Anna Rumyantseva

Nano-patterning photosensitive polymers using local field enhancement at the end of apertureless SNOM tips.

We show experimentally that local optical field enhancement can occur at the end of an apertureless SNOM tip illuminated by an external light source. Our approach consists in the use of a photosensitive polymer, placed in the tip near‐field, to record intensity distribution in the vicinity of the tip end. The excited nanometre‐size light source permits us to produce nano‐patterns on the polymer surface which are then characterized by atomic force microscopy. Experimental images show the influence, on the field enhancement, of three important experimental parameters: the polarization state of the incident light, the geometry of the external illumination and the radius of curvature of the tip apex. These results are shown to be in good agreement with two‐dimensional numerical calculations based on the finite‐difference time‐domain method. We show preliminary nanometre‐size patterns created by this nano‐source excited at a metallic tip extremity and discuss the potential of this approach for near‐field optical lithography.

Near-field optical imaging with a nanotip grown on fibered polymer microlens

Pointed carbon nanotips have been deposited on polymer microlensed optical fibers and used as highly resolving scattering nanoprobes. Optical characterizations supported by simulations demonstrate an efficient spatial filtering where the light scattered by the carbon tip is selectively coupled into the fiber core. As an application, a channel surface waveguide was characterized in collection mode. A special attention was given to the polarization response, and the s-polarized field is found to be slightly favored due to the detection direction. The proposed hybrid probe’s robustness, the symmetric detection and design flexibility it offers, makes it an attractive tool for nano-optics.

Light propagation mapping in surface waveguides using nano carbon probe grown on polymer tipped optical fiber

We report on the fabrication, simulation and use of carbon nano-probes grown on the apex of polymer-tipped optical fibers. The carbon needles are used as near-field scattering probes to image light propagation in surface waveguides. The scattered light is selectively and efficiently coupled in the supporting optical fiber through the polymeric structure which is used here as a submicronic collection optics. This combination leads to high spatial resolution and high detection efficiency.

ZnO top-down structuring for UV photonic applications(Conference Presentation)

ZnO is a promising II-VI semiconductor for UV applications although p-type ZnO is not yet available. Nevertheless it remains an alternative material for GaN and its alloy InGaN. For example, the exciton binding energy of ZnO (60 meV) is higher than that of GaN (21 meV). This allows ZnO to emit light at ambient temperature and interestingly, it increases the device brightness. Besides promising intrinsic properties, light-matter control and especially in the UV relies on the ability of material nanostructuring. We present here two different kinds of top-down process in order to nanostructure ZnO. The first one relies on Electron Beam Lithography (EBL) combined with a lift-off process and inductively coupled plasma (ICP) reactive ion etching (RIE). Nickel (Ni) has been used as a mask in order to have a high selectivity in the presence of C2F6 and O2 ionized gases. The etching rate used was 26nm/s in order to avoid roughness. The second process is called Direct Holographic Patterning (DHP). ZnO thin films have been holographicaly patterned for the first time by direct photodissolution in NaCl solution using laser interference lithography. Application of an electrical potential strongly increases the dissolution rate and decreases the pattern formation time. Both processes will be discussed in terms of their respective potential for light confinement in the UV.

Coupling between a sub-wavelength optical cavity and a plasmonic nanostructure probed by SERS

We report on the utilization of optical sub-wavelength quasi Fabry-Perot cavity coupled with the Raman microscopy to study the interaction between the localized surface plasmon resonance of gold nanoparticles and the surface plasmon resonance of a gold film. We show an enhancement of the Fabry-Perot oscillations when the distance between nanoparticle and gold film decrease.

Mapping of localized surface plasmon fields via exposure of a photosensitive polymer

We present a method for mapping the electromagnetic field distribution in the vicinity of noble metal nanoparticles able to sustain localised surface plasmon resonance (LSPR). The field distribution is coded by topographic change in a self-developing photosensitive polymer (PMMA-DR1). Metallic nanostructures are fabricated by e-beam lithography and optically characterised by extinction spectroscopy. Photoinduced topographic changes are checked by means of atomic force microscopy (AFM). The dipolar character of the surface modification around the particles agrees qualitatively with theoretical predictions and a strong correlation between LSPR position and the relief depth is found.