Simultaneous determination of methylene blue and new methylene blue by slab optical waveguide spectroscopy and artificial neural networks

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. The simultaneous determinations of both MB and NMB were explored by flow injection SOWG spectrophotometric analysis and artificial neural networks (ANNs) for the first time. Concentrations of MB and NMB were estimated simultaneously with the ANNs. Results obtained with SOWG were compared with those got by conventional UV-visible spectrophotometry. (C) 2003 Elsevier Science B.V All rights reserved.

Study of adsorption of methylene blue and new methylene blue in liquid-solid interface by slab optical waveguide spectroscopy

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. Effect of pH on adsorption on MB and NMB was investigated. Binding rate constant analysis showed that both MB and NMB on bare SOWG demonstrates larger association constants than those on ODS-SOWG. Interactions of NIB and NMB on bare SOWG and ODS-SOWG were analyzed by molecular mechanics calculation method. The binding energy change was in the following order: ENMB-bare > EMB-bare > ENMB-ODS > EMB-ODS. (c) 2004 Elsevier B.V. All rights reserved.

Localized Solid-State Amorphization at Grain Boundaries in a Nanocrystalline Al Solid Solution Subjected to Surface Mechanical Attrition

Using high-resolution electron microscopy, localized solid-state amorphization (SSA) was observed in a nanocrystalline (NC) Al solid solution (weight per cent 4.2 Cu, 0.3 Mn, the rest being Al) subjected to a surface mechanical attrition treatment. It was found that the deformation-induced SSA may occur at the grain boundary (GB) where either the high density dislocations or dislocation complexes are present. It is suggested that lattice instability due to elastic distortion within the dislocation core region plays a significant role in the initiation of the localized SSA at defective sites. Meanwhile, the GB of severely deformed NC grains exhibits a continuously varying atomic structure in such a way that while most of the GB is ordered but reveals corrugated configurations, localized amorphization may occur along the same GB.

Transmission spectrum of a double quantum-dot-nanocavity system in photonic crystals

We investigate the optical transmission properties of a combined system which consists of two quantum-dot-nanocavity subsystems indirectly coupled to a waveguide in a planar photonic crystal. A Mollow-like triplet and the growth of sidebands are found, reflecting intrinsic optical responses in the complex microstructure.

Multiple quasi-phase-matching for enhanced generation of selected high harmonics in aperiodic modulated fibers

A technique for enhanced generation of selected high harmonics in a gas medium, in a high ionization limit, is proposed in this paper. An aperiodically corrugated hollow-core fiber is employed to modulate the intensity of the fundamental laser pulse along the direction of propagation, resulting in multiple quasi-phase-matched high harmonic emissions at the cutoff region. Simulated annealing (SA) algorithm is applied for optimizing the aperiodic hollow-core fiber. Our simulation shows that the yield of selected harmonics is increased equally by up to 2 orders of magnitude compared with no modulation and this permits flexible control of the quasi-phase-matched emission of selected harmonics by appropriate corrugation. (c) 2007 Optical Society of America.

Fabrication of microfluidic optical waveguides on glass chips with femtosecond laser pulses

We describe the fabrication of microfluidic channel structures on the surface of a borosilicate glass slide by femtosecond laser direct writing for optical waveguide application. Liquid with a variable refractive index is fed into the microchannel, serving as the core of the waveguide. We demonstrate that either a multimode or a single-mode waveguide can be achieved by controlling the refractive index of the liquid. (C) 2007 Optical Society of America

溶胶-凝胶光波导环形谐振腔的挥发性有机化合物传感特性

采用溶胶-凝胶法制作波导环形谐振腔, 讨论了环形谐振腔器件的传输特性。测量了在不同物质、不同体积分数的挥发性有机化合物(VOC)蒸气气氛下器件的传输光谱的敏感性。结果表明, 谐振波长随甲醇、乙醇、丙醇等醇类化合物, 以及丙酮、甲醛等蒸气体积分数的上升而向长波方向移动, 具有高的灵敏度, 且两者基本呈线性关系。其中, 对丙醇最敏感, 灵敏度达到1.403 pm/10-6。对甲烷和二甲苯也有微弱反应, 但是其灵敏度很低。也测量了水蒸气对传输谱特性的影响。观察到传输谱衬比度对不同挥发性有机化合物物质蒸气的不同敏

