Xiaojun Wu of Beihang University leads a group of researchers actively seeking ways to understand, generate, and control THz radiation. According to Wu, terahertz (THz) waves have great potential for expanding real applications ranging from imaging to information encryption. However, the development of THz science and technology has been hindered by a lack of sufficiently efficient sources.
The research group led by Wu has been investigating a three-dimensional topological insulator of bismuth telluride (Bi2Te3) as a promising basis for an effective THz system. They recently systematically investigated THz radiation from Bi2Te3 nanofilms driven by femtosecond laser pulses. Their report published in Advanced Photonics demonstrates efficient generation of chiral THz waves with an arbitrarily adjustable polarization state that allows control of chirality, ellipticity, and principal axis.
According to Wu, bismuth telluride is a great candidate for future on-chip topological insulator-based terahertz systems. It has already exhibited excellent prospects in THz emission, detection, and modulation. The well-studied topological insulator presents a special spin-momentum locked surface state, which can also be accurately adjusted by various factors such as the number of atomic layers. Wu explains that this kind of THz source can efficiently radiate linearly and circularly polarized THz waves, with adjustable chirality and polarization. This will enable the development of THz science and applications in such areas as ultrafast THz opto-spintronics, polarization-based THz spectroscopy and imaging, THz biosensing, line-of-sight THz communications, and information encryption.