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

Fucheng Qiu; Guanjun You; Zhiyong Tan; Wenjian Wan; Chang Wang; Xiao Liu; Xinzhong Chen; Rui Liu; Hu Tao; Zhanglong Fu; Hua Li; Juncheng Cao

doi:10.1016/j.isci.2022.104637

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

iScience. 2022 Jun 18;25(7):104637. doi: 10.1016/j.isci.2022.104637. eCollection 2022 Jul 15.

Authors

Fucheng Qiu^{1

2}, Guanjun You³, Zhiyong Tan¹, Wenjian Wan¹, Chang Wang¹, Xiao Liu³, Xinzhong Chen⁴, Rui Liu⁵, Hu Tao⁶, Zhanglong Fu¹, Hua Li¹, Juncheng Cao¹

Affiliations

¹ Laboratory of Terahertz Solid-State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, and Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
² Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, and Chongqing School, University of Chinese Academy of Sciences, Chongqing 400714, China.
³ Shanghai Key Lab of Modern Optical Systems, Terahertz Technology Innovation Research Institute, and Engineering Research Center of Optical Instrument and System, Ministry of Education, University of Shanghai for Science and Technology, Shanghai 200093, China.
⁴ Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA.
⁵ Ithatron Instruments, Jiaxing 314006, China.
⁶ State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China.

Abstract

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/Hz^0.5 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.

Keywords: Nanotechnology; Quantum physics; Radiation physics.