Christian Matyssek

In Situ Observation of Plasmon Tuning in a Single Gold Nanoparticle during Controlled Melting

In this Letter we study the relations among shape, symmetry, and plasmon resonance shift in a single gold nanoparticle during laser melting. A beam of an argon ion laser is focused on a selected particle, while its optical and shape properties can be observed with the help of a combined dark-field/photoluminescence microscope and an atomic force microscope, respectively. Starting from a spherical shape, radiation pressure forms the melting gold particle into an upright standing rod on a glass substrate, showing a characteristic dipole scattering pattern. A red-shift of the photoluminescence signal and the scattering spectrum is observed. The melting process can be controlled allowing the formation of different particle heights and plasmon resonance shifts. In situ tuning of the plasmon resonance of individual particles is possible with this reversible melting process.

The T-Matrix method in electron energy loss and cathodoluminescence spectroscopy calculations for metallic nano-particles

In this paper, we present the application of the T-Matrix method (TMM) for the calculation of Electron Energy Loss Spectra (EELS), cathodoluminescence spectra (CLS) and far-field patterns produced by metallic nano-particles. Being frequently used in electromagnetic scattering calculations, the TMM provides an efficient tool for EELS calculations as well and can be employed, e.g. for the investigation of nano-antennas.

Current sheets in the Discontinuous Galerkin Time-Domain method: an application to graphene

We describe the treatment of thin conductive sheets within the Discontinuous Galerkin Time-Domain (DGTD) method for solving the Maxwell equations and apply this approach to the efficient computation of the optical properties of graphene-based systems. In particular, we show that a thin conductive sheet can be handled by incorporating the associated jump conditions of the electromagnetic field into the numerical flux of the DGTD approach. This results in a flexible and efficient numerical scheme that can be applied to a number of systems. Specifically, we show how to treat individual graphene sheets on substrates as well as finite stacks of alternating graphene and dielectric layers by modeling the dispersive and dissipative properties of graphene via a two-term critical-point model for its electrostatically doped conductivity.

Near-field optical microscopy of femtosecond-laser-reshaped silver nanoparticles in dielectric matrix

AbstractSamples containing single silver nanoparticles have been irradiated by intense femtosecond laser pulses to gain a persistent transformation of their shape to ellipsoidal forms. Irradiated and non-irradiated regions of these samples have been analyzed by microscope spectrometry as well as near-field scanning optical microscopy (NSOM) with several wavelengths and different linear polarizations. The results show the outstanding capability of NSOM technique to detect the individual shape of transformed metallic nanoparticles and to analyze their orientation and aspect ratio.