Effects of intermodal dispersion on short pulse propagation in multi-core fibers

The effects of intermodal dispersion on ultrashort optical pulse propagation through multi-core fibers are analyzed theoretically, which has been ignored in previous studies. A three-core fiber with collinear and triangular configuration and a four-core fiber are considered. We demonstrate with numerical examples that the intermodal dispersion can cause pulse breakup effect in multi-core fibers.     

Femtosecond laser-induced microstructure in Foturan glass

We report on the microstructure formation in Foturan glass, induced by 1~kHz, 120 femtosecond laser irradiation. It is found that the line-shaped filamentation, not void array tends to be formed in this glass. This is different from our previous experimental results in fused silica and BK7 glasses. A possible mechanism Ag$^+$ captures the free electrons generated by laser, is proposed to explain the observed phenomena.     

非简并双光子Jaynes-Cummings模型中贝尔非定域性的演化

基于赝自旋算符的关联所对应的贝尔算符期待值,研究了各种双模非经典态(纠缠相干态、对相干态以及双模压缩真空态)在非简并双光子Jaynes-Cummings模型中贝尔非定域性的动力学特性.结果表明:对于纠缠相干态,贝尔非定域性的演化与双模场平均光子数的大小息息相关;对于对相干态和双模压缩真空态,贝尔非定域性会在有限的时间内完全消失,之后又基本上复原到初始值,呈现出周期性振荡现象.     

Real-time surface profile measurement using a feedback type of sinusoidal phase modulating interferometer

In this paper, we propose a sinusoidal phase modulating (SPM) interferometer that is insensitive to external disturbances, and its measuring principle is analyzed theoretically. In the SPM interferometer, the interference signal is detected by a high-speed image sensor based on a low-speed CCD and a signal processing circuit is used to obtain the phase of each point on the surface. Therefore, the surface profile can be measured real-time. The experiments measuring the surface profile of a wedge-shaped optical flat show that the measurement time of the SPM interferometer is less than 10 ms, the repetitive measurement accuracy is 4.2 nm. The results show that the impacts of nonlinear distortion of the piezoelectric transducer (PZT) and part external disturbance are removed.     

Optical and mechanical properties of AlF3 films produced by pulse magnetron sputtering of Al targets with CF4/O2 gas

In this study, AlF₃ thin films were deposited by pulse magnetron sputtering of Al targets with different ratios of CF₄/O₂ gas and at different sputtering powers. The optical and mechanical properties of the AlF₃ thin films were analyzed. The transmittance spectra showed no obvious negative inhomogeneous refractive indices. Denser films with a low optical absorption were obtained when high sputtering powers were used (larger than 30 W). The lowest extinction coefficient (7.3 × 10⁻⁴ at 193 nm) of the films can be reached with 12 sccm O₂ flow rate and at 160W sputtering power. All of the residual stresses were compressive and their trends were consistent with the refractive indices. The lowest compressive stress (0.068 GPa) was obtained when the AlF₃ films were prepared at 160W sputtering power.     

LPCVD法制备的高纯半绝缘4H-SiC晶体ESR谱特性

利用电子自旋共振波谱（ESR）仪,分析由低压化学气相沉积（LPCVD）法制备的高纯半绝缘4H-SiC材料本征缺陷.结果发现,在暗场条件下获得的缺陷信息具有碳空位（V_C）及其络合物的特征;谱线具有半高宽较大、峰谷明显不对称的特点.分析认为造成ESR谱线半高宽较大及峰谷不对称现象的主要原因是测试温度较高.同时,吸收谱中峰谷不对称现象及较大半高宽现象的出现还与不对称的晶格结构及缺陷浓度的不均匀分布有关.在110 K测试温度下,能级上的电子分布对ESR谱特性影响很小. 关键词： 低压化学气相沉积 高纯半绝缘4H-SiC 电子自旋共振 本征缺陷     

Spectral Characterization of Couplings in a Mixed Optomechanical Model *

Abstract:We study the spectrum of single-photon emission and scattering in a mixed optomechanical model which consists of both linear and quadratic optomechanical interactions. The spectra are calculated based on the exact long-time solutions of the single-photon emission and scattering processes in this system. We find that there exist some phonon sideband peaks in the spectra and there are some sub peaks around the phonon sideband peaks under proper parameter conditions. The correspondence between the spectral features and the optomechanical interactions is confirmed, and the optomechanical coupling strengths can be inferred by analyzing the resonance peaks and dips in the spectra.     

A new graphical coding of DNA sequence and its similarity calculation

The DNA primary sequence is translated into “structure graph” based on classification of its four bases. Then the invariants, such as topological indices, are extracted from those graphic representations of DNA primary sequences, and used to calculate the similarities among the eleven species. From these similarities/dissimilarities the homologies can be revealed that they are in agreement with evolutionary relation satisfactorily.     

Collective dynamics in fully hydrated phospholipid bilayers studied by inelastic x-ray scattering

The short wavelength density fluctuation of DLPC (dilaurylphosphatidylcholine) bilayers close to full hydration has been studied by the inelastic x-ray scattering technique below and above the main transition temperature. The analysis based on a generalized three effective eigenmode theory allows us to construct the dispersion relation of the high frequency sound mode for the first time. The marked softening of the excitation near k = 14 nm(-1), corresponding to the lipid chain-chain correlation peak in the structure factor, in the L(alpha) phase implies prevalent occurrences of short-wavelength in-plane motions of lipid chains that might be of importance for transportation of small molecules across membranes.