A terahertz near-field nanoscopy revealing edge fringes with a fast and highly sensitive quantum-well photodetector

• Published in: iScience 2022-07, Vol.25 (7), p.104637, Article 104637
• Main Authors: Qiu, Fucheng, You, Guanjun, Tan, Zhiyong, Wan, Wenjian, Wang, Chang, Liu, Xiao, Chen, Xinzhong, Liu, Rui, Tao, Hu, Fu, Zhanglong, Li, Hua, Cao, Juncheng
• Format: Article
• Language: English
• Subjects: Nanotechnology; Quantum physics; Radiation physics
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2022.104637

We demonstrate the successful implementation of a terahertz (THz) quantum-well photodetector (QWP) for effective signal collection in a scattering-type scanning near-field optical microscope (s-SNOM) system. The light source is an electrically pumped THz quantum cascade laser (QCL) at 4.2 THz, which spectrally matches with the peak photoresponse of THz QWP. The sensitive THz QWP has a low noise equivalent power (NEP) of about 1.1 pW/Hz0.5 and a spectral response range from 2 to 7 THz. The fast-responding capability of the THz QWP is vital for detecting the rapidly tip-modulated THz light which can effectively suppress the background noise. The THz images of the nanostructure demonstrate a spatial resolution of about 95 nm, corresponding to ∼λ/752 at 4.2 THz. We experimentally investigate and theoretically interpret the formation of the fringes which appear at the edge position of a gold stripe in the THz near-field image. [Display omitted] •THz scattering-type scanning near-field optical microscope with a high-power THz QCL•Highly sensitive THz quantum-well photodetector for effective signal collection•Nanoscale spatial resolution reveals local optical properties in THz range•Experimentally investigate and theoretically interpret the formation of the edge fringes Radiation physics; Nanotechnology; Quantum physics