Hayk Harutyunyan

Learn More
We investigate graphene and graphene layers on different substrates by monochromatic and white-light confocal Rayleigh scattering microscopy. The image contrast depends sensitively on the dielectric properties of the sample as well as the substrate geometry and can be described quantitatively using the complex refractive index of bulk graphite. For a few(More)
It is widely believed that the reflection minimum in a Kretschmann-Raether experiment results from direct coupling into surface plasmon polariton modes. Our experimental results provide a surprising discrepancy between the leakage radiation patterns of surface plasmon polaritons (SPPs) launched on a layered gold/germanium film compared to the K-R minimum,(More)
Ensemble and single-molecule spectroscopy demonstrates that both emission and absorption of peridinin-chlorophyll-protein photosynthetic antennae can be largely enhanced through plasmonic interactions. We find up to 18-fold increase of the chlorophyll fluorescence for complexes placed near a silver metal layer. This enhancement, which leaves no measurable(More)
We introduce and experimentally demonstrate the concept of multifrequency optical antennas that are designed for controlling the nonlinear response of materials. These antennas consist of two arms of different lengths, each resonant with one of the incoming frequencies. They are embedded in a nonlinear medium (indium tin oxide) that acts as a receiver.(More)
We show that new low-energy photoluminescence (PL) bands can be created in the spectra of semiconducting single-walled carbon nanotubes by intense pulsed excitation. The new bands are attributed to PL from different nominally dark excitons that are "brightened" because of a defect-induced mixing of states with different parity and/or spin. Time-resolved PL(More)
Dark-field microscopy is a background-free imaging method that provides high sensitivity and a large signal-to-noise ratio. It finds application in nanoscale detection, biophysics and biosensing, particle tracking, single molecule spectroscopy, X-ray imaging, and failure analysis of materials. In dark-field microscopy, the unscattered light path is(More)
We introduce an active, all-optical method for controlling the intensity and directionality of light scattering from single nanostructures. The method is based on the coherent interplay between linear light scattering and second-harmonic generation. The intensity and directionality of scattered light can be controlled by the phase delay and the relative(More)
We investigate the nonlinear optical response of a noble metal surface. We derive the components of the third-order nonlinear susceptibility and determine an absolute value of χ((3))≈0.2 nm(2) V(-2), a value that is more than two orders of magnitude larger than the values found for typical nonlinear laser crystals. Using nonlinear four-wave mixing (4WM)(More)
The interaction of light and matter in metallic nanosystems is mediated by the collective oscillation of surface electrons, called plasmons. After excitation, plasmons are absorbed by the metal electrons through inter- and intraband transitions, creating a highly non-thermal distribution of electrons. The electron population then decays through(More)
H. Bräuning, A. Bräuning-Demian, G. Bednarz, F. Bosch, X. Cai, C. Cohen, D. Dauvergne, A. Gumberidze, H. Harutyunyan, R. Kirsch, C. Kozhuharov, D. Liesen, P.H. Mokler, J.-P. Rozet, Z. Stachura, Th. Stöhlker, M. Terasawa, S. Toleikis, A. Warczak, ESR-Team JLU Giessen (Germany), GSI (Germany), University of Cracow (Poland) IMP Lanzhou (China), GPS Paris(More)