Tal Schwartz Research Group

Laboratory for Molecular Nano-Optics

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.

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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.

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Scattering from Molecular Ensembles

We study the scattering properties of molecules embedded in an optical cavity under strong coupling conditions, where the collective interaction between the molecules and the cavity gives rise to composite light−matter excitations known as cavity polaritons. The polaritonic states exhibit strong resonant Rayleigh scattering. The polaritonic wave functions in such systems are delocalized, corresponding to the collective scattering of each photon from a large ensemble of molecules.

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Terahertz Strong Coupling

Strong coupling with collective, inter-molecular vibrations occurring in organic materials in the low-terahertz region (≲1012 Hz). Using a cavity filled with α-lactose molecules, we take strong coupling into a new class of materials and processes, including skeletal polymer motions, protein dynamics, metal organic frameworks and other materials, in which collective, spatially extended degrees of freedom participate in the dynamics.

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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.

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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.