%0 Journal Article %1 Kaps_2023 %A Kaps, Felix G. %A Kehr, Susanne C. %A Eng, Lukas M. %D 2023 %I MDPI AG %J Appl. Sci. %K a %N 18 %P 10429 %R 10.3390/app131810429 %T Polarization sensitivity in scattering-type scanning near-field optical microscopy — towards nanoellipsometry %U https://doi.org/10.3390%2Fapp131810429 %V 13 %X Electric field enhancement mediated through sharp tips in scattering-type scanning near-field optical microscopy (s-SNOM) enables optical material analysis down to the 10-nm length scale and even below. Nevertheless, the out-of-plane electric field component is primarily considered here due to the lightning rod effect of the elongated s-SNOM tip being orders of magnitude stronger than any in-plane field component. Nonetheless, the fundamental understanding of resonantly excited near-field coupled systems clearly allows us to take profit from all vectorial components, especially from the in-plane ones. In this paper, we theoretically and experimentally explore how the linear polarization control of both near-field illumination and detection can constructively be implemented to (non-)resonantly couple to selected sample permittivity tensor components, e.g., explicitly to the in-plane directions as well. When applying the point-dipole model, we show that resonantly excited samples respond with a strong near-field signal to all linear polarization angles. We then experimentally investigate the polarization-dependent responses for both non-resonant (Au) and phonon-resonant (3C-SiC) sample excitations at a 10.6 µm and 10.7 µm incident wavelength using a tabletop CO2 laser. Varying the illumination polarization angle thus allows one to quantitatively compare the scattered near-field signatures for the two wavelengths. Finally, we compare our experimental data to simulation results and thus gain a fundamental understanding of the polarization’s influence on the near-field interaction. As a result, the near-field components parallel and perpendicular to the sample surface can be easily disentangled and quantified through their polarization signatures, connecting them directly to the sample’s local permittivity.

@article{Kaps_2023, abstract = {Electric field enhancement mediated through sharp tips in scattering-type scanning near-field optical microscopy (s-SNOM) enables optical material analysis down to the 10-nm length scale and even below. Nevertheless, the out-of-plane electric field component is primarily considered here due to the lightning rod effect of the elongated s-SNOM tip being orders of magnitude stronger than any in-plane field component. Nonetheless, the fundamental understanding of resonantly excited near-field coupled systems clearly allows us to take profit from all vectorial components, especially from the in-plane ones. In this paper, we theoretically and experimentally explore how the linear polarization control of both near-field illumination and detection can constructively be implemented to (non-)resonantly couple to selected sample permittivity tensor components, e.g., explicitly to the in-plane directions as well. When applying the point-dipole model, we show that resonantly excited samples respond with a strong near-field signal to all linear polarization angles. We then experimentally investigate the polarization-dependent responses for both non-resonant (Au) and phonon-resonant (3C-SiC) sample excitations at a 10.6 µm and 10.7 µm incident wavelength using a tabletop CO2 laser. Varying the illumination polarization angle thus allows one to quantitatively compare the scattered near-field signatures for the two wavelengths. Finally, we compare our experimental data to simulation results and thus gain a fundamental understanding of the polarization’s influence on the near-field interaction. As a result, the near-field components parallel and perpendicular to the sample surface can be easily disentangled and quantified through their polarization signatures, connecting them directly to the sample’s local permittivity.}, added-at = {2023-10-17T09:38:49.000+0200}, author = {Kaps, Felix G. and Kehr, Susanne C. and Eng, Lukas M.}, biburl = {https://www.bibsonomy.org/bibtex/29e92934f09a586f3ed021fbb58e5c053/ctqmat}, day = 18, description = {Applied Sciences | Free Full-Text | Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards Nanoellipsometry}, doi = {10.3390/app131810429}, interhash = {35fec9b4ab6e9fcfea47624c9bb5f0eb}, intrahash = {9e92934f09a586f3ed021fbb58e5c053}, journal = {Appl. Sci.}, keywords = {a}, month = {09}, number = 18, pages = 10429, publisher = {{MDPI} {AG}}, timestamp = {2023-10-31T11:02:29.000+0100}, title = {Polarization sensitivity in scattering-type scanning near-field optical microscopy — towards nanoellipsometry}, url = {https://doi.org/10.3390%2Fapp131810429}, volume = 13, year = 2023 }