2-μm emission performance of Tm~(3+)-Ho~(3+) co-doped tellurite glasses

The emission properties of 2-μm region fluorescence of Tm~(3+)-Ho~(3+) co-doped tellurite glasses are investigated. Introducing F~- ions to the composition of tellurite glasses plays a positive effect on the 2-μm emission.A maximum intensity of 2-μm emission is achieved when 1.5-mol%Tm_2O_3 and l-mol% Ho_2_O3 concentration are doped in the glasses.The emission cross section and gain coefficient of the ~5I_8→~5I_7 transition of Ho~(3+) are calculated.The emission cross section has a maximum of 1.29×10~(-2...     

Detection system for singlet oxygen luminescence in photodynamic therapy

Singlet oxygen （^1O2） is widely considered to play a major role in photodynamic therapy （PDT）, and thus an increasing attention has been focused on the direct detection of ^1O2 near-infrared luminescence around 1270 nm for PDT dosimetry. A new sensitive detection system is developed to directly measure the temporal and spectral resolved ^1O2 luminescence spectra. The triplet state and ^1O2 lifetimes of Rose Bengal as a model photosensitizer in different solvents are determined, and the obtained results agree well with the published data. Our detection system has the potential application in ^1O2 luminescence-based PDT dosimetry.     

Pupil design based on Fisher information optimization to extend field depth in practical optical system

<正>Wavefront coding(WFC) is used to extend the field depth of an incoherent optical system by employing a phase mask on the pupil.We uses a Fisher information(FI) metric based optimization method to design a phase mask by taking the modulation transfer function(MTF) of the practical optical system into consideration. This method can modulate the wavefront so that the point spread function and optical transfer function are insensitive to the object distance.The simulation results show that the optimized phase mask based on the proposed method can further improve the defocusing image quality while maintaining the focusing image quality.     

Artificial neural network method for determining optical properties from double-integrating-spheres measurements

<正>Accurate measurement of the optical properties of biological tissue is very important for optical diagnosis and therapeutics.An artificial neural network(ANN)-based inverse reconstruction method is introduced to determine the optical properties of turbid media,which is based on the reflectance(R) and transmittance (T) of a thin sample measured by a double-integrating-spheres system.The accuracy and robustness of the method has been validated,and the results show that the root mean square errors(RMSEs) of the absorption coefficientμ_a and scattering coefficientμ'_s reconstruction are less than 0.01 cm~(-1) and 0.02 cm~(-1),respectively.The algorithm is not only very accurate in the case of a lower albedo(~0.33),but also very robust to the noise of R and T especially for theμ'_s reconstruction.     

Effects of annealing on luminescence efficiency of large-size YAG:Ce crystal grown by temperature gradient techniques

<正>YAG:Ce crystal with a diameter of 110 mm is successfully grown by the temperature gradient technique (TGT).The effects of annealing on the luminescence efficiency of YAG:Ce crystal are investigated,and the optimal annealing temperature and atmosphere are obtained.The mechanism of variation behavior of the luminescence efficiency of YAG:Ce under different annealing conditions is discussed and some details on the luminescence associated with color centers are analyzed.     

Numerical simulations of the impact of wavefront phase distortions of pump on the beam quality of OPA

<正>A numerical model of optical parametric amplification(OPA) is introduced to investigate the impact of wavefront phase distortion of pump on the beam quality of signal.Numerical results show that the unidentical walk-off directions of the pump and the idler waves are the main factors leading to the transfer of wavefront phase distortions of the pump to the signal,and by reducing the angle between the two directions,the beam quality factor(M~2) can be greatly decreased and hence the good beam quality of the signal can be maintained.     

The role of refocusing in dynamic X-wave formation during femtosecond laser filamentation in water

<正>With the evolution of a laser pulse in water,the formation of a nonlinear X wave during femtosecond filamentation is investigated based on numerical simulations.In particular,we analyze the far-field angularly resolved spectra obtained for different temporal portions of the ultrashort pulse during its propagation. Our result shows that the refocusing of ultrashort pulse leads to the formation of dynamic X wave which essentially manifests itself as conical emission.     

约瑟夫森结(阵列)与谐振器的耦合效应研究

利用一种新的电路模型系统研究了约瑟夫森结(阵列)与谐振器的耦合效应.以结的电压自锁定台阶幅度ΔI为目标值,得到了谐振电路的电阻R、谐振频率fr对耦合的影响规律,并给出了合理解释;以结阵列的相位互锁定强度IL为目标,研究了IL对锁定电压VL的依赖关系,同时,通过相关计算将其与通常电路模型下得到的结果进行了比较.     

温度对应变式位移传感系统灵敏系数的影响

应变式位移传感系统的工作原理是基于电阻应变效应,该系统具有精度高﹑稳定性好等优点,但温度尤其是极端低温环境将影响该系统的灵敏系数,进而影响其测量精度.本文介绍了一种可用于低温环境的应变式位移传感系统,理论分析和实验研究了温度对该系统灵敏系数的影响,研究结果为其在低温环境中的应用提供了一定基础。     

T型量子点结构中的自旋极化输运过程

我们利用单杂质Anderson模型及运动方程等理论,通过求解格林函数的方法研究了通过T型量子点结构(耦合于铁磁电极和介观环量子点结构)的自旋极化输运过程.研究结果表明,与量子点相耦合的铁磁电极中的极化强度是控制量子点电子输运的重要参数,由此可以达到自旋阀效应.另外我们还发现与量子点相耦合的介观环中的磁通会影响电子自旋向上和自旋向下近藤共振峰的分裂程度,但若加入适当的外磁场,那么这样的分裂将被抵消。