Near-field THz nanoscopy at novel accelerator-based photon sources (Conference Presentation)

This talk advertises scattering-type scanning near-field infrared micro-spectroscopy (s-SNIM) in the spectral range of 75 to 1.3 THz [1], as provided by the free-electron laser FELBE, the narrow-band laser-light source at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany. We demonstrate the -independent s-SNIM resolution of a few 10 nm by exploring structured Au samples, Graphene-transistors, meta-materials [2], and local ferroelectric phase-transitions down to LHe [3]. s-SNIM secondly was integrated into a THz pump-probe experiment for the inspection of excited states in structured SiGe samples. We developed a novel demodulation technique with high temporal resolution [4] hence achieving an excellent Signal-to-Noise Ratio. Thirdly using the super-radiant TELBE light source [5], HZDR recently extended the wavelength range down to 100 GHz radiation. We adapted our s-SNIM to this TELBE photon-source as well, achieving an equally high spatial resolution as with FELBE. Moreover, the superb 30-fs temporal resolution of TELBE will allow us to study a multitude of physical phenomena with sub-cycle resolution [5,6], such as spin-structures, magnons and phonon polaritons. [1] F. Kuschewski et al., Appl. Phys. Lett. 108 (2016) 113102. [2] S.C. Kehr et al., ACS Photonics 3 (2016) 20. [3] J. Doring et al., Appl. Phys. Lett. 105 (2014) 053109. [4] F. Kuschewski et al., Sci. Rep. 5 (2015) 12582. [5] B. Green et al., Sci. Rep. 6 (2016) 22256. [6] S. Kovalev et al., Struct. Dyn. 4 (2017) 024301.