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Projekt
Ultraintense Nonlinear Optics on Dielectrics and Structured Metals
Antragsteller
Professor Dr. Manfred Fiebig
Fachliche Zuordnung
Optik, Quantenoptik und Physik der Atome, Moleküle und Plasmen
Förderung
Förderung von 2007 bis 2011
Projektkennung
Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 5471245
The development of ultraintense lasers emitting sub-picosecond pulses boosted the potential of nonlinear optics as a tool for investigating the properties of condensed-matter systems in the (near-) visible range. On the one hand, nonlinear optics with ultrashort pulses allows one to probe the response of such systems upon intense optical excitation (a pump pulse) with unrivaled temporal resolution while using the additional degrees of freedom inherent to a multi-photon experiment in the probe process: accessibility to "forbidden" states and an improved distinction between electronic transitions are gained. On the other hand, the high peak intensity of a sub-picosecond laser pulse leads to detectable nonlinear optical intensities even when low-dimensional or confined systems with an inherently smaller signal yield are studied. Here we exploit both of these advantages in the investigation of two systems of great current interest.A) LiNbO3 is a transparent material in which crystallographic defects of intrinsic or extrinsic nature lead to a number of unusual properties such as photoinduced modification of the complex refractive index. The progression of migration and recombination of the charge carriers following the photoexcitation and manifesting eventually as the photorefractive effect are entirely unknown. We will investigate the photocarrier dynamics in pump-and-probe experiments using nonlinear optics for probing the electronic transitions involved in the carrier migration and recombination process.B) Metamaterials are artificial crystals with sub wave length-scale building blocks which can exhibit qualitatively new physical effects such as non-unity permeability and permittivity at optical frequencies. The presence of confinement-related eigenstates are essential for the manifestation of these effects. However, the nature of these eigenstates is discussed quite controversially at present. We will probe these modes by nonlinear optical spectroscopy using simple geometric arguments for the distinction between inductance-capacitance (LC) oscillator modes, surface-induced states, and plasmon resonances. Subsequently, we plan to determine the dispersion of an anomalous confinement-related polariton branch quantitatively with high spectral resolution.
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