Birefringence suppression of UV-induced refractive index with grooves in silica-based planar lightwave circuits

An effective method for suppressing the birefringence of a UV-induced refractive index change is demonstrated for phase trimming of waveguides in planar lightwave circuits. By employing grooves on both sides of the waveguide to control the UV-induced strain, a significant reduction is achieved from 1.46/spl times/10/sup -4/ to 0.11/spl times/10/sup -4/ in the UV-induced birefringence for a /spl pi/ phase shift averaged between the TE and TM modes in a 2 mm-long waveguide.     

Trimming phase and birefringence errors in photosensitivity-lockedplanar optical circuits

A strong and stable photosensitivity response was permanently locked into hydrogen-loaded Mach-Zehnder planar waveguide circuits by 248-nm KrF-laser preirradiation. The photosensitivity enhancement survived thermal annealing up to 225 °C. Post-laser trimming at 248 nm induced an unsaturated refractive index increase of 0.002, and a birefringence change of ▵n ~ 0.0001. This combination of photosensitivity locking and post-laser tuning affords wide latitude for precise and stable tuning of waveguide phase errors and birefringence     

激光微调在光通讯波导器件研制中的应用

目前激光微调在光通讯波导器件的研制方面已得到了应用。本文运用激光微调在波导器件上进行了实验,其中以波导环形器和马赫—曾德尔干涉仪为例,具体讨论了激光微调技术在控制波导双折射方面所表现出的高效,简易,实用等优点。     

Birefringence control of silica waveguides on Si and itsapplication to a polarization-beam splitter/switch

A novel polarization-beam splitter/switch with a Mach-Zehnder interferometer configuration was fabricated using a silica-based planar lightwave circuit (PLC) on a silicon substrate. The polarization-beam splitter/switch was realized by accurately controlling the waveguide birefringence and the phase state by laser trimming two kinds of stress-applying amorphous silicon film with widths of 50 μm and 95 μm. Fiber-waveguide-fiber insertion loss of 0.5 dB and crosstalk attenuations of over 25.6 dB were attained     

128-channel polarization-insensitive frequency-selection-switchusing high-silica waveguides on Si

A 128-channel polarization-insensitive frequency-selection-switch (FS-SW) with 10-GHz frequency spacing is discussed. The FS-SW was fabricated on Si using low-loss GeO₂-doped high-silica waveguides, and its frequency-insensitive operation was attained by the laser trimming adjustment of a-Si film which controls waveguide birefringence. The fiber-to-fiber loss of the transmitted channel was 6.7 dB in the pigtailed FS-SW and the total crosstalk level was less than -13 dB. By using this FS-SW, a 100-channel optical frequency division multiplexing (FDM) transmission-distribution experiment at 622 M b/s over a 50-km fiber length was achieved     

Trimming of polymer waveguide Y-junction by rapid photobleaching for tuning the power splitting ratio

We present a novel post-fabrication laser trimming technique to adjust the power splitting ratio of rib waveguide Y-junctions made in thermally crosslinked electrooptic polymers. The trimming is based on the index change due to photobleaching, and it takes only a few seconds. An adjustable range of the splitting ratio as wide as /spl plusmn/20% is achieved with less than 0.2 dB of excess loss. This in situ trimming technique is effective for both the TE and TM modes of the waveguide and is very suitable for automated device processing.     

Birefringence in curved single-mode optical fibers due to waveguide geometry effect--Perturbation analysis

The field deformation in curved step-index single-mode circular fibers and the birefringence induced by the curved waveguide geometry are analyzed by a perturbation method. We find that the values of the birefringence are proportional toa^{2}/R_{0}^{2}and are much less than those induced by stress. A square optical waveguide is also investigated. We find birefringence values of roughly the same order of magnitude as those for the circular waveguide.     

Double-layered magnetooptic channel waveguide for waveguideisolator application

TE-TM mode conversion based on the nonreciprocal Faraday effect for waveguides fabricated by liquid-phase epitaxially grown (YBiCa)₃Fe₅O₁₂ films is discussed. The phase mismatch is controlled by constructing a double-layer channel waveguide with an intermediate cladding layer of refractive index slightly lower than the core. Care must be taken to compensate any birefringence of materials, e.g. stress- and growth-induced birefringence. It is shown that such a structure is effective in decreasing the effect of waveguide shape deformation on the phase-matching degree. The analysis of the double-layered channel waveguide and experimental results are described     

Elimination of PD-/spl lambda/ at all output ports of silica-based AWG

It is shown that the polarisation dependent wavelength shift (PD-/spl lambda/) of a silica-based arrayed waveguide grating (AWG) is proportional to its output port location as a result of the birefringence in a slab waveguide. This PD-/spl lambda/ was eliminated to less than 0.01 nm by inserting a half waveplate across the slab waveguide.     

InP/InGaAsP脊波导的单模特性与偏振特性研究

以InP/InGaAsP脊形波导结构为研究对象,采用有限元算法(FEM),系统地仿真分析了在固定芯层厚度的情况下,不同脊高和脊宽条件下脊形波导的单模特性和偏振特性.在芯层厚度一定的情况下,脊宽越窄,刻蚀深度越浅,波导的传输模式越接近单模.在深刻蚀情况下,脊波导模双折射系数受到脊宽的影响较大,波导的偏振不敏感性较差;在浅刻蚀情况下,模双折射系数(△n=nTE-nTM)受到脊宽和脊高的影响较为微弱,稳定在1.2×10-3.相关仿真和分析为基于InP/InGaAsP脊波导的光电子器件的结构设计提供了一定的理论支持.     

