Wang Feifei, Jiang Lan, Pan Changji, Wang Zhipeng, Lian Yiling, Wang Qingsong, Tao Wenpan, Sun Jingya
Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China.
College of Control Science and Engineering, China University of Petroleum (East China), Qingdao 266580, China.
Nanophotonics. 2022 Oct 24;11(21):4727-4736. doi: 10.1515/nanoph-2022-0379. eCollection 2022 Dec.
Holograms hidden inside transparent materials are important for information encryption storage because of their advantages of secrecy, and could completely avoid information loss caused by surface wear. Inside the transparent material, the modified filaments array was need for hologram fabrication to change the optical phase or amplitude of incident laser, which is sensitive to the change of refractive index. Then the uniformity of modified filaments inside transparent materials is highly required. In this study, by tuning the interval time of the double-pulse processing, holograms with improved imaging quality were fabricated by double-pulse femtosecond laser and the effect and mechanism of self-trapped excitons (STEs) on the ablation have been systematically studied. The imaging quality of the hologram fabricated with double-pulse laser was superior to that of the one fabricated with the single-pulse laser and 350 fs was verified to be the best time interval for double-pulse processing. The evolution of the electrons dynamics was investigated by using the pump-probe technology. With the double-pulse time interval increasing, the residual electrons, excitons, STEs, and defects caused by the first sub-pulse would become dominated sequentially. The results demonstrated the controllability of STEs and quality improvement of final structures by double-pulse femtosecond laser processing.
隐藏在透明材料内部的全息图因其保密性优势，对于信息加密存储非常重要，并且能够完全避免因表面磨损导致的信息丢失。在透明材料内部，需要用改性细丝阵列来制作全息图，以改变入射激光的光学相位或幅度，而这对折射率的变化很敏感。因此，对透明材料内部改性细丝的均匀性有很高要求。在本研究中，通过调整双脉冲处理的间隔时间，利用双脉冲飞秒激光制作出了成像质量得到改善的全息图，并系统地研究了自陷激子（STE）对烧蚀的影响及机制。用双脉冲激光制作的全息图的成像质量优于用单脉冲激光制作的全息图，并且验证了350飞秒是双脉冲处理的最佳时间间隔。利用泵浦 - 探测技术研究了电子动力学的演化。随着双脉冲时间间隔的增加，由第一个子脉冲产生的残余电子、激子、STE和缺陷将依次占据主导地位。结果证明了通过双脉冲飞秒激光加工对STE的可控性以及最终结构质量的提高。
