共查询到20条相似文献,搜索用时 31 毫秒
1.
Xiaoxia Zhong Xiuqin Yu Qu Li Shouyu Luo Yingli Chen Yu Sui Jie Yin 《Optics Communications》2001,190(1-6):333-337
The alignment of azobenzene molecules in DR19-PUI film induced by all-optical poling is identified. When the writing beams of frequencies ω and 2ω are both linearly polarized with their polarization directions parallel to each other, azobenzene molecules tend to reorient to perpendicular direction (i.e. direction perpendicular to the polarization of writing beams). At the end of the writing process more molecules orient in perpendicular direction than those in parallel direction (i.e. direction parallel to the polarization of writing beams). The alignment of molecules in parallel or perpendicular direction is, respectively, characteristic of noncentrosymmetry or centrosymmetry. It is the alignment of molecules in parallel direction that results in the second-order nonlinearity in the poled film. 相似文献
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Method of improving optical poling efficiency in polymer films 总被引:2,自引:0,他引:2
The alignment of dye molecules in optically poled polymer films is modeled. We point out that when writing beams (fundamental and second harmonic) are linearly polarized with their polarization directions parallel, the majority of the dye molecules in a poled film are axially oriented perpendicular to the writing-beam polarization, whereas the minority are polar oriented parallel to the writing-beam polarization. Only the latter, however, contribute to the second-order nonlinearity of the film. This model is verified by experiments. Based on the model, a new method of improving optical poling efficiency is put forward. 相似文献
3.
在聚合物表面刻写方格子的新方法及理论研究 总被引:1,自引:0,他引:1
为了提高制作偶氮苯微结构的实验技术,在偶氮苯聚合物的光致异构和光致取向特性的基础上,利用两激光束的新实验方案,运用比较简便的分步制作的方法,成功的在偶氮苯功能化聚合物薄膜表面“刻写”出二维的正方格子结构。提出了一个新的光异构取向场理论:在两束偏振方向互相垂直的偏振光照射下,偶氮苯聚合物表面光栅的形成是光异构取向场的干涉的结果,并对实验现象进行了解释。用计算机对实验结果进行了模拟,将模拟结果与实验结果进行了比较,结果表明计算机模拟将会更加有利于偶氮苯聚合物微结构的设计和制作。 相似文献
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Using the all-optical poling method, we observed the formation of a surface-relief grating (SRG) in an amorphous polymer film containing azo dye molecules in side chain positions. The experiment consists of a seeding-type process. We used a recently described experimental setup that permits a periodic nonlinear pattern to be produced by the index dispersion of glass. The particular configuration permits photoinduced translation diffusion of the azo chromophores to be observed as the origin of the SRG formation. Analyses of the gratings recorded by use of s (TE) and p (TM) polarization of the writing beams are conducted by atomic-force microscopy. The effect is attributed to mass transport from regions of high isomerization activity to regions of lower activity. 相似文献
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制备了以分散橙25为客体的掺杂型有机聚合物PMMA薄膜样品,对之进行了全光极化研究,极化使薄膜产生诱导二阶非线性光学效应,种子光的强度越大,其二阶非线性极化率达到的饱和值越大;种子光的位相差、相对强度比、光场强度等因素影响薄膜的二阶非线性的优劣. 相似文献
10.
C. Wang H. Fei J. Xia Y. Yang Z. Wei Q. Yang G. Sun 《Applied physics. B, Lasers and optics》1999,68(6):1117-1120
We report on optically controlled image storage based on photo-induced alignment in azobenzene liquid-crystalline polymer
films. Measurements reveal that the polymer film possesses photo-induced birefringence of large magnitude and the characteristic
of long-term optical storage. The photo-induced alignment process is used for storing images. The stored image is read from
the film placed between two crossed polarizers. It is demonstrated clearly that the alignment of the azo chromophores as well
as the stored image can be easily controlled by choosing the appropriate polarization of the irradiating light or by rotating
the film.
Received: 20 October 1998 / Revised version: 7 December 1998 / Published online: 31 March 1999 相似文献
11.
偶氮苯侧链液晶聚合物薄膜中图象存储的光学控制 总被引:4,自引:1,他引:3
基于偶氯苯聚合物液晶的光控双折射实现了图象存储的光学控制,所用聚合物液晶薄膜具有大的光致双折射和长久光学存储特性。利用光控分子取向进行图象存储,存储的图象从介于两正交偏振片间的样品薄膜读出。实验清楚地表明通过改变照射光的偏振方向或旋转样品可很容易地控制输出图象的亮度和取向。 相似文献
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为探索不同的极化条件对分子取向的影响,用旋涂法制备了偶氮主客体掺杂薄膜,并用电晕极化的方法分别在不同温度和厚度条件下使分子取向,通过测量极化前后紫外-可见吸收谱,研究了平均取向因子的变化,并和二次谐波产生结果进行了比较。实验结果表明:对于厚度相同的偶氮薄膜,随着温度的升高,平均取向因子增大,但二次谐波信号强度先增大后减小;温度越接近聚合物玻璃转变温度,分子越容易取向,但温度过高,聚甲基丙烯酸甲酯变为粘滞态,部分偶氮分子容易在高温下蒸发掉,导致二次谐波信号强度降低,而平均取向因子增大;随着薄膜厚度的增大,针-板电极电场造成薄膜内部电场分布的不均匀性增加,极化效率降低,平均取向因子不断减小,二次谐波信号强度先增大后减小。 相似文献
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利用激光拉曼散射技术,对剪切作用下受限于钢球与石英盘之间的纳米级液晶5 CB的分子排列取向进行研究. 结果表明,在特定的实验条件下,可以得到高信噪比的纳米级润滑膜的拉曼散射信号(20∶1). 同时发现,当激光偏振方向与剪切运动方向平行(垂直)时,所得拉曼信号强度达到最大(小)值,表明纳米级液晶5 CB分子在剪切诱导作用下,沿剪切运动方向趋于定向排列. 另外,当钢球与石英盘之间的剪切速度逐渐增大时,受限的纳米级液晶5 CB的拉曼信号强度也逐渐增大. 最后,利用根据相对光强干涉原理研制的纳米膜厚测量仪对纳米级
关键词:
薄膜润滑
分子排列取向
拉曼散射 相似文献
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Polarization holographic recording was investigated in a liquid-crystalline azobenzene side-chain polymer. A highly stable
polarization holographic grating with the diffraction efficiency of 12.6% was written in the polymer film by two orthogonally
linearly polarized 532 nm beams with equal intensities of 150 mW/cm2. The polarization grating was studied with a 633 nm probe beam by surveying the conversion of the polarization state of the
probe beam and measuring the dependence of diffraction efficiency on the polarization direction of the probe beam. It was
found that the ± first-order diffraction efficiency and the polarization of the diffracted wave depended strongly on the polarization
of the readout wave. The unusual diffraction properties of the recorded grating were attributed to the presence of the circular
photoinduced birefringence.
