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Proceedings Paper

Coherent control of femtosecond spin current and terahertz wave generation in ferromagnetic heterostructures
Author(s): Xiaojun Wu; Bo Wang; Meng Xiao; Tianxiao Nie; Deyin Kong; Chandan Pandey; Yang Gao; Lianggong Wen; Weisheng Zhao; Cunjun Ruan ; Jungang Miao; Li Wang; Yutong Li
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Paper Abstract

Femtosecond control of electron spin not only promises the capability of satisfying the ever-increasing demand of storage information and ultrafast manipulation of magnetization in mediums, but also delivering controllable, highlyefficient, cost-effective and compact terahertz sources. Femtosecond spin dynamics have been extensively investigated these years with the methods of ultrafast magnetic-optical Kerr effect, inverse Faraday effect, inverse spin Hall effect and so on. Recently emerged coherent terahertz emission spectroscopy can also be employed to study this ultrafast spin dynamics with its unique advantages. For example, terahertz emission spectroscopy is a coherent, time-resolved, contactless Ampere-meter, which can be used to deduce the spin-charge conversion. However, femtosecond laser interaction with magnetic mediums is a rather complex process, there are still lots of physical mechanisms waiting to be unveiled. Here, we systematically investigate the femtosecond spin dynamics in ferromagnetic materials via polarization-resolved terahertz emission spectroscopy. We obtain detectable electromagnetic field radiation with its polarization parallel to the external magnetic field direction, which was not observed in the same materials in previous work. Inverse spin-orbit torque tilting is responsible for the observed phenomenon. Based on this mechanism, the efficiency and polarization of the generated terahertz waves can be coherently controlled and manipulated not only by the external magnetic fields, but also by the sample structures and the pumping femtosecond laser pulses. Our work not only helps further deepen understanding of the physical mechanism of all-optical magnetization reversal, boosting future spin recording technology, but also offers a very promising way for developing novel and efficient terahertz functional sources and devices.

Paper Details

Date Published: 5 November 2018
PDF: 7 pages
Proc. SPIE 10814, Optoelectronic Devices and Integration VII, 108140X (5 November 2018); doi: 10.1117/12.2504050
Show Author Affiliations
Xiaojun Wu, Beihang Univ. (China)
Bo Wang, Institute of Physics (China)
Univ. of Chinese Academy of Sciences (China)
Meng Xiao, Beihang Univ. (China)
Tianxiao Nie, Beihang Univ. (China)
Deyin Kong, Beihang Univ. (China)
Chandan Pandey, Beihang Univ. (China)
Yang Gao, Beihang Univ. (China)
Lianggong Wen, Beihang Univ. (China)
Weisheng Zhao, Beihang Univ. (China)
Cunjun Ruan , Beihang Univ. (China)
Jungang Miao, Beihang Univ. (China)
Li Wang, Institute of Physics (China)
Yutong Li, Institute of Physics (China)
Univ. of Chinese Academy of Sciences (China)
Shanghai Jiao Tong Univ. (China)

Published in SPIE Proceedings Vol. 10814:
Optoelectronic Devices and Integration VII
Xuping Zhang; Baojun Li; Changyuan Yu; Xinliang Zhang, Editor(s)

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