Terahertz waves generally refer to electromagnetic waves in the frequency range of 0.1 to 10 THz, between microwave and infrared. Because THZ waves have good temporal and spatial coherence, low photon energy, large transmission capacity and strong penetration ability, THZ waves have irreplaceable scientific and application potential in the fields of precision spectroscopy, radar imaging, biomedicine, national defense security screening, communication sensing and so on.
Terahertz radiation source is the key to the development of terahertz science and technology. Traditional terahertz radiation sources usually have disadvantages such as expensive materials, large volume and complex system, and the ability to regulate optical parameters such as bandwidth and polarization of terahertz radiation pulses is very limited. Efficient, flexible and broadband terahertz generation and optical parameter regulation are an important research direction in terahertz science and technology. In recent years, a spin-optoelectronic terahertz radiation source based on a ferromagnetic/non-magnetic heavy metal heterostructure with nanometer thickness has attracted wide attention. The terahertz generation mechanism based on ferromagnetic/non-magnetic heterostructures is mainly due to the ultrafine inverse spin Hall effect, where the light-induced spin flow is replaced by a ultrafine charge flow, which radiates terahertz coherent pulses. Although its radiation intensity is comparable to that of millimeter-thick optical rectifier crystal, how to further improve the field intensity of terahertz radiation pulse and strengthen the regulation ability of terahertz radiation pulse remains to be studied.
Recently, the Terahertz Technology Innovation Institute led by Academician Zhuang Songlin of the School of Optoelectronics at the University of Shanghai for Science and Technology, in collaboration with scientists from Fudan University, Shanghai University, University of Wollongong, and University of Moscow, studied the Pt/CoFe/Ta ferromagnetic/non-magnetic heterostructure spin optoelectronics terahertz radiation source prepared on polyethylene terephthalate (PET) flexible substrate. It is found that the flexible terahertz radiation source has the advantages of high emission efficiency, good stability, low cost, adjustable polarization and flexible bending. Importantly, the researchers innovatively propose a cascade terahertz radiation source based on this flexible PET/Pt/CoFe/Ta ferromagnetic/non-magnetic heterostructure, which not only effectively improves the field intensity of the terahertz pulse radiation, but also can effectively regulate the time domain waveform of the terahertz pulse radiation by combining it with an ultra-structured surface. The results further show that the cascaded spin-optoelectronic terahertz radiation source is perfectly suitable for terahertz time-domain spectral analysis. The researchers believe that the cascaded flexible PET/STE can be used as a basic module, showing strong research and application value in the generation and regulation of terahertz radiation, and is expected to be integrated into future chat-scale, compact terahertz devices and spectral systems.
The study, titled "Cascaded Amplification and Manipulation of Terahertz Emission by Flexible Spintronic Heterostructures," Published in Laser & Photonics Reviews (Region 1).
This work was supported by the Science Center Project of the National Natural Science Foundation of China (61988102).
Article link:
Z. Jin, Y. Peng, Y. Ni, G. Wu, B. Ji, X. Wu, Z. Zhang, G. Ma, C. Zhang, L. Chen, A. V. Balakin, A. P. Shkurinov, Y. Zhu, S. Zhuang,Cascaded Amplification and Manipulation of Terahertz Emission by Flexible Spintronic Heterostructures, Laser Photonics Rev. 2100688 (2022) https://onlinelibrary.wiley.com/doi/full/10.1002/lpor.202100688
FIG. 1 Schematic diagram of terahertz radiation cascade amplification and its regulation based on flexible ferromagnetic/non-magnetic heterostructures
(Photo :Laser & Photonics Reviews website)
