Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 42: Posters Magnetism I

MA 42.34: Poster

Wednesday, March 18, 2020, 15:00–18:00, P3

Super-resolution in THz-spectral imaging — •Tristan Winkel¹, Finn-Frederik Lietzow¹, Yuta Sasaki², Nina Meyer¹, Jana Kredl¹, Tobias Tubandt¹, Christian Denker¹, Jakob Walowski¹, Shigemi Mizukami², and Markus Münzenberg¹ — ¹Institut für Physik, Universität Greifswald, Greifswald, Germany — ²Advanced Institute for Materials Research, Tohoku University, Sendai, Japan

THz spectroscopy is attractive for scientific research, especially life science [1]. Its wavelength of several hundred µ m usually limits its spatial resolution by diffraction. Super-resolution imaging techniques would be required to overcome this limit, while near-field imaging is probably the most feasible.

We investigate THz pulses by excitation of CoFeB/Pt layer stacks [2] and commercial Auston switch emitters with fs laser pulses. 2D motor-stages and LT-GaAs Auston switch detectors combined with Fourier transformation allow for spatially resolved THz spectroscopy.

The spatial resolution using the commercial emitter with focusing optics is half the wavelength. A drastic increase in spatial resolution appears using near-field imaging. A gold test pattern on the spintronic emitter leads to a spatial resolution of less than a tenth of the wavelength. The observation of FWHM of about 10 µ m at 1 THz while having FHWM of 3 µ m for the corresponding laser excitation using the "knife-edge method" demonstrates the high potential of our approach.

[1] S. K. Mathanker et al., ASABE 56 (2013).

[2] T. Seifert, Nature Photon, 10, pp. 483−488 (2016).