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Дата изменения: Wed Mar 12 16:11:49 2008 Дата индексирования: Mon Oct 1 19:28:00 2012 Кодировка: |
Story by Prof. Aktsipetrov: |
The
foundation of our laboratory traces back to 1980 when Professor Leonid
V. Keldysh proposed me to organize at his Chair of Quantum Radiophysics
new group aimed at studies of Surface Nonlinear Optics. For these more then
fifteen years of our activity several pioneer works have been done in this
area. |
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1
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The start of our surface and thin film studies has been made on the observation of Second-Harmonic Generation (SHG) from monolayer Langmuir-Blodgett (LB) films. Further Nonlinear Optics of the LB films was initiated by this paper:
Later our results on SHG have been generalized on multilayer Langmuir-Blodgett films.
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2
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In the early 1980's the intensive investigation of the mechanisms of surface-enhanced nonlinear-optical phenomena was one of the main objectives of our experimental activity. These studies have brought to the first time observation of - photoactivation of Surface-enhanced second harmonic generation (SESHG) at silver-electrolyte interface:
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3
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In 1983 we re-discovered DC-electric-field induced surface Second Harmonic generation (EFISH) phenomenon. Actually EFISH effect was observed, for the first time, by N. Bloembergen and co-workers [C.H. Lee, R.K. Chang, and N. Bloembergen, Phys. Rev. Lett. 18 167 (1967)]. However, Bloembergen's results remained unnoticed for a long time. The 1981 discovery of surface-enhanced second harmonic generation by Y.R. Shen and co-workers [C.K. Chen, A.R.B. de Castro, and Y.R. Shen, Phys. Rev. Lett. 46 145 (1981)] rejuvenated interest in this problem. Going further in studies of surface-enhanced SHG we have observed the effect of the DC-electric-field induced surface enhanced SHG at silver-electrolyte interface.
Later EFISH has been observed and systematically studied at Column IV semiconductor-electrolyte interfaces.
New step in EFISH studies has been done after ten years when we proposed to refuse from electrochemical cell in these experiments and apply the bias to the interface in metal-oxide-semiconductor (MOS) structures.
As a final chapter of this more then ten-year story the electromodulation SHG spectroscopy of buried interfaces in planar MOS structures with semi-transparent metal gate electrode has been developed.
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4
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Up to the mid 1980's not much attention was paid to the role of the external influences in Surface SHG from materials sensitive to such factors like external bias discussed above, magnetic field, external illumination, etЯ. Following the observation of the EFISH phenomena we investigated, for the first, to our knowledge, time, photoinduced effects in SHG from photo(electro)chromic material: bacteriorhodopsine thin films and proposed to use the SHG probe as nondestructive readout of optical memories.
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5
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The logical expansion of the electroinduced SHG studies was the search of the magnetoinduced effects in SHG from magnetic materials initiated by theoretical papers by A. Zvezdin and N. Achmediev. As a result of this search, DC-magnetic- field induced SHG and Giant nonlinear-optical magnetic Kerr effect has been observed.
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6
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The separation of the surface and bulk contributions to the total reflected SHG response was the key problem of the SHG diagnostics of surfaces and interfaces in the mid 1980's. The idea of this separation was announced by H. Tom, T. Heinz and Y. Shen in their paper [Phys. Rev. Lett. 51 1983 (1983)]. Following this idea, the systematic phenomenological theory of anisotropic quadratic response from the surface of centrosymmetric semiconductors has been developed in our paper:
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7
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Another T. Heinz and coworker's paper on the SHG probe of surface reconstruction phase transition [T.F. Heinz, M.M.T. Loy, and W.A. Thompson, Phys. Rev. Lett. 54, 63 (1985)] has triggered our application of this nonlinear-optical method to the studies of phase transitions in thin (down to monolayer) solid films. Thus ferroelectric and insulator-to-metal phase transitions in thin films have been studied.
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8
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The systematic studies of SHG from metallic nanocrystals and semiconductor quantum dots have brought to the understanding of the role of quantum chaos in quadratic nonlinear response of electrons in nanostructures.
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9
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The systematic studies of size effects in second-harmonic generation from Si-SiO2 structures have brought to the prediction of new type of nonlocality: Optical Casimir nonlocality which originates from the nonlocal electron-electron interaction via virtual photons of quantized electromagnetic field.
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