Near-field THz nanoscopy with novel accelerator-based photon sources

Sep 10, 2019, 11:10 AM
Keynote Keynote talk


Lukas M. Eng (Institute of Applied Physics, School of Science, TU Dresden, 01062 Dresden, Germany)


This talk advertises scattering-type scanning near-field infrared nanospectroscopy (s-SNIM) in the spectral range of 75 to 1.2 THz [1,2], as provided by the free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany. By combining s-SNIM with FELBE, we demonstrate a -independent optical resolution of ~10 nm only, by exploring structured Au samples, Graphene-nanotransistors, meta-materials [3,4], and local-scale ferroic phase-transitions [5 - 7] down to LHe temperatures [8]. Moreover, also the non-linear optical responses at IR wavelengths can be explored as recently demonstrated when inspecting highly-doped GaAs/InGaAs core/shell nanowires [9]. Our THz-s-SNIM was also integrated into a THz pump-probe setup for the local analysis of excited states in structured SiGe samples. We developed a sophisticated demodulation technique that extracts pump-induced signals with a superior signal-to-noise ratio [10]. In addition, HZDR recently extended the available wave¬length ranges down to the 100 GHz radiation, employing the novel super-radiant TELBE light source [11,12]. We adapted our s-SNIM to that novel TELBE photon source as well, achieving an equally high spatial resolution as with FELBE. This allows now to bridge the famous THz-gap in order to explore novel quantum phenomena of magnons, spins, and phonon polaritons.
[1] F. Kuschewski et al., Appl. Phys. Lett. 108, 113102 (2016).
[2] S.C. Kehr et al., Synch. Rad. News 30, 31 (2017).
[3] S.C. Kehr et al., ACS Photonics 3, 20 (2016).
[4] M. Fehrenbacher et al., Nano Lett. 15, 1057 (2015).
[5] J. Döring et al., J. Appl. Phys. 120, 084103 (2016).
[6] J. Döring, LME, et al., Appl. Phys. Lett. 105 , 053109 (2014).
[7] A. Butykai, LME, et al., Sci. Rep. 7, 44663 (2017).
[8] D. Lang, LME, et al., Rev. Sci. Instrum. 89, 033702 (2018).
[9] D. Lang, LME, et al., Nanotechnology 30, 084003 (2019).
[10] F. Kuschewski, LME, et al., Sci. Rep. 5, 12582 (2015).
[11] B. Green et al., Sci. Rep. 6, 22256 (2016).
[12] S. Kovalev et al., Struct. Dyn. 4, 024301 (2017).

Topic 14. Applications and interdisciplinary subjects

Primary author

Lukas M. Eng (Institute of Applied Physics, School of Science, TU Dresden, 01062 Dresden, Germany)

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