Terahertz (THz, 1011~1013 Hz) related technology, with its superior spectral performance, has wide application potential in communication, security, sensing fields and so on. Its engineering applications highly depend on a variety of THz components.
Recently, a collaborated team from Hefei Institutes of physical science (HFIPS), Chinese Academy of Sciences (CAS) and University of Science and Technology (USTC) successfully developed a highly efficient magneto-tunable and phonon-based monochromatic THz generator with a frequency of ~0.9 THz by utilizing a 2D ferromagnetic Cr2Ge2Te6 crystal.
"Benefiting from the bosonic nature of the radiation mechanism, this new THz source has advantages of "zero threshold", high quality factor and radiation efficiency,” said Prof. SHENG Zhigao from Hight Magnetic Field Laboratory, HFIPS.
In this research, combining the theoretical and experimental approaches, the joint research team selected the 2D van der Waals magnetic semiconductor Cr2Ge2Te6 crystal and innovatively exploited the excellent properties of its van der Waals interlayered breathing phonon mode (boson) with the THz-TDS magneto-optic system. They found the breathing mode could effectively couple with incident co-frequency THz pulse and form a new quasi-bosonic particle, namely phonon-polariton. This quasi-bosonic particle could then generate far-field electro-magnetic radiation with monochromatic frequency comparable to the phonon mode.
With the strong spin lattice coupling existing in this 2D material, researchers tried to regulate the radiation via the spin-phonon interaction channel. They found that the phonon-related THz radiation could also be effectively modulated by external magnetic fields.
The successful development of this phonon-related monochromatic THz source not only gives people better understanding about phonon-polaritons in low-dimensional magnetic materials, but also provides a novel strategy for the realization of new THz sources.
The results are published in Advanced Science.
Schematic of the van der Waals phonon-polariton based monochromatic THz radiation. (Image by CHENG Long)