Near-field nanoscopy with infrared-to-THz accelerator-based photon sources

We advertise scattering-type scanning near-field infrared nanoscopy (s-SNIM) in the spectral range of 75 to 1.3 THz [1], using the narrow-band free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany [2], for illumination (see Fig. 1). When combining s-SNIM with FELBE, we demonstrate the wavelength-independent optical resolution of a few 10 nm only, by exploring structured Au samples [1], meta-materials [3,4], nanowires [5], minerals [6] and ferroic phase-transitions [7,8] down to LHe temperatures [7-9]. Notably, the intense radiation pulses from FELBE enable investigations of non-linear effects and optically excited samples on the nanometer scale [5]. Moreover, HZDR recently extended the wavelength range down to 100 GHz radiation employing the novel super-radiant TELBE light source [10,11]. We are adapting our s-SNIM to this TELBE photon source as well, aiming for equally high spatial resolution as with FELBE. The unique combination of infrared-to-THz spectroscopy and microscopy with a resolution of a few 10 nm enables near-field probing of polaritons based on plasmons, phonons, cooper pairs, and magnons, which dominate the materials’ optical response in this frequency regime and with that enable the fundamental characterization of light-matter interaction down to nanometer and molecular length scales.

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