Wang Sicong, Wei Chen, Feng Yuanhua, Cao Hongkun, Li Wenzhe, Cao Yaoyu, Guan Bai-Ou, Tsukamoto Arata, Kirilyuk Andrei, Kimel Alexey V, Li Xiangping
Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou, 510632, China.
Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
Light Sci Appl. 2021 Jan 6;10(1):8. doi: 10.1038/s41377-020-00451-z.
Although photonics presents the fastest and most energy-efficient method of data transfer, magnetism still offers the cheapest and most natural way to store data. The ultrafast and energy-efficient optical control of magnetism is presently a missing technological link that prevents us from reaching the next evolution in information processing. The discovery of all-optical magnetization reversal in GdFeCo with the help of 100 fs laser pulses has further aroused intense interest in this compelling problem. Although the applicability of this approach to high-speed data processing depends vitally on the maximum repetition rate of the switching, the latter remains virtually unknown. Here we experimentally unveil the ultimate frequency of repetitive all-optical magnetization reversal through time-resolved studies of the dual-shot magnetization dynamics in GdFeCo. Varying the intensities of the shots and the shot-to-shot separation, we reveal the conditions for ultrafast writing and the fastest possible restoration of magnetic bits. It is shown that although magnetic writing launched by the first shot is completed after 100 ps, a reliable rewriting of the bit by the second shot requires separating the shots by at least 300 ps. Using two shots partially overlapping in space and minimally separated by 300 ps, we demonstrate an approach for GHz magnetic writing that can be scaled down to sizes below the diffraction limit.
尽管光子学是数据传输最快且最节能的方法，但磁性仍然是存储数据最便宜且最自然的方式。目前，对磁性的超快且节能的光学控制是一个缺失的技术环节，这阻碍了我们实现信息处理的下一次演进。借助100飞秒激光脉冲在GdFeCo中发现全光磁化翻转，进一步引发了人们对这个引人关注的问题的浓厚兴趣。尽管这种方法在高速数据处理中的适用性至关重要地取决于开关的最大重复率，但后者实际上仍然未知。在此，我们通过对GdFeCo中双脉冲磁化动力学的时间分辨研究，实验揭示了重复全光磁化翻转的极限频率。通过改变脉冲强度和脉冲间间隔，我们揭示了超快写入和磁比特最快可能恢复的条件。结果表明，尽管第一次脉冲引发的磁写入在100皮秒后完成，但第二次脉冲对比特进行可靠重写需要脉冲间隔至少300皮秒。利用在空间上部分重叠且最小间隔为300皮秒的两个脉冲，我们展示了一种可扩展到低于衍射极限尺寸的吉赫兹磁写入方法。
