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.


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:
  • O.A. Aktsipetrov, A.A. Akhmediev, E.D. Mishina, and V.R. Novak. Second harmonic generation from Langmuir-Blodgett monolayer. Pis'ma Zh. Exsp. Teor. Fiz. 37, 175 (1983) (JETP Lett. 37, 207 (1983));
and paper by F. Kajsar, J. Messier, J. Zyss, and I. Ledoux [Opt. Comm., 45, 133 (1983)] where third harmonic generation from thick LB film has been studied.

Later our results on SHG have been generalized on multilayer Langmuir-Blodgett films.

  • O.A. Aktsipetrov, N.N. Akhmediev, I.M. Baranova, E.D. Mishina, and V.R. Novak. Structure of Langmuir-Blodgett films studied by second harmonic generation. Zh. Exsp. Teor. Fiz. 89, 911 (1985) (Sov. Phys. JETP, 62, 524 (1985)).


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:

  • O.A. Aktsipetrov and E.D. Mishina. Photoactivation of surface-enhanced second harmonic and surface-enhanced Raman scattering. Pis'ma Zh. Exsp. Teor. Fiz. 38, 422 (1983) (JETP Lett. 38, 535 (1983));
- enhancement of SHG by Lightning rod effect at metal surface with large curvature:
  • O.A. Aktsipetrov, I.M. Baranova, E.D. Mishina, and A.V. Petukhov. "Lightning rod" effect in surface-enhanced second harmonic generation. Pis'ma Zh. Exsp. Teor. Fiz. 40, 240 (1984) (JETP Lett. 40, 240 (1984));
- enhancement of SHG in small metal particles with noncentosymmetric geometrical shape:
  • O.A. Aktsipetrov, I.M. Baranova, S.S. Elovikov, P.V. Elyutin, D.A. Esikov, A.A. Nikulin, and N.N. Fominykh. New mechanism of surface-enhanced second harmonic generation in small metallic particles. Phys. Lett. A 117, 239 (1986);
- surface-enhanced second harmonic generation in cold deposited silver films:
  • O.A. Aktsipetrov, E.M. Dubinina, S.S. Elovikov, D.A. Esikov, and N.N. Fominykh. Surface-enhanced second harmonic generation in cold deposited films; mechanism for surface enchancement. Pis'ma Zh. Exsp. Teor. Fiz. 44, 371 (1986) (JETP Lett. 44, 475 (1986)).


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.

  • O.A. Aktsipetrov, E.D. Mishina, and A.V. Petukhov. Electric-field-induced reflection in silver accompanying surface-enhanced second harmonic generation. Pis'ma Zh. Exsp. Teor. Fiz. 37, 592 (1983) (JETP Lett. 37, 707 (1983)).

Later EFISH has been observed and systematically studied at Column IV semiconductor-electrolyte interfaces.

  • O.A. Aktsipetrov and E.D. Mishina. Nonlinear optical electroreflectance in Germanium and Silicon. Dokl. Akad. Nauk SSSR, 274, 65 (1984) (Sov. Phys. Dokl. 29, 37 (1984)).

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.

  • O.A. Aktsipetrov, A.A. Fedyanin, V.N. Golovkina, and T.V. Murzina. Optical second- harmonic generation induced by a dc electric field at the Si-SiO2 interface. Optics Letters, 19, 1450 (1994).

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.

  • J.I. Dadap, X.F. Hu, M.H. Anderson, M.C. Downer, J.K. Lowell, and O.A. Aktsipetrov. Optical second-harmonic electroreflectance spectroscopy of a Si(001) metal-oxide- semiconductor structure. Phys. Rev. B 53, 7607R (1996).


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, etŮ. 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.
  • O.A. Aktsipetrov, A.A. Akhmediev, N.N. Vsevolodov, D.A. Esikov, and D.A. Shutov. Photochromism in nonlinear optics: photocontrolled second harmonic generation in bacteriorhodopsine molecules. Dokl. Akad. Nauk SSSR, 293, 572 (1987) (Sov. Phys. Dokl. 32, 219 (1987)).


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.
  • O.A. Aktsipetrov, O.V. Braginskii, and D.A. Esikov. Nonlinear optics of gyrotropic media: second harmonic generation in rare-earth iron garnets. Kvantovaya Electron. 17, 320 (1990) (Sov. J. Quantum Electron. 20, 259 (1990)).


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:
  • O.A. Aktsipetrov, I.M. Baranova, and Yu.A. Il'inskii. Surface contribution to the generation of reflected second harmonic generation from centrosymmetric semiconductors. Zh. Exsp. Teor. Fiz. 91, 287 (1986) (Sov. Phys. JETP, 64, 167 (1986)).


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.
  • O.A. Aktsipetrov, S.A. Apukhtina, A.A. Nikulin, K.A. Vorotilov, E.D. Mishina, and A.S. Sigov. Generation of reflected second harmonic and phase transition in ferroelectric thin films. Pis'ma Zh. Eksp. Teor. Fiz. 54, 562 (1991) (JETP Lett. 54, 563 (1991)).
  • O.A. Aktsipetrov, V.V. Vereta, L.I. Daikhin, M.D. Levi, A.V. Ermushev, and A.V. Petukhov. Generation of reflected second harmonic and insulator-metal transition in conducting polymer films. Pis'ma Zh. Eksp. Teor. Fiz. 54, 175 (1991) (JETP Lett. 54, 171 (1991).


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.
  • O.A. Aktsipetrov, P.V. Elyutin, A.A. Nikulin, and E.A. Ostrovskaya. Size effects in optical second-harmonic generation by metallic nanocrystals and semiconductor quantum dots: The role of quantum chaotic dynamics. Phys. Rev. B 51, 17591 (1995).


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.
  • O.A. Aktsipetrov, A.A. Fedyanin, E.D. Mishina, A.A. Nikulin, A.N. Rubtsov, C.W. van Hasselt, M.A.C. Devillers, and Th. Rasing. Macroscopic size effects in second harmonic generation from Si(111) coated by thin oxide films: the role of optical Casimir nonlocality. Phys. Rev. Lett. 78, 46 (1997).

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