Combining nanooptical fields and coherent spectroscopy on systems with delocalized excitons
20 Feb 2012-Proceedings of SPIE (International Society for Optics and Photonics)-Vol. 8260, pp 278-285
TL;DR: In this paper, the authors combine coherent two-dimensional spectroscopy and nanoplasmonics to localize optical fields on a nanoscale and propose new experiments, such as the two dimensional spectra containing spatial resolution via localized fields.
Abstract: For nanostructures such as semiconductor quantum dot emitters or biological systems like light harvesting complexes (photosynthesis) the coupling between individual constituents leads to the formation of delocalized exciton states. Coherent two dimensional spectroscopy is a versatile tool to investigate the structure of the excitonic states, whereas nanoplasmonics allows to localize optical fields on a nanoscale: We combine these two methods in a theoretical study and propose new experiments, such as the two dimensional spectra containing spatial resolution via localized fields. Using post processing of different spectra with localized fields, we can enhance certain spectroscopic features in standard coherent spectroscopy, e.g. by suppressing unwanted resonances.
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28 Jan 2013
Abstract: Recently, optical technologies are a rapidly developing branch of physics with a lot of applications in modern lifestyle. Efficient devices consist of optical components with spatial dimensions of only a few nanometers. The focus of this purely theoretical thesis is to investigate and to control the optical excitations in metal nanostructures simultaneously in space and time under the influence of light and applications of this spatiotemporal control. The results of this thesis are composed of three topics. The first topic deals with properties of metal nanostructures. A theoretical model system for metals is introduced and as first result, the band structure and dipole transition matrix elements of silver are calculated. Plasmonic effects of metal (hybrid) nanospheres are examined in preparation for the mechanisms of controlling light. Nanoplasmonics describes optical effects based on plasma oscillations of nanostructured metal systems. These systems can keep the optical energy concentrated on nanometer scale and femtosecond scale, enabled by modes called surface plasmons. For spatiotemporally localized enhancement of the electromagnetic field, material properties and geometry settings have to be considered: For example, resonances of different metals at different wavelengths are examined. It is also shown that nonresonant metal layers for the considered wavelengths can transfer field enhancement on the surface over a long distance and that decreasing enhancements due to the screening of thick coatings can be compensated by coupling of two nanospheres. The second topic deals with confining optical excitations simultaneously on a nanometer length scale and on a femtosecond time scale. For conventional light sources, however, the spatial resolution of optical measurements is limited by the wavelength of the incident light. Still, achieving electronic control below the diffraction limit is desirable because it opens a number of novel methods in investigating nanosystems. It becomes possible by combining nanoplasmonics with pulse shaping techniques. Interferences of near and far fields and polarization effects serve as control mechanism. To find the pulses that supply the desired localization, in the central part of the thesis a genetic algorithm that optimizes the shape of the incoming pulses is generated. Different geometries show varying optimization quality. Good localizations are achieved by using metal tips or antenna-like geometries that guide excitations into the nanostructure. The last topic is an application of the achieved spatiotemporal control. Control is applied to complex (hybrid) nanostructures (e.g. semiconductor quantum dots or pigments embedded in proteins such as in light harvesting complexes), that serve as optical emitters. If they are placed in vicinity, they couple via Coulomb forces. This dipole-dipole coupling on nanometer scale between individual emitters leads to the formation of new collective hybridized quantum states that are delocalized over the entire nanostructure. The main result of this work is a new kind of quantum state tomography that disentangles the individual contributions of the coupled emitters in a spatially extended nanostructure from the collective optical response via localized near field spectroscopy. A coherent nonlinear multidimensional spectroscopy method (the double quantum coherence) is combined with light concentrating techniques. Many-particle wave functions of coupled quantum dots for exciton as well as for biexciton states can be reconstructed (up to an arbitrary phase) by finding the expansion coefficients of the basis representation by using a sequence of three polarization shaped light pulses with controlled envelopes and phases. The quality of reconstruction depends among others on the quality of spatiotemporal control and on influences of neighboring resonances. Filtering methods can reduce these influences and thus improve the quality of reconstruction. In all, more information about the system can be revealed than by using two-dimensional spectroscopy or localization alone.
5 citations
TL;DR: In this paper, a two-dimensional coherent spectroscopy method was proposed to measure the dipole-forbidden electronic transitions of quantum dots and trace their relaxation behavior in nanosystems.
Abstract: The correct understanding of the electronic structure and relaxation behavior in nanosystems is essential for technical applications We propose a spectroscopic method to measure the dipole-forbidden electronic transitions of quantum dots and trace their relaxation behavior Therefore, we utilize two-dimensional coherent spectroscopy, which is an advantageous tool to get information about the dynamics of exciton densities and coherences in nanoscopic structures In combination with nanoplasmonics, it enables excitation of dipole-forbidden states A nanoplasmonic dolmen structure allows us to dynamically excite either dipole-allowed and dipole forbidden states selectively In combination with two-dimensional spectroscopy, this gives us additional control over excitation and tracing relaxation involving dipole-forbidden states in nanoscopic systems
4 citations
Additional excerpts
...The total transition matrix element M̃mn = μ̃mn + Q̃mn between the states |n〉 and |m〉 is given by μ̃mn = μmn ·E ν r(0), (10) Q̃mn = Qmn : ∇E S,ν r (0) (11)...