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.     

Birefringence in benzocyclobutene strip optical waveguides

We report the fabrication of benzocyclobutene strip optical waveguides and the measurement of their birefringence properties. To take into account the stress-induced birefringence in the waveguide, we generalize the formulas reported previously for the analysis of strip waveguides. Our experimental results are shown to agree closely with the theoretical calculation. The condition for achieving zero modal birefringence by control of the aspect ratio of the strip of the waveguide is highlighted. The dependence of the birefringence in the waveguides on the temperature is also measured and discussed.     

SiO2/Si波导应力双折射数值分析

采用有限元法对SiO2/Si掩埋光波导制备工艺中的应力变化进行了系统的分析，在此基础上，应用有限差分束传播法(FDBPM)对应力光波导的双折射进行了计算．结果表明上包层的玻璃化过程是SiO2/Si波导形成水平方向和垂直方向应力差的主要原因，相应的应力双折射系数Ｂ在10~－4量级．进一步的分析表明上包层B，P重掺杂可明显减小波导的双折射系数．     

SiON对Si基SiO2 AWG偏振补偿的数值分析

采用全矢量交替方向隐含迭代方法系统分析了高折射率SiON薄膜对Si基SiO2阵列波导光栅中波导应力双折射的影响.分析结果表明在芯区上或下表面沉积SiON薄膜可以明显减小Si基SiO2阵列波导光栅(AWG)中波导的应力双折射,但这两种补偿方法容易使模场偏移中心位置,不利于波导与光纤的耦合.理想的补偿方法是在芯区上下同时补偿,可减小模场偏移,并用该方法设计了偏振无关的16通道AWG.     

SiON对Si基SiO_2AWG偏振补偿的数值分析

采用全矢量交替方向隐含迭代方法系统分析了高折射率 Si ON薄膜对 Si基 Si O2 阵列波导光栅中波导应力双折射的影响 .分析结果表明在芯区上或下表面沉积 Si ON薄膜可以明显减小 Si基 Si O2 阵列波导光栅 (AWG)中波导的应力双折射 ,但这两种补偿方法容易使模场偏移中心位置 ,不利于波导与光纤的耦合 .理想的补偿方法是在芯区上下同时补偿 ,可减小模场偏移 ,并用该方法设计了偏振无关的 1 6通道 AWG.     

Highly birefringent and monomode GaAlAs-GaAs planar optical waveguide

A novel optical waveguide exhibiting a layered core region is proposed. Owing to the original design of the core stack and form birefringence in the multilayer, a waveguide supporting both TE and TM lowest-order modes with high confinement has been obtained. It has been designed, fabricated, and characterized and presents a modal birefringence greater than 0.01, which is in good agreement with the calculated values.     

硅基二氧化硅波导的应力和偏振相关性的数值分析

使用有限元方法分析了硅基二氧化硅光波导的应力分布,结果表明波导主要受横向压应力影响,而且应力主要集中在芯区和包层的界面附近.根据波导的应力分布,得出波导的折射率分布,并使用ADI全矢量方法求解出波导的模式折射率.比较考虑应力和未考虑应力的波导模式折射率可以得出:波导的双折射效应主要是由于波导应力引起的,阵列波导光栅的偏振相关与中心波长的漂移是受阵列波导的应力分布的影响.     

Integrated optical waveguide polarizer based on photobleaching-induced birefringence in an electrooptic polymer

A TE-pass waveguide polarizer is fabricated by utilizing the photobleaching-induced birefringence at room temperature in an electrooptic polymer. The polarizer consists of the photobleached waveguide supporting only TE mode, which is integrated in the middle of the etched rib waveguide supporting both TE and TM modes. It has a simple structure and requires no high temperature process like poling. The measured polarization extinction ratio is about 21 dB at the wavelengths of 1.3 and 1.55 /spl mu/m, and the estimated excess loss is about 0.4 dB.     

Low-loss polymeric optical waveguides fabricated with deuteratedpolyfluoromethacrylate

Deuterated polyfluoromethacrylate which has high transparency, low birefringence and good processability was newly synthesized for use as optical waveguide materials, and both single-mode and multimode optical waveguides were fabricated using the polymer. The propagation loss and waveguide birefringence of the single-mode waveguides were as low as 0.10 dB/cm and -5.5×10^-6 at 1.31 μm, respectively. The propagation losses of the multimode waveguides were less than 0.02 dB/cm at both 0.68 and 0.83 μm, and 0.07 dB/cm at 1.31 μm     

Electrooptic polymer modulators operating in both TE and TM modes incorporating a vertically tapered cladding

We propose a modified electrooptic (EO) PMMA polymer waveguide structure supporting both TE and TM modes in spite of the large birefringence induced by the poling. A vertically tapered structure is employed to connect a single-mode rib waveguide and a confinement-enhanced rectangular buried waveguide. This waveguide structure can be easily fabricated by a two-step reactive ion etching (RIE) process with a shadow mask. To demonstrate TE/TM confinement and single-mode operation, Mach-Zehnder intensity modulators are fabricated by incorporating the proposed waveguide structure. The extinction ratio is better than -15 dB, which proves the single-mode operation. Half-wave voltages for TM and TE modes are 6 and 24 V, respectively.