Modeling of waveguide UV-induced Bragg gratings with arbitrary apodization function: Tools for designing high-performance related devices

We present a semi-analytical modeling suitable for the investigation of the spectral characteristics of UV-waveguide Bragg gratings (UV-WBGs) having arbitrary apodization function and extending both in the film layer and in the overlayer. The modeling is based on a proper combination of coupled mode theory and transfer matrix formalism and provides a powerful tool for designing and simulation of complex UV-grating based structures. The results of a detailed investigation of UV-WBGs in doped silica based channel optical waveguides are presented and critical issues for upgrading the performances of related device are discussed. Validation of the modeling is provided by means of an extensive comparison between theoretical and experimental results relevant to UV-WBGs realized in phosphorous (P)- and boron (B)-doped silica based waveguides.     

Coaxial waveguide gyro-peniotron

A coaxial waveguide gyro-peniotron with largeorbit beam is proposed. The linear thoery of 3-D model is given to describe this device. The influences of the beam radius and beam current on the normalized growth rate are discussed in terms of numerical analysis.     

脊形波导中导模传输与损耗的分析与计算

本文运用有效折射率法把脊形波导化成等效二维平板波导后,再运用微分法求出弱吸收情况下波导模的吸收损耗,其方法简便,精确度高.     

Selective area rare-earth doping of planar glass samples for monolithic integration of optically passive and active waveguides

Successful demonstration of selective area doping of planar glass samples for monolithic integration of optically passive and active devices on a single chip is presented. Salt solution of erbium was delivered onto pre-sintered germano-silicate samples via a syringe. The samples were then consolidated to form dense glass layers containing regions doped with rare earth. Erbium tri-chloride solution, 0.1 M, was used during the solution doping phase, with the resulting erbium atomic percentage ranging from more than 0.1-0.4%, increasing linearly with the number of drips applied.     

Analysis for Transmission Characteristics of Closed Trapezoidal-Groove Waveguide with Boundary Element Method

In this paper, the cut-off and dispersion characteristics of a new kind of closed trapezoidal-groove waveguide that has more advantages than open groove waveguides are analyzed with the help of the boundary element method, the relationship between cut-off wavelengths and variations of guide's relative sizes is discussed in detail. The calculated results are in good agreement with those in the relevant reference. So, the obtained conclusions are very important in theoretical studies and actual applications of closed trapezoidal-groove waveguides for millimeter and submillimeter waves.     

Crosstalks of two-waveguide and three-waveguide directional couplers

Crosstalks of two-waveguide and three-waveguide directional couplers are analyzed mathematically based on the relationship between the coupled mode and the normal mode. Numerical techniques such as the finite-difference method and the beam propagation method are employed to confirm the validity of the derived expressions. The calculation results show that two-waveguide directional coupler is superior to any type of three-waveguide couplers from the practical viewpoint of the crosstalk and the coupling length.     

Analysis of Ti:LiNbO3 zero-gap directional coupler for wavelength division multiplexer/demultiplexer

For the purpose of multichannel integrated-optical wavelength division MUX/DEMUX design, the wavelength tuning method of Ti:LiNbO₃ zero-gap directional coupler is analysed by effective-index based matrix method (EIMM). In this method, first, the 2D refractive index profile of the Ti:LiNbO₃ zero-gap directional coupler is transformed into lateral 1D effective-index profile by WKB method. Finally, matrix method is applied to this effective-index profile and the propagation constants are computed from the resonance peaks of the excitation efficiency versus propagation constant characteristics. It has been shown that the channel wavelength tuning can be achieved by varying the Y-branching angle at the input and output of the device or by a slight variation of two-mode-section length. The method of electro-optic fine tuning of the channel wavelength and channel separation of the device has also been investigated. A cascaded structure with proper parameters for four-channel application is also simulated and the results are presented.     

On the two methods of kinetic theory of ECRM

The kinetic theory based on the expansion of local field in the guiding center coordinate system, presented by paper[1]–[3], has successfully developed into a theoretical system. The mathematical background and physical explanation of setting up the guiding center coordinate system is expounded in the paper. By using the methods of the guiding center and waveguide coordinate systems respectively, the same dispersion equations for interaction of an axially symmetrical single momentum electron beam with TE_mn field in the circular waveguide are rigorously derived. A number of mistakes in paper[4] are indicated as well.     

In situ monitoring of the H concentration change near an electrode surface through electrolysis using slab optical waveguide pH sensor

The H⁺ concentration change was monitored near an electrode surface through an electrolysis using a slab optical waveguide technique. Indium tin oxide transparent electrode modified by porous insulating polymer to which methyl red was covalently immobilized was used as a guiding layer, and the absorbance change of the polymer film was monitored. H⁺ generation at the vicinity of the electrode through the oxidation of ascorbic acid could be monitored by this technique.     

质子交换MgO:LiNbO3波导的双层结构

本文报导MgO:LiN_bO₃质子交换波导X射线双晶衍射和红外吸收的实验结果。这些结果表明质子交换波导由浅表面层和深表面层构成。浅表面层是一个连续应变层,有着大量随机排列的O—H—O形式的缔合OH^-基团。深表面层是一个均匀应变层,其内H⁺以自由OH^-基团形式出现。质子交换波导折射串不稳定性与双层结构中的结构驰豫密切相关。通过对质子交换过程的分析,提出两条避免双层结构的途径,其一为降低交换剂中的H⁺浓度,另一条是采用有限源工艺。