Hu Xuehao, Kinet Damien, Mégret Patrice, Caucheteur Christophe
Opt Lett. 2016 Jul 1;41(13):2930-3. doi: 10.1364/OL.41.002930.
Bragg gratings are photo-inscribed in trans-4-stilbenemethanol doped PMMA fibers using a 325 nm He-Cd laser and a phase mask. Two distinct behaviors are reported depending on the laser power density. In the high-density regime with 637 mW/mm, the grating reflectivity is stable over time after the writing process, but the reflected spectrum is of limited quality, as the grating length is limited to the laser width (1.2 mm). The beam is then enlarged to 6 mm, decreasing the power density to 127 mW/mm. In this case, the grating reflectivity strongly decays after the writing process. A fortunate property here results from the recovery of the initial reflectivity using a post-inscription thermal annealing. Both behaviors are attributed to the evolution between trans- and cis-isomers.
使用325 nm氦镉激光器和相位掩模，在反式-4-苯乙烯甲醇掺杂的聚甲基丙烯酸甲酯（PMMA）光纤中光写入布拉格光栅。根据激光功率密度报告了两种不同的行为。在功率密度为637 mW/mm的高密度状态下，写入过程后光栅反射率随时间稳定，但反射光谱质量有限，因为光栅长度限于激光宽度（1.2 mm）。然后将光束扩大到6 mm，将功率密度降低到127 mW/mm。在这种情况下，写入过程后光栅反射率强烈衰减。幸运的是，通过写入后热退火可以恢复初始反射率。这两种行为都归因于反式和顺式异构体之间的转变。
