In nature, light and matter are constantly interacting – photons are absorbed or emitted, they induce chemical reactions and drive the transport of charges. When such interactions occur inside a wavelength-scale region confined by a photonic nanostructure they can change dramatically, giving rise to new and exciting effects. In our research, we explore artificial structures with which we may produce complex materials with new properties and control the interaction of light and matter. We focus on several aspects of this theme, which lie at the meeting point of chemistry, quantum physics, optics and materials science.

Selected Research Topics

  • Strong Interaction of Molecules with Light

    We investigate the optical properties of organic molecules (dyes) coupled to optical devices, aiming toward understanding quantum many-body processes in such hybrid systems and controlling these interactions. Gaining such control is important for photo-chemistry, light-harvesting and organic light-emitting devices.

Cavity with molecule cartoon 3

  • Polariton Transport

    While excitations in organic materials are localized on individual molecules, under strong light-molecule coupling, cavity polaritons are formed, with wave functions extending beyond the molecular scale. Using time-resolved microscopy we follow the motion of polaritons in real-time to show that this coupling induces long-range transport in organic materials and propagation over several microns.

Polariton Transport 3

  • Controlling Resonant Energy Transfer

    Energy transfer between molecules is a process by which a donor molecule transmits its excitation energy to a nearby acceptor molecule. This can be a non-radiative process in which the excitation energy of a donor is directly transferred to an acceptor via dipole-dipole interaction, without the emission and reabsorption of free photons. By designing special metallic nanostructures in which plasmons are coupled to cavity photons, we can enhance the range of energy transfer from the typical nanometric range of Forster Resonant Energy Transfer (FRET) by one to two orders of magnitude, achieving energy transfer over distances which begin to approach the optical wavelength.

FRET cartoon2

  • Optical Properties of Metallic Nanoparticle-Clusters

    A nanometer-sized gold particle has a very distinct color, completely different from the color of bulk gold. The reason is that when we shape a metal on a nanometric scale it supports localized plasmon modes that depend on properties such as geometry and size. In our research we explore the assembly of such nanoparticles into well-defined clusters in order to achieve composite materials with new optical properties.

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  • Optomechanical Oscillations

    We study mechanical vibrations in planar Fabry-Perot microcavities made of metallic mirrors and a polymer spacer experimentally, using broadband pump-probe spectroscopy. These acoustic waves oscillate on a picosecond time-scale and result in spectral oscillations of the cavity transmission spectrum. We find that the oscillations are initiated at the metal mirrors and that their temporal dynamics match the elastic modes of the polymer layer, indicating that mechanical momentum is transferred within the structure. Such structures combine the strong optical absorption of metals with the elasticity and the processability of polymers, which opens the door to a new class of optomechanical devices.

Optoacoustics