PACS 42.40.Ht; 42.40.Lx; 78.20.Fm 相似文献
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Two different procedures for the preparation of bimorph structures within nonlinear optical polymer layers are reported. One technique consists of thermally assisted poling above the glass-transition temperature followed by photo-induced poling below the glass-transition temperature. In this poling scheme, the second step is based on the photoisomerization of the dipole molecules. The other method comprises two consecutive thermally assisted poling steps with opposite field polarity in a double layer of two nonlinear optical polymers with different glass-transition temperatures. Pyroelectric thermal analysis is employed for analyzing the stability of the resulting bimorph structures, while pyroelectric depth profiling allows for a non-destructive qualitative analysis of their polarization distributions. 相似文献
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Ramanujam PS 《Optics letters》2003,28(23):2375-2377
I demonstrate high-resolution polarization holographic recording with evanescent waves in a thin film of an azobenzene polyester deposited directly on the hypotenuse of a highly refractive prism. A spatial frequency greater than 7000 lines/mm and diffraction efficiency greater than 1% have been achieved. It was found that diffraction efficiency increases in the dark after the writing beams have been switched off. The biphotonic effect found in other azobenzene polymers, which converts cis states of the azobenzene to trans states followed by an ordering process that is due to aggregation, is proposed as the reason for this increase in diffraction efficiency. 相似文献
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Permanent light-induced polar orientation via all-optical poling and photothermal cross-linking in a polymer thin film 总被引:1,自引:0,他引:1
A. Apostoluk J.-M. Nunzi V. Boucher A. Essahlaoui R. Seveno H.W. Gundel C. Monnereau E. Blart F. Odobel 《Optics Communications》2006,260(2):708-711
An epoxy-based crosslinkable polymer functionalized with nonlinear optical (NLO) photochromic dye known as Red Acid Magly was polarly oriented via thermally-assisted all-optical poling to enhance the photostability of the induced order. During the writing (seeding) process the film was cross-linked by heating with a hot-plate and irradiated simultaneously by the coherent superposition of the 1.06 μm fundamental and 0.532 μm second harmonic beams of a nanosecond pulsed Nd:YAG laser. We demonstrate that crosslinking between the polymer matrix and the pendant chromophore groups induced during the thermally-assisted all-optical poling procedure results in a stable light-induced second order susceptibility. 相似文献
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The paper presents the second-order optical nonlinearities from χ(2) gratings induced by holographic all-optical poling for azobenzene polymer. Second harmonic (SH) signal along the directions with two different vectors was measured. One is strong SH signal diffracted in the same direction as 2ω writing beam with wave vector k2ω and the other is weak SH signal diffracted in the direction of wave vector of 4kω - k2ω + Δk where kω is wave vector of ω beam and Δk is the wave vector mismatch whose vector is parallel to kω. The latter signal was used as a tool to monitor the formation of holographic χ(2) gratings in real-time because it has off-axis wave vector different from both kω and k2ω. The increase of 2ω intensity on poling process led to the large increase of second-order optical nonlinearity. The real-time monitoring showed that it also gave the large relaxation of second-order optical nonlinearity on poling process. The increase of 2ω (532 nm) energy enhanced the increase of local heating, which led to easier alignment of azobenzene chromophore and also larger relaxation of aligned chromophore. 相似文献
20.
Zaporojtchenko Vladimir Pakula Christina Basuki Sri Wahyuni Strunskus Thomas Zargarani Dordaneh Herges Rainer Faupel Franz 《Applied Physics A: Materials Science & Processing》2011,102(2):421-427
Fully reversible light-induced switching of the capacitance with changes larger than 50% has been achieved by using photo-active
thin polymer films. The films consist of PMMA polymer blended with high concentrations of branched azobenzene ether dye molecules.
Polymer thin sheet capacitors can be easily produced by spin coating and drop casting in various thicknesses ranging from
100 nm to 8 μm, respectively. Reversible capacitance switching is induced by illumination with UV and visible light, respectively.
The capacitance change is correlated to the trans to cis isomerization of the azobenzene ether molecules and the alignment of the molecular dipoles in the film. Switching times depend
on chromophore concentration, film thickness and light intensity used. The influence of wavelength of the light, of the temperature
as well as of an electrical field applied during illumination on the capacitance change is addressed. 相似文献