聚合物Y分支脊形波导的单模条件

有机聚合物光波导近年来成为研究的热点,它为实现下一代的光电集成回路提供了另外一种选择。它所具有的一系列优点如下:(1)与传统的材料相比,有机聚合物光波导容易在各种衬底上制作,其制作成本也得以降低,并且使得与有源器件如激光器、调制器、探测器的单片集成成为可能;(2)有机聚合物波导材料的折射率可以进行调整以满足耦合损耗和弯曲损耗的折中选择;(3)此外,有机聚合物的热光系数比SiO₂大一个数量级,而其导热系数却比SiO₂和Si小得多。有机聚合物Y分支是强度调制器和光开关等器件的重要组成。光波导器件在和单模光纤一起使用时要求其实现单模传输,这样可以减少耦合损耗。利用变分有效折射率法计算了聚合物Y分支脊形波导的光场分布。变分有效折射率法是变分法(VM)和有效折射率法(EIM)的结合,它结合了两种方法各自的优点,能够很精确地模拟光场分布情况。利用变分有效折射率法验证了满足单模传输的脊形波导结构参数:芯层厚度为1.5μm,脊高为0.2μm,脊宽为5μm。     

聚合物脊形光波导的变分有效折射率法分析

聚合物脊形光波导是聚合物集成光电子器件的重要构成单元.利用有效折射率法计算聚合物脊形光波导的横向折射率分布及有效折射率,将各区域中的光场分布近似用分段函数表达.基于导模满足的标量波动方程,利用变分法确定变分参量,以求得准确的横向光场分布.对聚合物脊形多模光波导基模和高阶模的色散特性与横向场分布进行分析,研究了波导结构参数对色散特性的影响,计算出TM基模和高阶模的光场分布,得出了聚合物脊形光波导的单模传输条件.研究表明,该方法计算量小、精度高,对聚合物光电子器件中脊形光波导的理论分析与设计优化提供了简单高效的方法.     

Design and fabrication of electro-optic waveguides with self-assembled superlattice films

This paper presents a strategy for fabricating low loss waveguide devices based on high electro-optic (EO) coefficient self-assembled superlattice (SAS) films, a new sort of polymeric films grown on SiO₂ film and coated with other polymeric films to form multi-layer EO waveguides structure without electric field poling. Firstly, the optical propagation loss induced by the absorption of electrodes is simulated and optimized to obtain both the low optical loss and the low drive voltage. Then this paper gives the scanned electron microscopic (SEM) images of the fabricated devices, the simulated and experimental images of the single guided mode, and the measured optical propagation loss of the EO waveguide devices of 1.0 dB/cm. Finally, the very great agreement between the simulated and measured results of propagation loss of devices is observed.     

Amplification properties of Tb (III) green emission in polymeric waveguide doped with Tb-Al nanocluster

This paper describes optical amplification properties in a polymeric waveguide doped with Tb-Al nanoclusters. The Tb-Al nanocluster is a promising fluorescent material for polymeric waveguides, which can be uniformly dispersed in polymer matrices while restraining the concentration quenching of Tb³⁺. Under the continuous optical pumping by 488 nm laser light, optical amplification for the green emission of Tb³⁺ was achieved. The optical gain coefficients were estimated to be as high as 0.25 and 0.56 mm⁻¹ at the Tb-Al nanocluster concentrations of 4.5 and 5.0 wt%, respectively. Taking into account our previous works for the polymeric waveguide doped with Eu-Al nanocluster, the rare-earth-metal nanocluster is believed to be a promising candidate for various photonic applications such as multicolor polymer lasers and waveguide-type optical amplifiers.     

聚合物Mach-Zehnder脊形波导的优化设计

 利用变分有效折射率法计算了TE基模和高阶模的光场分布,计算结果表明,该方法计算量小,精度高,为聚合物集成光电子器件中脊形光波导的理论分析与优化设计提供了简单高效的途径。利用有限差分束传播法对Mach-Zehnder波导的传播及损耗特性进行了理论分析,得到了不同Y分支角、波导宽度、波导间距时波导传输功率与距离的关系,优化得到的结构参数为：Y分支角1.1°,脊宽5 μm,波导间距20 μm。     

Temperature dependence of low loss polymeric AWG

We investigate on the variation of loss and temperature dependence of a polymeric arrayed waveguide grating (AWG) depending on its substrate, by fabricating 16-channel polymeric AWGs with various substrate conditions. Insertion loss for a polymeric AWG on a silicon substrate is measured as low as 3.1 dB. The temperature-dependent wavelength shift for a polymeric AWG detached from the substrate is maintained within 0.1 nm from 20 to 80 °C. But we observe a degradation of insertion loss and a little instability in wavelength characteristics both for the detached polymeric AWG and for a polymeric AWG on a polymer substrate. We investigate on those optical properties of the polymeric AWGs based on measured thermal expansion properties of the polymers.     

