23.06.2016
Doctoral Dissertation

30.6.2016 M.Sc. Svitlana Baieva (Faculty of Mathematics and Science, Physics)

Time:

30.6.2016 12:00 — 15:00


Location: Ylistonrinne , Fysiikan laitos, FYS1
Release: Dissertation: 30.6. Interaction between surface plasmon polaritons and molecules in strong coupling limit (Baieva)
M.Sc. Svitlana Baieva defends her doctoral dissertation in physics "Interaction Between Surface Plasmon Polaritons and Molecules in Strong Coupling Limit". Opponent Professor Bill Barnes (University of Exeter, UK) and custos Senior Lecturer Jussi Toppari. The doctoral dissertation is held in English.

Svitlana Baieva photo: Andrii TorgovkinM.Sc. Svitlana Baieva defends her doctoral dissertation in physics "Interaction Between Surface Plasmon Polaritons and Molecules in Strong Coupling Limit". Opponent Professor Bill Barnes (University of Exeter, UK) and custos Senior Lecturer Jussi Toppari. The doctoral dissertation is held in English.

One of the current technological challenges is the efficient integration of electronic and optical elements. Due to a diffraction, properties of optical elements are degraded or lost when they are scaled down to a size of modern electronics. However, it was realized that the miniaturization can still be done by employing surface plasmon polaritons (SPPs), which are coupled waves of free electrons in metal and electromagnetic field. Employment of organic dye molecules can add new functionalities to the plasmonic circuits. Besides this important technological issues employment of SPPs can be used to study and manipulate molecule’s properties.  

In her research Baieva has addressed fundamental questions of SPPs and molecule interactions in strong coupling regime, where the energy is no more localized into a molecule or SPP, but is shared among them between them coherently. a Rabi splitting of energy levels, evolution of the energy gap with increased interaction time, and surface plasmon coupled emission can be listed.

The properties of a biologically important pigment beta-carotene were probed with SPPs aiming to get information about the dark state of the molecule, which can play a role in energy redistribution in photosynthesis. However, no indications of this state were found. But the study was an important step in extending the SPPs-based research towards biomolecules.

The dynamics of strongly coupled modes of SPPs and fluorescent molecules was investigated by analyzing their scattered emission polarization. While the scattered emission of SPPs in samples without molecules is always transverse magnetic, the presence of molecules results in an appearance of transverse electrically polarized light. It was shown that the ratio of intensities of these two polarizations depends on molecule properties, namely on Stokes shift. The study indicates complex dynamics of the coupled state evolution involving interplay between dephasing and excited state decay times. This finding can be applied in controlling energy redistribution pathways in molecules or in plasmonics.      

Further information:
Svitlana Baieva, svitlana.v.baieva@jyu.fi, +358449470598

Svitlana Baieva graduated from Nikopol secondary school in Ukraine in 2003. Same year she began her studies in Faculty of Physics and Technology at V.N. Karazin Kharkiv National University. She graduated as Bachelor of Applied Physics in 2007. She also obtained a degree of specialist of Medical Physics from the same university. In autumn of 2008 she enrolled to Master degree program in Nanoscience at University of Jyväskylä. Baieva began PhD studies at University of Jyväskylä in 2011.

Department of Physics, University of Jyväskylä Research Report 7/2016, 78 pages + articles. ISBN 978-951-39-6676-8, ISBN 978-951-39-6677-5 (pdf). Available online: http://urn.fi/URN:ISBN:978-951-39-6677-5

Abstract

Miniaturization of optical elements and their integration to electronic circuits is limited by diffraction limit. It was realized that light being coupled to surface plasmons (SP) can overcome this limit. Employing also optically active molecules in combination with SPs can drive optical circuits to nm-scale and add functionalities. For efficient performance of plasmonic elements involving fluorescent dye molecules investigation of physics behind their interaction is of high priority. In this thesis interaction between surface plasmon polaritons (SPPs) and different dye molecules has been studied, especially within strong coupling limit, which brings in totally new physical properties in the form of hybrid SP-molecule polariton states. Strong coupling with SPPs was achieved altogether for Sulforhodamine 101 (SR101), Rhodamine 6G (R6G), TDBC and _-carotene molecules. The measurements were done in Kretschmann geometry using two complementary detection techniques. In attenuated total internal reflection (ATR) experiments

the signature of strong coupling, i.e., energy splittings in dispersion curve, was observed for samples having sufficient amount of molecules. The value of energy splitting is directly proportional to the square root of total molecular absorption, which is analogous to the strong coupling of dyes with photons inside optical microcavities. Collected scattered radiation also shows features of strong coupling. Moreover the energy gaps values are increased indicating role of interaction time. We performed also molecule excitation directly by laser in reverse Kretschmann configuration and analyzed the emission patterns revealing clear surface plasmon

coupled fluorescence of _-carotene. By increasing the concentration of _-carotene we were able to collect also surface plasmon coupled Raman scattering signal. Light scattered out due to surface roughness during the SPP propagation is always p (TM)-polarized when detected on the direction perpendicular to the surface of silver film. However, we observe polarization conversion of scattered SPP-molecule polariton in the case of R6G and TDBC dyes. We assign this rather to the properties of strongly coupled molecular state then to conversion due to surface plasmon polariton scattering on metallic film imperfections. By comparing results of different dyes we can conclude that higher Stokes shift, leading to the faster decay of the absorption state of the molecule, results in the loss of the polarization conversion returning thus the pure SPP scattering behavior.

More information

Svitlana Baieva

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svitlana.v.baieva@jyu.fi