Nanochemistry in the near-field of an optical fiber tip

Laser material processing is a widely used technique for materials shaping and localized starting of a chemical reactions, e.g., for cornea correction or laser-marking. The minimal achievable resolution is given by optical diffraction limit of about half of the wavelength of the light. I.e., at a wavelength of 500 nm (green light) the resolution is limited to about 250 nm. The limitation is not valid any more in the near-field of an optical light source at distances of only a few nanometers. This effect is employed for scanning near-field optical microscopes (SNOMs), which have a much better resolution than conventional microscopes. Here as light-source an optical fiber tip is approached to a surface. In the present project we want to combine chemical laser processing and SNOM technique for realization of laser-induced chemical reactions on a nanoscale. The chemical reactions shall be confined to an area with a diameter of less than 10 nanometers. By scanning (inherent to the SNOM technique) we will produce three dimensional nanopatterns into substrates employing etching or deposition reactions. We will study the dependence of the pattern formation on the tip geometry as well as on laser parameters like polarization, wavelength and pulse-width of the laser-light. This will allow us to estimate the local light intensity distribution at various tip-sample distances and to compare these results with model calculations. Finally, we will produce prototype three-dimensional (3D) patterned samples for potential technical applications. This could be special nanofeatures in semiconductors suitable for quantum-dots, nanostructures in superconducting films used as frequency filters in telecommunication, 3D-nanopatterns in polymers for photonic crystals or regular noble metal nanodots as model catalysts.

Laser material processing is a widely used technique for materials shaping and localized starting of a chemical reactions, e.g., for cornea correction or laser-marking. The minimal achievable resolution is given by optical diffraction limit of about half of the wavelength of the light. I.e., at a wavelength of 500 nm (green light) the resolution is limited to about 250 nm. The limitation is not valid any more in the near-field of an optical light source at distances of only a few nanometers. This effect is employed for scanning near-field optical microscopes (SNOMs), which have a much better resolution than conventional microscopes. Here as light-source an optical fiber tip is approached to a surface. In the present project we want to combine chemical laser processing and SNOM technique for realization of laser-induced chemical reactions on a nanoscale. The chemical reactions shall be confined to an area with a diameter of less than 10 nanometers. By scanning (inherent to the SNOM technique) we will produce three dimensional nanopatterns into substrates employing etching or deposition reactions. We will study the dependence of the pattern formation on the tip geometry as well as on laser parameters like polarization, wavelength and pulse-width of the laser-light. This will allow us to estimate the local light intensity distribution at various tip-sample distances and to compare these results with model calculations. Finally, we will produce prototype three-dimensional (3D) patterned samples for potential technical applications. This could be special nanofeatures in semiconductors suitable for quantum-dots, nanostructures in superconducting films used as frequency filters in telecommunication, 3D-nanopatterns in polymers for photonic crystals or regular noble metal nanodots as model catalysts.