Anisotropic hydroxypropylcellulose films as alignment layers of a bistable ferroelectric device

Hydroxypropylcellulose films are used as the alignment substrate in a liquid crystal bistable electro-optical device. These alignment films were characterized by atomic force microscopy. The electro-optical behaviour of this device, which operates in the Clark-Lagerwall mode, is identical to that observed for typical SSFLC cells. In particular the bistability of the cell was clearly observed, the threshold voltage was measured and an estimation of the anchoring energy of the LC mixture used, in this type of system, was made.     

The recurrence relations for the spheroidal functions

The integrable properties of the spheroidal equations are investigated. The shape-invariance property is proved to be retained for the spheroidal equations, for which the recurrence relations are obtained. This is the extension of the recurrence relation of the Legendre polynomials.     

基于导波驱动相变材料超构表面的基波及二次谐波聚焦

利用超构表面优异的波前调控能力将片上光子集成电路对光场的操控拓展至自由空间是当前一项重要课题.本文采用传输相位方法设计了一种基于波导模式激发的内嵌式超构表面,其相位分布同时满足导模的基频以及二倍频的聚焦.在此基础上,将内嵌式材料限定为相变材料,结合其在不同相态时的折射率差异,通过仿真手段实现了两种相态下分别针对于基波和二次谐波的聚焦.在基波(或二次谐波)实现高质量聚焦时,焦点处二次谐波(或基波)的成分得到了很大程度上的抑制,更有利于后续完全滤波.进一步地,通过在波导层底面嵌入与顶面完全相同的超构表面,并横向错开半个周期,最终将关于基波聚焦和二次谐波聚焦的器件效率提升为原先单阵列情形的2.2倍和3.7倍.本文的研究为导波驱动(或激发)超构表面的线性及非线性多功能复合调控提供了一种新的可能途径.     

Nonadiabatic effects in the molecular high-order harmonic generation from two-center molecular ions

The nonadiabatic effects in the molecular high-order harmonic generation (MHHG) from H₂⁺ and its isotope have been theoretically investigated beyond the Born-Oppenheimer approximations. It is found that (i) due to the asymmetric contributions of the harmonic emission on the rising and the falling parts of the laser field, the frequency red-shifts in the MHHG can be found. As the initial vibrational state or the pulse intensity increases, the red-shifts of the harmonics are decreased and even the blue-shifts of the harmonics can be found in the higher pulse intensity with the higher vibrational state. With the increase of the pulse duration, the frequency red-shifts and the blue-shifts in the MHHG are decreased and enhanced, respectively. The shifts of the harmonics from the heavy nuclei are decreased compared with those from the light nuclei. (ii) Due to the coupling of the electron-nuclear dynamics, the non-odd harmonics can be produced at the larger internuclear distance. With the increase of the initial vibrational state or the pulse duration, the generations of the non-odd harmonics can be enhanced. As the pulse intensity increases, the intensities of the non-odd harmonics are first increased and then decreased at the much larger pulse intensity. Due to the slower nuclear motion, the generations of the non-odd harmonics are decreased as the nuclear mass increases. (iii) With the increase of the alignment angle of the molecule ions, the nonadiabatic effects in MHHG (including the shifts of the harmonics and the generations of the non-odd harmonics) are decreased.     

HeH2+分子谐波辐射的空间分布

理论研究了HeH2+分子发射高次谐波的空间分布情况。结果表明：分子谐波发射主要集中在He核和H核附近。当核间距离较小时,He核辐射谐波强度要比H核辐射谐波强度高2~3个数量级。当核间距离较大时,He核辐射谐波强度要比H核辐射谐波强度高4~5个数量级。当空间非均匀激光场引入后,谐波截止能量得到延伸,并且,随着空间非均匀激光场位置由负向到正向移动(-100 a.u.到100 a.u.),谐波截止得到进一步延伸。但是He核辐射谐波强度依然大于H核。最后,通过叠加谐波可获得脉宽在60 as的超短脉冲。     

核运动对非奇次谐波产生的影响

理论研究了H2+、D2+、T2+辐射高次谐波的特点.结果表明,在核运动影响下,不仅奇次谐波呈现红移现象,而且谐波光谱呈现非奇次谐波.随着核质量增大,奇次谐波频移和非几次谐波强度都减弱.但是随着激脉宽增大,非奇次谐波的产生明显被增强.理论分析表明,谐波频移是由谐波辐射在激光上升和下降区间的非对称性导致的;非奇次谐波是由于分子对称性在较大核间距离处遭破坏产生的.