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K Leosson

Publications and source records attributed to K Leosson.

5 recordsLinked to original sources
PubMed2003

Surface plasmon polariton waveguiding in random surface nanostructures.

In this study, guiding of surface plasmon polaritons excited at a gold film surface along corrugation-free channels in regions that are covered with randomly located surface scatterers, is considered using near-field microscopy for imaging of surface plasmon polariton intensity distributions at the surface. In the wavelength range 713-815 nm, we observed complete inhibition of the surface plasmon polariton propagation inside the random structures composed of individual ( approximately 70 nm high) gold bumps (and their clusters) placed on a 55 nm thick gold film with a bump density of 75 micro m-2. We demonstrate well-defined surface plasmon polariton guiding along corrugation-free 2 micro m wide channels in random structures and, in the wavelength range 738-774 nm, low-loss guiding around 20 degrees bends having a bend radius of approximately 15 micro m.

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PubMed2003

Experimental studies of surface plasmon polariton band gap effect.

Surface plasmon polaritons (SPPs) propagation at a gold film surface covered by periodic arrays of approximately 40-nm-high scatterers arranged in a triangular lattice of different periods containing straight line defects is studied using collection scanning near-field optical microscopy. The results reveal the dependence of the SPP band gap (SPPBG) effect manifested via the SPP reflection and guiding (along line defects) on the parameters of the surface structures (period, filling factor and lattice orientation). We find that the SPPBG effect is stronger along GammaK direction for all investigated periodic structures. Our results demonstrate that the SPPBG effect becomes less pronounced with a decrease of the filling factor and disappears for a filling factor close to 0.2. We also observe that the centre of the SPPBG shifts towards longer wavelengths with an increase of the lattice period.

Journal Article↗
PubMed2001

Long lived coherence in self-assembled quantum dots.

We report measurements of ultralong coherence in self-assembled quantum dots. Transient four-wave mixing experiments at 5 K show an average dephasing time of 372 ps, corresponding to a homogeneous linewidth of 3.5 microeV, which is significantly smaller than the linewidth observed in single-dot luminescence. Time-resolved luminescence measurements show a lifetime of the dot ground state of 800 ps, demonstrating the presence of pure dephasing at finite temperature. The homogeneous width is lifetime limited only at temperatures approaching 0 K.

Journal Article↗
PubMed2001

Waveguiding in surface plasmon polariton band gap structures.

Using near-field optical microscopy, we investigate propagation and scattering of surface plasmon polaritons (SPP's) excited in the wavelength range of 780-820 nm at nanostructured gold-film surfaces with areas of 200-nm-wide scatterers arranged in a 400-nm-period triangular lattice containing line defects. We observe the SPP reflection by such an area and SPP guiding along line defects at 782 nm, as well as significant deterioration of these effects is 815 nm, thereby directly demonstrating the SPP band gap effect and showing first examples of SPP channel waveguides in surface band gap structures.

Journal Article↗