GaP波导型发射器产生频率可调谐太赫兹脉冲

报道了利用脉宽可调的光子晶体光纤飞秒激光放大器抽运矩形波导结构的GaP晶体太赫兹(THz) 发射器产生频率可调谐的超快THz脉冲.非线性晶体中光整流过程产生的THz辐射频率随抽运光脉冲宽度而 变化. GaP波导THz发射器可通过波导的几何尺寸来控制色散,以达到增加有效作用长度和提高输出功率的目的. 不同横截面尺寸的波导型发射器的THz辐射峰值频率随相位匹配条件的改变而改变,加以脉宽调节技术, 可以在大频谱范围获得频谱精细可调的THz脉冲.实验中在1 mm×0.7 mm的波导型THz发射器中获得了 频率可调谐的THz脉冲.提出实现THz辐射频率大范围调谐的GaP波导型阵列发射器的实施方案.     

Fast calibration methods using cosmic rays for a neutron detection array

An overall irradiation and calibration technique was introduced and applied to a test scintillation detector array. An integral conversion method was used to reduce the nonlinearity of the time difference spectrum, and to improve the position determination especially for positions close to the two ends of a long scintillation bar. An overall position resolution of about 3.0 cm (FWHM) was extracted from the residual analysis method and verified by a direct measurement. Energy calibration was also realized by selecting cosmic rays at different incident angles. The bulk light attenuation lengths for the four test bars were also determined. It is demonstrated that these methods are especially efficient for calibrating large and complex detector arrays.     

波段外激光辐照光导型InSb探测器的一种新现象

利用不同功率密度的10.6 μm(光子能量为0.12 eV)连续激光辐照了禁带宽度为0.228 eV的光导型锑化铟探测器, 得到了与以往报道不同的实验现象. 当10.6 μm波段外激光辐照光导型探测器时, 探测器吸收激光能量后温度升高. 在探测器的温升过程中, 存在一个转变温度T₀. 当探测器的温度T<T₀时, 载流子浓度基本不变, 迁移率随温度的升高呈T^-2.35趋势下降, 引起探测器的电导率减小, 电阻增大, 响应输出电压升高; 当T>T₀时, 热激发载流子浓度随温度的升高呈指数增长, 电阻急剧下降, 超过了载流子迁移率降低对电阻的影响, 响应输出急剧下降. 光电导探测器在较高功率密度波段外激光辐照下的响应特性是载流子的浓度和迁移率在温度影响下相互作用的结果. 这对进一步完善半导体内载流子输运模型提供了实验依据.     

从乌龟坐标在动态Vaidya黑洞上的推广谈起

从一类参数未定的一般形式的乌龟坐标变换出发, 找出了在动态Vaidya黑洞背景下能将波动方程化为标准形式且无发散的乌龟坐标所满足的条件. 结果表明, 以乌龟坐标变换为主要特征的Damour-Ruffini方法, 用来计算动态黑洞的Hawking辐射时, 只适用于事件视界, 无法应用于表观视界.     

基于光子晶体光纤的高纯度量子关联光子对的制备

使用脉冲光在室温下抽运一根长1 m 的高非线性光子晶体光纤, 产生了中心波长分别位于830 nm 和1411 nm的具有量子关联性的闲频与信号光子. 实验中闲频和信号通道的带宽分别是15 nm和35 nm. 对单通道光子计数率的拟合结果显示光子几乎全部来源于光纤中的自发四波混频过程, 未受到Raman散射噪声的影响. 当闲频和信号通道的光子产生率约为每脉冲0.0085个时, 测得符合计数率与随机符合计数率的比值为102, 接近理论极限, 不仅证明了光子对的低噪声性, 而且表明所产生的光子对本身具有窄带频谱特性, 因而实验中对其收集效率很高. 此外, 这种高纯度关联光子对还联接了不同波段, 在量子信息技术中有着潜在的应用.     

靶向新药吉非替尼的核磁共振波谱研究

应用1D、2D NMR实验技术（¹H NMR、¹³C NMR、DEPT、¹H-¹H COSY、¹H-¹³C HMQC、¹H-¹³C HMBC等）研究了靶向新药吉非替尼的结构,对其1H NMR和¹³C NMR谱峰作了全归属,并讨论了F原子对吉非替尼的¹H、¹³C NMR的影响.     

Reflection chromaticity of cholesteric liquid crystals with sandwiched periodical isotropic defect layers

We study one-dimensional photonic crystals made of cholesteric liquid crystals with sandwiched isotropic defect layers. Based on the Berreman Fast 4 × 4 matrix method, the dispersion relation of one-dimensional photonic crystals is calculated and the corresponding reflection chromaticity is obtained. It is found that the color shift could be controlled by adjusting the thickness and refractive index of the isotropic defect layers. Compared with conventional structures, the reflection chromaticity of this structure is insensitive to the incident angle, if the thickness ratio of the cholesteric liquid crystals to that of the isotropic defect layers and the refractive index of periodical isotropic defect layers are properly set. Furthermore, the common forbidden bands for both left and right circular polarizations can be obtained, and we also take the wavelength-dependent refractive indices into consideration and obtain the reflected light chromaticity with the incident angle increasing. The proposed device can be used as a reflective color filter in the display industry.