Simple process for fabricating a monolithic polymer optical waveguide

A simple and economical fabrication process for a monolithic polymer optical waveguide in which different materials are serially grafted is proposed and demonstrated. A cladding layer with a waveguide core groove is fabricated by microtransfer molding. An epoxy resin solution is spin coated onto the cladding before selective photoexposure to form a transparent waveguide core. An optical functional polymer solution is then spin coated to form a serially grafted waveguide structure. Thus two types of polymer fill the groove to realize a monolithically integrated waveguide. Controlling the groove shape results in a flat surface. A low connection loss between the two polymers, less than 0.01 dB/point, is obtained.     

Integrated optical proximity microsensor

This paper presents the design, simulation and experimental results of an integrated proximity sensor manufactured on silicon substrate. The sensor was designed for microrobotic applications like integration into a microgripper arm or detection of the position of gripper arms relative to an object. The structure is based on an SU8 polymeric optical waveguide splitted into three arms, integrated with a multielement photodetector on silicon substrate. Each element of the photodetector is a metal-semiconductor-metal (MSM) photodiode with Ti/Al Schottky interdigitated electrodes.The operation principle of this sensor consists in the light coupling in the central arm of the optical waveguide, interaction with the object (reflection) of the radiation which exits from this principal arm, the coupling of the “affected” radiation which comes back through the end of the waveguide and its splitting into three arms of the optical waveguide. From the optical waveguide, the light is coupled in photodiode and the photogenerated carriers are collected to the electrodes giving the electrical signal which is read and processed in real time.The optimal parameters of the waveguide (width, thicknesses of the core and the claddings) of the photodetector and the coupling between them were defined by simulation, using FDTD and BeamProp method (Opti FDTD software). Our microsensor can detect the position of an object in the range of 0-300 μm, as position sensor and with high precision in the range of zero to twice the wavelength, as proximity sensor.     

The Influence of Defects on the Propagation Light within Polymeric Optical Waveguides Studied by Polarized Near-Field Scanning Optical Microscopy

We have developed a polarization-preserving near-field scanning optical microscopy (NSOM) optical fiber probe and with it observed the influence of defects and weak stresses on a propagation light within polymeric optical waveguides. To characterize the influence, we intentionally printed an indentation in the vicinity of the waveguide and then evaluated the resulting influence using polarized guide-collection-mode NSOM images taken around the indentation. When transverse magnetic polarized light enters a waveguide, the light intensity becomes greater on the near side of the indentation than on the far side, as measured by a linearly polarized component perpendicular to the direction of light propagation. The most probable cause of this phenomenon is microdefects generated by the printing of the indentation. The polarized NSOM technique is useful in searching for small defects or stresses within integrated photonic devices.     

基于有机聚合物的M-Z波导设计

M-Z光波导是有机聚合物电光调制器的重要结构单元.将有效折射率法与二维差分束传播法相结合,利用有效折射率法计算了聚合物脊形波导的横向折射率分布及有效折射率.由Maxwell方程出发,结合辐射透明边界条件,采用Crank-Nicholson差分格式,得出有限差分束传播法的计算格式.通过对M-Z型波导结构中TM模的传播及损...     

聚合物电光调制器中M-Z波导TM模分析

M-Z光波导是聚合物电光调制器的重要结构单元。利用有效折射率法计算聚合物脊形波导的横向折射率分布，将三维光波场传播简化为二维传播。从导模满足的标量波动方程出发，结合透明边界条件，采用Crank-Nicholson差分格式，得出有限差分束传播法的基本计算格式。通过对M Z型波导结构中TM模的传播及损耗特性进行理论分析，系统地研究了脊宽、分支角等结构参数对损耗的影响。研究表明，有效折射率法与二维有限差分束传播法的结合可以较好地解决脊形M Z波导的设计问题。该方法具有精度高、计算量小及效率高等优点，为聚合物电光调制器的制备提供了理论依据。     

聚合物波导M-Z调制器TM模的泰勒级数展开法研究

根据聚合物脊型波导的结构特点,利用有效折射率法求出其横向折射率分布,将三维传播转化为二维传播,并从标量波动方程出发,在傍轴近似的情况下,采用Crank-Nicholson差分格式,得到了泰勒级数展开法基本计算格式,并对算法进行了适当优化;通过对Mach-Zehnder光波导TM模的模拟,分析了各种参数对损耗的影响。结果表明：泰勒级数展开法具有精度高、稳定性好、算法简单、易于编程等优点,是一种比较理想的光波导数值分析方法,可为聚合物电光调制器的设计制作提供理论参考。     

Proton beam writing of Nd:GGG crystals as new waveguide laser sources

Focused proton beam writing has been utilized to fabricate optical channel waveguides in Nd:GGG crystals. The 1?MeV proton beam irradiation creates a local modified region with positive refractive index changes at the end of the proton trajectory, in which the channel waveguide could confine the light field in a symmetric way. Room-temperature laser emission has been achieved at 1063.7?nm, with absorbed pump power of 61?mW (at 808?nm). The obtained slope efficiency of the Nd:GGG waveguide laser system is as high as 66%, which is, to our best knowledge, the highest value for integrated lasers from ion beam processed channel waveguide systems.     

