Matushiro Yu, Juodkazis Saulius, Hatanaka Koji, Watanabe Wataru
Opt Lett. 2017 Apr 15;42(8):1632-1635. doi: 10.1364/OL.42.001632.
Self-regeneration of volume gratings recorded inside polymethyl methacrylate (PMMA) after 70-100 days is demonstrated. First, volume gratings were made inside PMMA by femtosecond laser writing. The diffraction efficiency of the gratings reached the maximum-was regenerated-following an initial slow decrease within the first several days after the fabrication. Time-lapse measurements of the diffraction efficiency in both top-plane (as laser written) and side-plane illumination were used to monitor changes of the diffraction efficiency. The final efficiency was reaching values well in excess of the as-fabricated efficiencies, with a maximum diffraction efficiency of 90% for the side readout illumination. The regenerated volume grating is a possible candidate to achieve high diffraction efficiency in PMMA. The regeneration is consistent with the α-relaxation of the polymer structure and oxidation of the dangling bonds.
结果表明，聚甲基丙烯酸甲酯（PMMA）内部记录的体光栅在70-100天后能够自我再生。首先，通过飞秒激光写入在PMMA内部制作体光栅。光栅的衍射效率在制作后的最初几天内先缓慢下降，随后达到最大值并实现再生。通过对顶面（如激光写入面）和侧面照明下衍射效率的延时测量来监测衍射效率的变化。最终效率远超过制作时的效率，侧面读出照明的最大衍射效率达到90%。再生的体光栅有望在PMMA中实现高衍射效率。这种再生与聚合物结构的α弛豫和悬垂键的氧化相一致。
