Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 93: Plasmonics & Nanooptics VI: Near-Field Microscopy and Phenomena

O 93.5: Vortrag

Freitag, 5. April 2019, 11:30–11:45, H8

Polarization-dependent resonant near-field spectroscopy in the mid- to far-infrared regime — •Lukas Wehmeier¹, Tobias Nörenberg¹, Denny Lang², Susanne C. Kehr¹, and Lukas M. Eng¹ — ¹Technische Universität Dresden, Germany — ²Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Germany

Resonant infrared (IR) near-field spectroscopy provides a highly material-specific response with sub-wavelength spatial resolution of ∼10 nm. Here, we provide the infrared near-field response of selected paraelectric and ferroelectric materials (i.e. SrTiO₃, LiNbO₃, and BiFeO₃) that we investigated via scattering scanning near-field optical microscopy (s-SNOM), using the mid- to far-infrared free-electron laser (FEL) at HZDR. For these materials, we demonstrate that resonant near-field excitation is possible for both s- and p-polarized incident IR beams, which is particularly interesting for the nanoscopic investigation of anisotropic materials. We explored, for instance, the different near-field resonances of BiFeO₃, finding characteristic s-SNOM enhancement for three consecutive phonon modes in the 10 to 60 µm wavelength range. Utilizing the same material, we present the first realization of a superlens within the so-called THz gap, demonstrating a fascinating application of sub-wavelength imaging capabilities.