Design and analysis of nano-deep corrugated waveguide grating-based dual-resonant filters in visible and infra-red regions

A theoretical analysis of nano-deep corrugated long-period waveguide gratings on a SU-8 polymer-based channel waveguide with NOA61 optical epoxy coated upper- and lower cladding is presented. The transmission spectra of the gratings show strong rejection bands both at visible (at wavelength region of 450?460 nm) and infra-red (at wavelength region of 1530?1540 nm) regions when a grating period of ?68 μm with optimized grating tooth height is considered. Phase-matching graphs are studied to find the relationship between resonance wavelength and grating period. These results show that the grating parameters significantly affect the characteristics of transmission spectra as well as the resonance wavelength of the grating. Long-period waveguide grating-based band pass filter made by use of same polymer materials are also designed and analyzed. These types of waveguide grating-based filters can widely be used for visible and infra-red wavelength sensing applications.     

Traveling－Wave Electrooptical Modulator on Polymeric Film with Reversal Poling Structure

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Polymeric distributed-feedback resonator with sub-micrometer fibers fabricated by two-photon induced photopolymerization

The authors observed amplified spontaneous emission (ASE) action with an ultra-low threshold under optical excitation from an active polymeric distributed-feedback (DFB) resonator which consists of sub-micrometer fiber grating. A dendrimer was used to modify the laser dye and increased its concentration up to 4.95 wt. % in the photocured resin. The DFB resonator was fabricated by using two-photon induced polymerization (TPIP) technique. The ASE at 556 nm was observed with a threshold of 0.30 μJ/pulse due to fourth-order diffraction feedback of the optical gain. This DFB could be expected to open a way for the fabrication and application of microscale polymeric mirrorless laser. PACS 42.70.-a; 81.40.Tv; 82.35.Ej; 82.50.Pt; 42.60.Da     

Low-loss polymeric optical waveguides with large cores fabricated by hot embossing

A simple low-cost method of fabricating polymeric optical waveguides with large core sizes for plastic optical fibers is presented. The waveguides are fabricated by hot embossing with an ultraviolet-cured epoxy resin stamper. The stamper is fabricated by replication of a rectangular groove mold that is made from silicone rubber replicated from a ridged original silicon master. The master is fabricated by anisotropic etching of (110) single-crystal silicon. Optical waveguides with large core sizes of 100-500 microm have been fabricated, and a low propagation loss of 0.19 dB/cm at 650 nm was achieved.     

Asymmetrical off–on switches for crosstalk reduction in switching networks

An off–on switching scheme is introduced which blocks a waveguide path in the passive off-state and transmits the signal in the active on-state. The operating principle is based on the self-diffraction of a narrow guided beam when it escapes from a waveguide with two-dimensional confinement into a region of appropriate length with basically one-dimensional confinement. In particular, a remaining interface of the initial waveguide superimposes reflection, which in sum results in a very efficient asymmetrical blow out of the guided power. In the active on-state, low-loss waveguiding is sustained when an electrode causes an appropriate refractive index change, e.g., due to the thermo-optical effect. Thus, the signal is received in the output waveguide, the identical counterpart of the input guide. The switching behaviour is almost binary with minimal wavelength dependence. This makes the device useful for switching and modulation in a multi-wavelength optical network. For a realistic polymeric waveguide configuration, simulations indicate on-off signal ratios of >30 dB. This satisfies the requirements for crosstalk reduction in switching networks.     

Stress reduction in planar waveguide using polymer top layer

Planar optical waveguides consisting of layers from different materials created at elevated temperatures usually exhibit substantial stresses. By controlling the layer thickness of polymeric top layer on planar waveguide structures, it is possible to use very thin layers for stress compensation, significantly reducing required deposition times. It is possible to reduce birefringence within planar device by controlling top polymer layer thickness with thermal expansion coefficient greater than silica or PMMA.     

聚合物阵列波导光栅复用器关键技术的研究

介绍了阵列波导光栅(AWG)复用器的工作原理;运用光栅衍射理论和马卡提里近似法,对中心波长为1.55 μm,波长间隔为1.6 nm的聚合物AWG进行参量设计,通过数值模拟验证了设计的正确性.用甲基丙烯酸甲酯类聚合物对AWG的制备工艺进行了研究,用铝作掩模制作了聚合物光波导,测试结果表明在1.55 μm处波导实现单模传输.