Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards Nanoellipsometry
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 l...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-09-01
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| Series: | Applied Sciences |
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| Online Access: | https://www.mdpi.com/2076-3417/13/18/10429 |
| _version_ | 1797581408190857216 |
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| author | Felix G. Kaps Susanne C. Kehr Lukas M. Eng |
| author_facet | Felix G. Kaps Susanne C. Kehr Lukas M. Eng |
| author_sort | Felix G. Kaps |
| collection | DOAJ |
| description | 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 CO<sub>2</sub> 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. |
| first_indexed | 2024-03-10T23:04:45Z |
| format | Article |
| id | doaj.art-ece576cb2b914fc093a0c135f1bb218d |
| institution | Directory Open Access Journal |
| issn | 2076-3417 |
| language | English |
| last_indexed | 2024-03-10T23:04:45Z |
| publishDate | 2023-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Applied Sciences |
| spelling | doaj.art-ece576cb2b914fc093a0c135f1bb218d2023-11-19T09:27:36ZengMDPI AGApplied Sciences2076-34172023-09-0113181042910.3390/app131810429Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards NanoellipsometryFelix G. Kaps0Susanne C. Kehr1Lukas M. Eng2Institute of Applied Physics, TUD Dresden University of Technology, 01062 Dresden, GermanyInstitute of Applied Physics, TUD Dresden University of Technology, 01062 Dresden, GermanyInstitute of Applied Physics, TUD Dresden University of Technology, 01062 Dresden, GermanyElectric 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 CO<sub>2</sub> 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.https://www.mdpi.com/2076-3417/13/18/10429nanoopticsmaterials sciencenanotechnologynanoellipsometrys-polarizationp-polarization |
| spellingShingle | Felix G. Kaps Susanne C. Kehr Lukas M. Eng Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards Nanoellipsometry Applied Sciences nanooptics materials science nanotechnology nanoellipsometry s-polarization p-polarization |
| title | Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards Nanoellipsometry |
| title_full | Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards Nanoellipsometry |
| title_fullStr | Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards Nanoellipsometry |
| title_full_unstemmed | Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards Nanoellipsometry |
| title_short | Polarization Sensitivity in Scattering-Type Scanning Near-Field Optical Microscopy—Towards Nanoellipsometry |
| title_sort | polarization sensitivity in scattering type scanning near field optical microscopy towards nanoellipsometry |
| topic | nanooptics materials science nanotechnology nanoellipsometry s-polarization p-polarization |
| url | https://www.mdpi.com/2076-3417/13/18/10429 |
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