Recently, the team of professor Min Hu of the University of Electronic Science and Technology of China (UESTC) terahertz research center collaborated with the team of professor Li Peining of Huazhong University of Science and Technology Optoelectronics National Laboratory to successfully develop the revolutionary “terahertz time-domain filtering nano-imaging technology (THz-TDF)”, and cooperated with the team of professor Zhang Hui of the School of Arts and Archaeology of Zhejiang University, Art and Archaeological Image Data Laboratory for the first time to apply it to the nanoscale spectral analysis of ancient painting pigments. The research results were published in an international high-level journal entitled “Time-domain-filtered terahertz nanoscopy of intrinsic light-matter interactions”Nano LettersThe University of Electronic Science and Technology of China (UESTC) is the first author of the paper, Professor Min Hu is the corresponding author, Professor Li Peining of Huazhong University of Science and Technology and Professor Zhang Hui of Zhejiang University are the co-corresponding authors, and the first author of the paper is the postdoctoral researcher Zhang Xiaoqiuyan of Min Hu’s team. The study used the terahertz nano-resolved near-field system independently developed by Chengdu Miji Technology Co., Ltd.
In recent years, terahertz (THz) technology has gained attention for its great potential in areas such as biosensing, security screening and information communication. Traditional far-field imaging techniques are subject to diffraction limits and cannot achieve sub-millimeter resolution. In response, near-field optical microscopy detects the optical properties of THz at the nanoscale by focusing incident THz waves to the nanoscale volume through the metallization tip. While THz wavelengths are longer, the resonant surface waves generated on the tip and cantilever mask the sample’s intrinsic near-field response and hinder its further development. In the process of solving the surface wave interference problem of traditional terahertz near-field imaging technology, Professor Min Hu’s team completed the development of innovative time-domain spectroscopy technology, combined with this time-domain spectral truncation technology, successfully solved the surface wave interference problem and achieved ultra-high resolution terahertz imaging.
Technological innovation: breakthrough in surface wave interference, providing high-resolution nano-spectroscopy
the terahertz wave covers the characteristic spectrum of several important materials and is widely used in the fields of materials science, life sciences and communications. The traditional terahertz nano-optical technology is often unable to accurately extract the intrinsic spectral characteristics due to probe surface wave interference. The research team pioneered the terahertz time-domain filtering nano-imaging technology, which successfully eliminated the interference caused by surface waves (simulation and experiment are shown in Figure 1). The accuracy and resolution of the terahertz nano-optical spectrum have been significantly improved.
Nanoscale Spectroscopic Reveal of Ancient Painted Pigments: Distinguishing Cinnabar from Lead Pill Pigments
Using this technology, the research team conducted an in-depth analysis of the pigment sample of a Ming Dynasty color plastic, successfully identified the nanoscale vibration characteristics of cinnabar (α-HgS) and lead pellet (Pb O) pigments, and revealed that only cinnabar had significant vibration resonance characteristics at a frequency of 1.125 THz. Cinnabar and lead pellet are commonly used paint pigments in ancient times, which may change color under the influence of external conditions, but their mechanism is still very controversial. The study is the first to achieve terahertz near-field spectroscopy imaging of ancient painted pigments, which helps to observe how these semiconductor pigments react under conditions such as illumination on a smaller scale, so as to more accurately grasp the pigment discoloration law and provide a scientific basis for the preventive protection of painted cultural relics. The technology achieves spatial resolution below 200 nm, and the nano-imaging results of ancient pigment samples are shown in Figure 2.
more applications for terahertz-TDF nano-imaging: optical studies of metal antennas
In addition, the team used terahertz-TDF nano-imaging technology to study the nano-optical properties of metal antennas. Experimental results show that the technology can clearly distinguish the resonance frequency changes of metal antennas of different lengths, and successfully reveal the dipole resonance mode of the antenna. Through the analysis of metal antennas with different lengths from 38 μm to 86 μm, the researchers found that the increase in antenna length leads to the phenomenon of redshift of resonant frequency, which is highly consistent with the numerical simulation results, demonstrating the potential of this technology in nanophotonics research (simulation and experimental results are shown in Figure 3).
Future prospects: promoting the development of terahertz nano-optical technology
In the future, smaller and more efficient nano-imaging systems are expected to be realized by integrating terahertz emission and detection technologies directly into the probe. This technology will provide strong support in the fields of quantum materials, nanophotonics and cultural relics protection, and promote the development of terahertz nano-optical technology to a wider range of application scenarios.
Link to the paper:https://doi.org/10.1021/acs.nanolett.4c03715
Group homepage:https://thz-sci.com/
Chengdu Miji Technology Co., Ltd.:https://www.mjthz.com/
Source: The University of Electronic Science and Technology of China (UESTC) View Original