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Proceedings Paper

A terahertz confocal microscope for far-field thermal radiation detection and near-field sub-wavelength imaging
Author(s): Qianchun Weng; Le Yang; Jie Xu; Qingbai Qian; Haochi Yu; Bo Zhang; Zhenghua An; Ziqiang Zhu; Wei Lu
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Paper Abstract

We present a novel scattering-type scanning near-field optical microscope (s-SNOM) operating in the terahertz (THz) wavelength. A home-made ultra-high sensitive detector named charge sensitive infrared phototransistor (CSIP, detection wavelength ~15 μm) is equipped for spontaneous thermal radiation detection (external illumination should be avoided). Thermal emission from room-temperature objects is collected by a cassegrain objective lens placed above the sample, and focused to a pinhole (d=250 μm) which is kept in liquid-helium (LHe) temperature(4.2 K). With the background radiation from environment efficiently blocked by the low-temperature pinhole, the detector is only sensitive to the THz radiation from a small spot (~λ) on sample surface (the confocal point). As a result, thermal radiation spontaneously emitted by object itself is measured with an excellent spatial resolution of ~14 μm (diffraction-limit). For overcoming the diffraction limit by detecting the near-field evanescent waves, this THz microscope is combined with a home-built atomic-force microscope (AFM). With sharp AFM tip (<100 nm) scattering the evanescent waves with an improved tip-modulation method, we successfully obtained thermal near-field images with a spatial resolution of ~100 nm, which is already less than 1% of the detection wavelength (15 μm). This THz s-SNOM should be a powerful tool for various material research down to the nanometer scale.

Paper Details

Date Published: 5 November 2015
PDF: 6 pages
Proc. SPIE 9795, Selected Papers of the Photoelectronic Technology Committee Conferences held June–July 2015, 97950U (5 November 2015); doi: 10.1117/12.2212029
Show Author Affiliations
Qianchun Weng, East China Normal Univ. (China)
Shanghai Institute of Technical Physics (China)
Le Yang, Fudan Univ. (China)
Jie Xu, Fudan Univ. (China)
Qingbai Qian, Fudan Univ. (China)
Haochi Yu, Fudan Univ. (China)
Bo Zhang, Shanghai Institute of Technical Physics (China)
Zhenghua An, Fudan Univ. (China)
Ziqiang Zhu, East China Normal Univ. (China)
Wei Lu, Shanghai Institute of Technical Physics (China)

Published in SPIE Proceedings Vol. 9795:
Selected Papers of the Photoelectronic Technology Committee Conferences held June–July 2015
Shenggang Liu; Songlin Zhuang; Michael I. Petelin; Libin Xiang, Editor(s)

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