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TL;DR: In this article, the strong and ultrafast laser pulse excitation of a molecular chain in close vicinity to a spherical metal nano-particle (MNP) is studied theoretically.
Abstract: The strong and ultrafast laser pulse excitation of a molecular chain in close vicinity to a spherical metal nano-particle (MNP) is studied theoretically. Due to local-field enhancement around the MNP, pronounced excited-state formation has to be expected for the part of the chain which is in proximity to the MNP. Here, the description of this phenomenon will be based on a uniform quantum theory of the MNP–molecule system. It accounts for local-field effects due to direct consideration of the strong excitation energy transfer coupling between the MNP and the various molecules. The molecule–MNP distances are chosen in such a way as to achieve a correct description of the MNP via dipole–plasmon excitations. Short plasmon life-times are incorporated in the framework of a density matrix approach. By extending earlier work the present description allows for multi-exciton formation and multiple dipole–plasmon excitation. The region of less intense and not-too-short optical excitation is identified as being best suited for excitation energy localization in the chain.
3 citations
References
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TL;DR: In this paper, E.D. Palik and R.R. Potter, Basic Parameters for Measuring Optical Properties, and W.W.Hunter, Measurement of Optical Constants in the Vacuum Ultraviolet Spectral Region.
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17,491 citations
TL;DR: In this paper, the authors describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment.
Abstract: The optical properties of metal nanoparticles have long been of interest in physical chemistry, starting with Faraday's investigations of colloidal gold in the middle 1800s. More recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize noble metal nanoparticles with a wide range of sizes, shapes, and dielectric environments. In this feature article, we describe recent progress in the theory of nanoparticle optical properties, particularly methods for solving Maxwell's equations for light scattering from particles of arbitrary shape in a complex environment. Included is a description of the qualitative features of dipole and quadrupole plasmon resonances for spherical particles; a discussion of analytical and numerical methods for calculating extinction and scattering cross-sections, local fields, and other optical properties for nonspherical particles; and a survey of applications to problems of recent interest involving triangula...
9,086 citations
Book•
15 Jan 1995
TL;DR: In this article, the authors present a simulation of the optical response functions of a multilevel system with relaxation in a multimode Brownian Oscillator Model and a wavepacket analysis of nonimpulsive measurements.
Abstract: 1. Introduction 2. Quantum Dynamics in Hilbert Space 3. The Density Operator and Quantum Dynamics in Liouville Space 4. Quantum Electrodynamics, Optical Polarization, and Nonlinear Spectroscopy 5. Nonlinear Response Functions and Optical Susceptibilities 6. The Optical Response Functions of a Multilevel System with Relaxation 7. Semiclassical Simulation of the Optical Response Functions 8. The Cumulant Expansion and the Multimode Brownian Oscillator Model 9. Fluorescence, Spontaneous-Raman and Coherent-Raman Spectroscopy 10. Selective Elimination of Inhomogeneous Broadening Photon Echoes 11. Resonant Gratings, Pump-Probe, and Hole Burning Spectroscopy 12. Wavepacket Dynamics in Liouville Space The Wigner Representation 13. Wavepacket Analysis of Nonimpulsive Measurements 14. Off-Resonance Raman Scattering 15. Polarization Spectroscopy Birefringence and Dichroism 16. Nonlinear Response of Molecular Assemblies The Local-Field Approximation 17. Many Body and Cooperative Effects in the Nonlinear Response
4,011 citations
"Combining nanooptical fields and co..." refers background in this paper
...4b).(16) In a two dimensional spectrum not only energies of single and biexcitons but also the correlations between their states become visible....
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Book•
01 Jan 1973
2,928 citations
"Combining nanooptical fields and co..." refers methods in this paper
...We use an adaptive mutation step size Δa that varies depending on the average of the step sizes of the previous 100 children.(8) Thus we quickly approach the minimum of the cost function and reach the lowest values with finer steps....
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TL;DR: Optical antennas are devices that convert freely propagating optical radiation into localized energy, and vice versa as mentioned in this paper, and hold promise for enhancing the performance and efficiency of photodetection, light emission and sensing.
Abstract: Optical antennas are devices that convert freely propagating optical radiation into localized energy, and vice versa. They enable the control and manipulation of optical fields at the nanometre scale, and hold promise for enhancing the performance and efficiency of photodetection, light emission and sensing. Although many of the properties and parameters of optical antennas are similar to their radiowave and microwave counterparts, they have important differences resulting from their small size and the resonant properties of metal nanostructures. This Review summarizes the physical properties of optical antennas, provides a summary of some of the most important recent developments in the field, discusses the potential applications and identifies the future challenges and opportunities.
2,557 citations