Bragg-type polarization gratings formed in thick polymer films containing azobenzene and tolane moieties
Bragg-type polarization gratings formed in thick polymer films containing azobenzene and tolane moieties
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DOI：
10.1021/la061587j
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发表时间：
2007-01-02
期刊：
影响因子：
3.9
通讯作者：
Ikeda, Tomiki
中科院分区：
文献类型：
--
作者：
Ishiguro, Makoto;Sato, Daisuke;Ikeda, Tomiki
在布拉格区，在含有偶氮苯和二苯乙炔（甲苯）的厚聚合物薄膜上形成全息光栅。合成了含有不同含量的具有光敏性的偶氮苯和侧链上具有大双折射的甲苯的非晶态聚合物，制备了光学透明的厚聚合物薄膜。用Ar+激光（488 nm）的线偏振光照射膜，测量He-Ne激光（633 nm）通过一对交叉偏振片（膜之间）的透射率，以估计光致双折射（Delta n）。随着聚合物膜中甲苯部分含量的增加，n的值也随之增加。当两个线偏振光束在488 nm处干涉薄膜时，观察到衍射光束，最大衍射效率（eta）随着甲苯部分含量的增加而增加。在含有70 mol%的甲苯部分的薄膜中，eta最高可达99%，并且明显观察到布拉格衍射引起的角选择性。我们认为，即使聚合物没有显示出液晶相，偶氮苯部分的排列变化也会引起甲苯部分的协同分子运动。当两个正交的圆偏振光束干涉薄膜时，形成布拉格型偏振光栅。在920ms内eta值达到90%。
Holographic gratings were formed in thick polymer films containing azobenzene and diphenylacetylene (tolane) moieties in the Bragg regime. Amorphous polymers containing various contents of the azobenzene moiety with photosensitivity and the tolane moiety with large birefringence in the side chain were synthesized, and optically transparent thick polymer films were prepared. The films were irradiated with a linearly polarized beam from an Ar+ laser (488 nm), and the transmittance of a He-Ne laser beam (633 nm) through a pair of crossed polarizers, with the film between them, was measured to estimate a photoinduced birefringence (Delta n). The value of Delta n increased with an increase in the tolane moiety content in the polymer films. When two linearly polarized beams at 488 nm were interfered in the film, a diffraction beam was observed, and the maximum diffraction efficiency (eta) increased with the tolane moiety content. In the film containing 70 mol% of the tolane moiety, the highest eta of 99% was achieved, and angular selectivity due to Bragg diffraction was clearly observed. We consider the cooperative molecular motion of the tolane moieties to be induced by the photoinduced change in alignment of the azobenzene moieties even if the polymers show no liquid-crystalline phase. When two orthogonal circularly polarized beams were allowed to interfere in the film, a Bragg-type polarization grating was formed. It was found that the value of eta reached 90% within 920 ms.