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Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Nanooptik

(Quantum) Hybrid Systems

 

Staff members:  Oliver Neitzke, Günter Kewes
Collaborators: Yan Lu, Andreas Ott and Matthias Ballauff
Helmholtz-Zentrum Berlin

 

Fundings through:

 

 

 

SFB 951 "HIOS"

General concept of Hybrid Inorganic/Organic Systems (HIOS)

The Collaborative Research Centre HIOS (SFB 951) is an interdisciplinary effort bringing together scientists with complementary expertise from three universities and four non-university institutions. The goal is the merger of inorganic semiconductors, conjugated organic materials, and metal nanostructures into novel hybrid structures. Elucidating and tailoring the fundamental chemical, electronic, and photonic interactions in these systems will enable us the development of functional elements exhibiting superior opto-electronic functionalities not achievable with any of the individual material classes alone.


 

Subproject B1


The goal of this project is to study plasmon-enhanced transfer processes in HIOS. These are input/ output processes of photons to/from organic molecules, exciton transfer across inorganic/ organic interfaces in the incoherent – possibly coherent – regime, and transfer of energy between separated organic molecules along plasmonic wires. In addition to this, absorption and fluorescence rates of the conjugated organic molecule itself will be controlled as well, while simultaneously lowered excitation powers can reduce photobleaching effects.



FEM_nanoantenna.jpg nanowire.jpg
Fig. 2: Finite Element Method calculation of field-distribution of a plasmonic nanoantenna: electromagnetic hotspot in the antenna-gap enables the concentration of electromagnetic energy well below the diffraction limit. This will enhance the excitation-efficiencies. Fig. 3: Silver nanowire surrounded by a shell of conjugated molecules (image: D.M.Eisele, Dissertation, HU Berlin 2009): Plasmonic waveguides guide light on sub- λ length scales. Thus they are possible interconnects for highly integrated optoelectronic circuits.


B1.jpg
Fig. 4: (a)–(c) Schematic approaches for the assembly of hybrid metallic/inorganic/organic structures.

 

Subproject B2


The main goal of this subproject is to fabricate the smallest object capable of providing a coherent amplification of radiation, i.e., a surface plasmon polariton laser (spaser). The first investigated spaser structures will consist of a single spherical or rod-shaped gold particle surrounded by a layered structure containing conjugated organic molecules as gain medium in a SiO2 matrix. Optical excitation will be applied. After optimization of optically excited spacers, we will strive for an important step forward, i.e., realization of an electrically excited spaser. Apart from many fascinating new possiblities which open up, when active sub- λ optic elements are realized, spasers also promise to be extremely fast switching devices in the range of about 100 fs.

 

spaser_scheme.jpg Fig. 5: spaser-scheme: a metal nanoparticle able to support localized surface plasmon modes (white line: dipole-mode, black line: quadrupole-mode) acts as a resonator for plasmons. A surrounding shell is doped with emitters (red arrows) which are pumped from the outside. The emitters populate the plasmon-field rather than emitting in the far-field.


spaser_principle.jpg
Fig. 6: diagram and TEM image of hybrid Au@dye-doped SiO2 core/shell particles.

 

 

S. Wu, A. W. Schell, M. Lublow, J. Kaiser, T. Aichele, S. Schietinger, F. Polzer, S. Kühn, X. Guo, O. Benson, M. Ballauff, and Y. Lu, “Silica-coated Au/Ag Nanorods with Tunable Surface Plasmon Bands for Nanoplasmonics with Single Particles“, Colloid Polym. Sci. 291, 585 (2013).

G. Kewes, M. Schoengen, G. Mazzamuto, O. Neitzke, R. Schönfeld, A. W. Schell, J. Probst, J. Wolters, B. Löchel, C. Toninelli, O. Benson, "Key components for nano-assembled plasmon-excited single molecule non-linear devices", arXiv 1501.04788 (2014)

G. Kewes, R. Rodríguez-Oliveros, K. Höfner, A. Kuhlicke, O. Benson, and K. Busch, “Threshold Limitations of the SPASER”, arXiv:1408.7054 (2014).