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At terahertz (THz) frequencies, scattering-type scanning near-field optical microscopy (s-SNOM) based on continuous wave sources mostly relies on cryogenic and bulky detectors, which represents a major constraint for its practical application. Here, we devise a THz s-SNOM system that provides both amplitude and phase contrast and achieves nanoscale (60-70nm) in-plane spatial resolution. It features a quantum cascade laser that simultaneously emits THz frequency light and senses the backscattered optical field through a voltage modulation induced inherently through the self-mixing technique. We demonstrate its performance by probing a phonon-polariton-resonant CsBr crystal and doped black phosphorus flakes.
Optical Society of America
Publication date: 
9 Jul 2018

Maria C Giordano, Stefan Mastel, Clemens Liewald, Lorenzo L Columbo, Massimo Brambilla, Leonardo Viti, Antonio Politano, Kai Zhang, Lianhe Li, A Giles Davies, Edmund H Linfield, Rainer Hillenbrand, Fritz Keilmann, Gaetano Scamarcio, Miriam S Vitiello

Biblio References: 
Volume: 26 Issue: 14 Pages: 18423-18435
Optics express