Optical path design and evaluation in Tm doped glass channel waveguide for S-band amplification

To achieve high-gain S-band waveguide amplifiers and promote the practicality of integrated signal amplification devices, bent waveguide structures based on Tm³⁺ doped germanate glass substrate have been designed. Using simulated-bend method, the optimal radius for the curved structure is offered to be 1.90 cm with a loss coefficient of 0.04 dB/cm, as the substrate size is minimally schemed. For the folded-spiral waveguide, the internal gain at 1482 nm is derived to be 13.01 dB, which is higher than the values of 8.21 and 4.22 dB in the U- and S-bend waveguides, respectively, and nearly three times higher than that of the straight one. Simulation results indicate that the optical path design is attractive in realizing the high gain of Tm³⁺ doped germanate glass channel waveguides for practical S-band amplification.     

用极坐标下的广角光束传播法计算分析弯曲波导

采用了极坐标下的广角BPM(Beam Propagation Method)对弯曲波导进行了计算模拟,并与极坐标下近轴BPM方法进行了比较,取得很好的结果.     

Bent Functions, Partial Difference Sets, and Quasi-Frobenius Local Rings

Bent functions andpartial difference sets have been constructed from finite principalideal local rings. In this paper, the constructions are generalizedto finite quasi-Frobenius local rings. Let R bea finite quasi-Frobenius local ring with maximal ideal M.Bent functions and certain partial difference sets on M } M are extended to R } R.     

Control of symmetry in active cationic ansa-zirconocene species: catalyst preparation, characterization and ethylene-norbornene copolymerization

New bis-hydrocarbyl complexes of methylene bridged ansa-metallocenes [H₂C(C₅Me₂H₂)₂]ZrR₂ {R = Me (1), CH₂Ph (2), CH₂SiMe₃ (3), Ph (4)} have been prepared. They form catalytically active intermediates with borane or borate depending on solvent and Zr-R group. Specifically, [H₂C(Me₂C₅H₂)₂]Zr(CH₂Ph)₂ (2) produced an ion pair upon treatment with B(C₆F₅)₃ whereas [H₂C(Me₂C₅H₂)₂]Zr(CH₂SiMe₃)₂ (3) produced a zwitterionic species, identified by ¹H, ¹³C, and ¹⁹F NMR spectroscopy. Copolymerization of ethylene and norbornene for the metallocene dichloride/MAO and bis-hydrocarbyl complex/borate systems was compared.     

Bonding and Reactivity in RB-As R Systems(R=H,F,OH,CH_3,CMe_3,CF_3,SiF_3,BO): Substituent Effects

Density functional theory-based calculations have been carried out to study the bonding and reactivity in RB-As R(R=H,F,OH,CH3,CMe_3,CF_3,SiF_3,BO)systems.Our calculations demonstrated that all the studied systems adopted bent geometry(DR-B-As≈180°andDB-As-R≈90°or less).The reason for this bending was explained with the help of a valence-orbital model.The potential energy surfaces for three possible isomers of RB-As R systems were also generated,indicating that the RB-As R isomer was more stable than R_2B-As R when R=SiF_3,CMe_3,and H.The B-As bond character was analyzed using natural bond orbital(NBO)and Wiberg bond index(WBI)calculations.The WBI values for B-As bonds in F3Si B-As SiF_3 and HB-As H were 2.254 and 2.209,respectively,indicating that this bond has some triple-bond character in these systems.While the B centers prefer nucleophilic attack,the As centers prefer electrophilic attack.     

On the coefficients of binary bent functions

We prove a 2-adic inequality for the coefficients of binary bent functions in their polynomial representations. The 2-adic inequality implies a family of identities satisfied by the coefficients. The identities also lead to the discovery of some new affine invariants of Boolean functions on .

     

弯曲光纤针尖及其法向力压电探测技术

本文介绍一种弯曲光纤针尖及其法向力压电探测的新技术.与目前普遍采用的方法不同,弯曲针尖的制作是先利用电阻丝加热,将光纤弯曲成所需的角度,然后再在缓冲氢氟酸中腐蚀成针尖,得到曲率半径为300μm,弯曲角度为120°,长度为500μm的弯曲针尖.同激光或电弧熔拉、弯曲的方法相比,这种方法工艺简单,成本低廉.由弯曲针尖与蜂鸣器压电片组成的悬臂,利用压电片的正、逆压电效应实现弯曲针尖法向力的非光学法探测.实验表明,这种弯尖法向力的探测较直尖切变力具有更高灵敏度,探测距离提高了一倍以上,给实际应用带来很大的便利.     

Experimental and DFT generated Raman study of two bent-core monomeric liquid crystalline compounds

The temperature dependence Raman spectra of two liquid crystalline compounds defined by the chemical formula of 3,5-difluoro-4?-(4-pentylcyclohexyl)-(1,1?-biphenyl)-4-carbonitrile and 3,4,5-trifluoro-4?-(4-pentylcyclohexyl)-1,1?-biphenyl is being first reported in this study. These compounds are bent-core monomers and their bent nature has been verified by the Density Functional Theory (DFT). The temperature-dependent Raman spectroscopy has been widely used in understanding the effects of temperature-based phase transitions on the molecular vibrations. The same spectroscopic technique; helps to understand various phase transitions temperature in the liquid crystalline compounds (LC) and also their molecular arrangements during the phase transitions. This study has successfully revealed the nature of intermolecular interactions between the investigated compounds during the phase transitions and the correlation between the observed Raman spectra and the measurement temperature. The contributions of different types of chemical bonds in the investigated LC compounds to their recorded Raman spectra have also been discussed in detail. In predicting the observed Raman spectra, the theoretical Raman spectra obtained from the DFT calculation was used as a reliable tool. In the light of the calculated data, the peak position, line width, and integral intensity data for each band in the observed Raman spectra were reported.     

Mesomorphic and photophysical behaviour of 1,3,4-oxadiazole based hockey stick reactive mesogens

New hockey stick mesogens derived from 1,3,4-oxadiazole as a bent-core unit have been synthesised. The molecules resemble hockey stick shape due to the presence of two arms containing a different number of phenyl rings attached with the 1,3,4-oxadiazole bending unit. The shorter arm of the molecule consists of one phenyl ring and 4-n-alkyloxy terminal chains whereas the long arm of the molecule possesses containing two phenyl rings which are linked via imine linkage and reactive 4-n-undecenyloxy as a terminal chain. The thermal stabilities of the newly synthesised compounds were carried out by thermogravimetric analysis (TGA). The mesomorphic behaviour was investigated by polarising optical microscopy (POM) and differential scanning calorimetry (DSC). All the compounds exhibit enantiotropic nematic phase along with smectic phases (SmA and SmC phases). Interestingly, the compounds with lower 4-n-alkyloxy terminal chains (n = 4 and 6) exhibit a wide range of optically isotropic DC phase. On increasing, the terminal 4-n-alkoxy chain length the DC phase disappears. The photophysical properties of the compounds were investigated in different solvents and in the solid state. It was observed that the compound exhibit absorption in UV region and emission in the green region.