, 具有非常大的潜在应用价值.     

圆波导定向耦合器在高功率微波测量中的应用

介绍了大功率容量定向耦合器的设计、标定、测试与应用情况。以X波段圆波导定向耦合器为例,在9.2~10.2 GHz的频带范围内,基于小孔耦合理论优化设计的结构,其耦合度可以稳定在(55±2)dB以内,隔离度大于80 dB。在此基础上,设计加工了X波段圆波导定向耦合器并进行了标定测试,测试与仿真结果吻合较好,高功率微波实验证实了其具有较高功率容量,能够满足实验需求。该类圆波导定向耦合器已广泛应用于实验室高功率微波源的在线测量装置中。