溶胶-凝胶条波导Sagnac环的乙醇蒸气传感特性

采用有机/无机混合溶胶-凝胶法制作条形光波导,并将条波导接入光纤Sagnac 环中,测量了输出光功率随环境气氛中乙醇蒸气体积分数变化的特性,表明在实验研究的范围内,输出信号与乙醇蒸气体积分数呈正弦变化。根据Sagnac环结构输出特性的基本关系,反映了溶胶-凝胶条波导在乙醇蒸气气氛下产生了双折射效应。观察到双折射相移与乙醇体积分数的亚线性关系。对实验数据拟合,计算了偏振相移的线性项和二次项系数,得到所制备的条波导的双折射对乙醇体积分数的响应为Δn≈4.4×10-2。测量了信号变化的时间演变特性,典型的上升和

长周期光纤光栅波导色散因子和有效折射率热光系数的测量

对串联的长周期光纤光栅(CLPFG)的透射谱特性进行了理论分析和实验研究。分析表明，长周期光纤光栅中纤芯模和包层模之间的马赫-曾德尔干涉效应导致在长周期光纤光栅谐振峰内的梳状滤波结构特性；其峰值位置和峰间距同串联区光纤的长度以及光纤的波导色散因子有关。测量了长周期光纤光栅的透射谱，并研究了其温度特性。根据测量数据，得到对应于1554nm波长处，所用单模光纤HE14模的波导色散因子γ为0．874；纤芯／包层有效折射率差的热光系数为4．8×10^-5℃^-1。并对这一测试方法和结果，以及长周期光纤光栅的应用进

Analysis of a second-order polarization-independent filter made of a single ring resonator and a Sagnac interferometer

A novel second-order polarization-independent filter made of a single ring resonator and a Sagnac interferometer (SRRSI) is proposed, and its filtering characteristics are investigated. By using birefringence in waveguide, a single ring resonator can be used to synthesize a filter with second-order response. Analytical formulas are derived for characteristics of the SRRSI varied with waveguide parameters.. such as the coupling coefficient; and the critical condition of a second-order Butterworth filter is given. The influence of loss in the ring resonator is also analyzed. (c) 2005 Elsevier B.V. All rights reserved.

有源波导环形谐振腔滤波特性分析

将掺铒有源波导材料引入环形谐振腔结构，从理论上分析了有源波导环形谐振腔的滤波特性。结果表明由于抽运光提供的增益补偿了腔内损耗，使得环形谐振腔满足临界耦合条件，实现对信号光的最佳陷波，同时发现通过改变抽运光功率，可以对精细度和带宽进行动态调谐。分析了铒离子掺杂浓度、信号光功率以及抽运光耦合系数对最佳陷波抽运功率的影响，为有源波导器件设计制作提供了理论依据。

平面弯曲波导耦合器的特性分析

根据耦合模理论和弯曲波导耦合器的结构特点,对平面弯曲波导耦合器的特性进行了分析,结果表明弯曲波导耦合器的弯曲半径和最小间距两个可调变量,增加了波导器件设计的灵活性;同时由于等效耦合长度的调制作用使得弯曲波导耦合器在波分复用/解复用中比平行直波导耦合器具有更大的复用带宽;分析了弯曲半径和最小间距对弯曲波导耦合器复用带宽的影响,为实际波导器件的设计制作提供了一定的理论依据.

低损耗有机无机混合溶胶凝胶波导的实验研究

利用有机无机混合的溶胶凝胶方法在硅基底上制备波导薄膜．采用正硅酸四乙酯和苯基三乙氧基硅烷作为反应先驱物，利用旋涂的方法成膜，对其折射率，传输损耗以及条形波导的光刻、刻蚀特性进行了研究．测量了波导薄膜折射率随成分变化的关系．实验表明，该方法工艺简单，可以获得具有较低损耗的波导薄膜．测试得到632．8nm波段的损耗系数为0．23dB／cm．采用ICP刻蚀工艺获得了较为平整的条形波导．

利用有机-无机溶胶-凝胶方法制备平面波导环形谐振腔

采用简单的有机一无机混合的溶胶一凝胶方法制备了折射率在一定范围内可调的波导材料，并利用其制备了平面波导环形谐振腔器件。波导结构呈现倒脊形，其制备工艺首先是利用感应耦合等离子体刻蚀技术（ICP）在二氧化硅衬底上刻蚀波导结构的凹槽，然后再沉积波导薄膜。利用光谱仪对器件的传输特性进行了测量，观测到具有10dB对比度，自由光谱范围0．182nm周期性谐振现象，结合环形谐振腔的传输特性，得到环形腔具有较低的传输损耗1．7dB／cm。同时对环形谐振腔的温度特性进行了测量，得出波导材料的热光系数为-1．54×10^-4