Hybrid temperature effect on a quartz crystal microbalance resonator in aqueous solutions

The quartz crystal microbalance(QCM) is an important tool that can sense nanogram changes in mass. The hybrid temperature effect on a QCM resonator in aqueous solutions leads to unconvincing detection results. Control of the temperature effect is one of the keys when using the QCM for high precision measurements. Based on the Sauerbrey's and Kanazawa's theories, we proposed a method for enhancing the accuracy of the QCM measurement, which takes into account not only the thermal variations of viscosity and density but also the thermal behavior of the QCM resonator. We presented an improved Sauerbrey equation that can be used to effectively compensate the drift of the QCM resonator. These results will play a significant role when applying the QCM at the room temperature.     

Optical waveguide in Nd:Bi_(12)SiO_(20) crystal produced by multi-energy C ion implantation

We report the fabrication of a planar waveguide in the Nd:Bi_(12)SiO_(20) crystal by multi-energy C ions at room temperature. The waveguide is annealed at 200℃, 260℃, and 300℃ in succession each for 30 min in an open oven. The effective refractive index profiles at transverse electric(TE) polarization are stable after the annealing treatments. Damage distribution for multi-energy C ion implanted in Nd:Bi_(12)SiO_(20) crystal is calculated by SRIM 2010. The Raman and fluorescence spectra of the Nd:Bi_(12)SiO_(20) crystal are collected by an excitation beam at 633 nm and 473 nm, respectively. The results indicate the stabilization of the optical waveguide in Nd:Bi_(12)SiO_(20) crystal.     

Experimental design to measure the anchoring energy on substrate surface by using the alternating-current bridge

The anchoring property of the substrate surface of liquid crystal cells plays an important role in display and nondisplay fields. This property directly affects the deformation of liquid crystal molecules to change the phase difference through liquid crystal cells. In this paper, a test method based on the alternating-current bridge is proposed to determine the capacitance of liquid crystal cells and thus measure the anchoring energy of the substrate surface. The anchoring energy can be obtained by comparing the capacitance–voltage curves of twisted nematic liquid crystal cells with different anchoring properties in experimental and theoretical results simulated on the basis of Frank elastic theory. Compared with the other methods to determine the anchoring energy, our proposed method requires a simple treatment of liquid crystal cells and allows easy and high-accuracy measurements, thereby expanding the test ideas on the performance parameters of liquid crystal devices.     

A high-quality factor hybrid plasmonic nanocavity based on distributed Bragg reflectors

Herein,we propose a high-quality(Q) factor hybrid plasmonic nanocavity based on distributed Bragg reflectors(DBRs) with low propagation loss and extremely strong mode confinement.This hybrid plasmonic nanocavity is composed of a high-index cylindrical nanowire separated from a metal surface possessing shallow DBRs gratings by a sufficiently thin low-index dielectric layer.The hybrid plasmonic nanocavity possesses advantages such as a high Purcell factor(Fp) of up to nearly 20000 and a gain threshold approaching 266 cm~(-1)at 1550 nm,promising a greater potential in deep sub-wavelength lasing applications.     

An efficient continuous-wave YVO_4/Nd:YVO_4/YVO_4 self-Raman laser pumped by a wavelength-locked 878.9 nm laser diode

We report an efficient continuous-wave self-Raman laser at 1176 nm based on a 20-mm-long composite YVO_4/Nd:YVO_4/YVO_4 crystal and pumped by a wavelength-locked 878.9 nm diode laser.A maximum output power of 5.3 W is achieved at a pump power of 26 W,corresponding to an optical conversion efficiency of 20%and a slope efficiency of 21%.The Raman threshold for the diode pump power was only 0.92 W.The results reveal that in-band pumping by a wavelength-locked diode laser significantly enhances output power and efficiency of self-Raman lasers by virtue of improved pump absorption and relieved thermal loading.     

Tracking molecular structure deformation of nitrobenzene and its torsion-vibration coupling by intense pumping CARS

The structural deformation induced by intense laser field of liquid nitrobenzene(NB) molecule,a typical molecule with restricting internal rotation,is tracked by time- and frequency-resolved coherent anti-Stokes.Raman spectroscopy(CARS) technique with an intense pump laser.The CARS spectra of liquid NB show that the NO_2 torsional mode couples with the NO_2 symmetric stretching mode,and the NB molecule undergoes ultrafast structural deformation with a relaxation time of 265 fs.The frequency of NO_2 torsional mode in liquid NB(42 cm~(-1)) at room temperature is found from the sum and difference combination bands involving the NO_2 symmetric stretching mode and torsional mode in time- and frequency-resolved CARS spectra.     

杂质浓度对Zr替位掺杂γ-TiAl合金的结构延性和电子性质的影响

以Zr替代Ti(或Al)掺杂γ-TiAl体系为研究对象, 掺杂浓度(摩尔比)分别为1/54, 1/36, 1/24和1/16. 采用基于密度泛函理论的第一性原理方法, 计算研究了Zr掺杂γ-TiAl体系的晶体结构及其稳定性、延性和电子性质等. 结果显示, Zr替位掺杂, 可以改变γ-TiAl基合金的结构对称性. 计算的形成能表明, Zr替代Ti原子会使体系的形成能降低, 而Zr替代Al原子会使体系的形成能增加. 因而, 在掺入γ-TiAl时, Zr更倾向于替代Ti 原子, 但是Zr替代Al原子也具有一定的可能性, 从而会产生多样的掺杂体系, 对于改善合金的性质具有重要意义. 对各个体系轴比的计算与分析表明, 当掺杂浓度为1.85 at%–6.25 at% 时, Zr替代Al原子会使体系的轴比减小、接近于1, 从而改善合金的延性效果明显. 能带结构显示各个Zr掺杂γ-TiAl体系均具有金属导电性. 对电子态密度和布居数的分析表明, Zr替代Al原子后, Zr与其邻近Ti原子的共价键结合强度大为降低, 导致合金体系中的Ti-Al(Zr)键的平均强度明显减弱, 金属键增强, 这是改善γ-TiAl合金延性的重要因素.     

不同压电分流电路对声子晶体梁带隙的影响

通过在匀质基体梁上周期性对贴连有分流电路的压电片,可以形成一维声子晶体结构.不同分流电路将决定梁的带隙特性.电阻分流电路能够对梁的模态共振有一定的抑制作用,而且可以通过改变压电效应的强弱使Bragg带隙结构发生变化.LC分流电路会使梁产生局域共振带隙,其带隙是由压电片激励LC电路产生电磁振荡形成.引入电阻后会使LC电路的共振作用变弱,使得带隙衰减幅值变小,但可以扩宽带隙频率范围.