Hakobyan M.V.,Yerevan State University |
Hakobyan M.V.,Armenian National Academy of Sciences |
Red'kov V.M.,Institute of Physics of NAS of Belarus |
Ishkhanyan A.M.,Armenian National Academy of Sciences
Laser Physics | Year: 2015
A model of the asymmetric coherent scattering process (caused by initial atomic wave-packet splitting in the momentum space) taking place at the large detuning and adiabatic course of interaction for an effective two-state system interacting with a standing wave of laser radiation is discussed. We show that the same form of initial wave-packet splitting may lead to different, in general, diffraction patterns for opposite, adiabatic and resonant, regimes of the standing-wave scattering. We show that the scattering of the Gaussian wave packet in the adiabatic case presents refraction (a limiting form of the asymmetric scattering) in contrast to the bi-refringence (the limiting case of the high-order narrowed scattering) occurring in the resonant scattering. © 2015 Astro Ltd.
Yablonskii G.P.,Institute of Physics of NAS of Belarus |
Zubialevich V.Z.,Institute of Physics of NAS of Belarus |
Lutsenko E.V.,Institute of Physics of NAS of Belarus |
Pashaev A.M.,Institute of Physics of NAS of Azerbaijan |
And 6 more authors.
Japanese Journal of Applied Physics | Year: 2011
Photoluminescence properties of barium thio- and selenogallates doped with Eu2+, Ce3+and co-doped with Eu2+ and Ce 3+were studied in a temperature range of 10-300 K and an optical excitation intensity interval of 3 × 10-4-1:25 × 10 6 W/cm2. Barium thiogallates doped with europium and co-doped by both rare-earth elements show a high thermal stability of the luminescence characteristics and significantly exceed the selenogallate analogues in respect of photoluminescence efficiency. Both thio- and selenogallates activated with the rare-earth elements demonstrate a considerable PL efficiencydroop only at high excitation levels exceeding 20 and 10 kW/cm2, respectively. Possiblereasons of the droop mechanisms are discussed. © 2011 The Japan Society of Applied Physics.
Kozik S.E.,Institute of Physics of NAS of Belarus |
Smirnov A.G.,Institute of Physics of NAS of Belarus
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011
We pursue the objective of developing a scatterometer based on focused-beam illumination and back-focal plane imaging which is suitable for characterization of truly three-dimensional objects and provides locally-resolved measurements unlike most of the state-of-the-art scatterometry tools. In this paper a full-scale simulation model for the scatterometry is proposed, comprising vector description for the illumination and imaging in terms of physical optics, and rigorous calculation of light-object interaction in the near field by a finite-difference-in-time-domain solver. Using the model we optimize the scatterometry technique to get higher sensitivity to nano-scale dimensional variations of the profile of test patterns. It has been demonstrated that asymmetry of the scattered field distribution allows one to determine separately different parameters of test structures, including refractive index, height, width, side wall, and orientation. Finally, we present a comparison of our approach with the through-focus scanning optical microscopy method. © 2011 SPIE.
Shabunya-Klyachkovskaya E.,Institute of Physics of NAS of Belarus |
Vaschenko S.,Institute of Physics of NAS of Belarus |
Stankevich V.,Institute of Physics of NAS of Belarus |
Gaponenko S.,Institute of Physics of NAS of Belarus
NATO Science for Peace and Security Series B: Physics and Biophysics | Year: 2015
The Ge/Si nanostructures with Au coating were used for surface enhanced Raman scattering by inorganic α-HgS microcrystals. The enhancement factor in the case of using these nanostructures like SERS-active substrates was higher than in the case of using Ag gel-film. We also compared Raman scattering efficiency in dependence on the laser excitation wavelength.To date, surface enhanced Raman scattering (SERS) is known as one of the most sensitive technique for the identification of small quantities of analytes. Since organic molecules are much smaller than the nanoobjects used like SERS-active substrates, SERS is often used for the identification of the organic art pigments. To identify inorganic art pigments, micro-Raman spectroscopy is usually applied.In our recent work (Klyachkovskaya et al., Plasmonics 6:413-418, 2011) we were able to get 100-fold enhancement of the Raman spectra of ultramarine microcrystals. In addition, it was shown that self-assembled Ge/Si nanostructures coated with a noble metal can be used like very perspective SERS-active substrates. In this paper, we use these substrates for surface enhanced Raman scattering by inorganic α-HgS microcrystals (vermilion). In addition we compare Raman scattering efficiency in dependence on the type of SERS-active substrate and the laser excitation wavelength.So, two types of SERS-active substrate were used for the experiments. The first of them were the self-assembled Ge/Si nanostructures and the second one were the gelfilms of the silver nanoparticles (10-25 nm in size). The Ge/Si nanostructures were grown by chemical vapor deposition (Stoica et al., Nanotechnology 18:455307, 2007). Silver sol has been prepared via Ag ions reduction with dextroglucose under heating (Fang et al., Chem. Phys. Lett. 401:271-275, 2005). The Raman measurements were performed in the backscattering configuration at room temperature. (figure presented) The Nd:LSB laser (531 nm) as well as the He-Ne laser (632.8 nm) were used for Raman spectra excitation. The registration system consists of a spectrograph with a diffraction grating 1,200 grooves per mm (Solar TII S3901) and a CCD matrix, which is cooled with liquid nitrogen (Princeton instruments).The bands at 262 cm-1 (secondary vibration of A1), 296 cm-1 (E2.LO/ optical phonon transverse vibrations) and 351 cm-1 (E1(TO) secondary longitudinal oscillations) occur in the Raman spectra. When Raman spectra are excited with the He-Ne laser (632.8 nm), the intensity increases in 15 fold in the case of using the Si/Ge nanostructures like the SERS-active substrate and in five fold in the case of using the silver gel-film as the substrate (see Fig. 32.1). In the case of using the Nd:LSB laser (531 nm) for Raman spectra excitation, the intensity increases only 1.9 and 1.7 fold, respectively (see the inset in the Fig. 32.1).The dependence of the enhancement on the type of the SERS-active substrate may be related to their topography. The Ge islands on the Si substrate have a quadrangular pyramid shape, which leads to resonance with dipole plasma oscillations (Sajanlal et al., Nano Rev 2(0), 2011). In result, the local electric field at the top of the “pyramids” is essentially magnified. Additionally, the gold is the inert metal unlike the silver which is easily oxidized. As for the dependence of the Raman intensity on the excitation source, it’s probably due to the fact that the He-Ne laser has a narrow contour of the excitation line and works in single mode unlike the Nd: LSB one, that has quite wide contour of the excitation line and excite Raman scattering over a wide range.So, obtained results can be applied for the optimization SERS technique for the identification of the inorganic pigments in the Cultural heritage objects. The authors are grateful to Prof. D. Grutzmacher for providing the Ge/Si nanostructures for the experiments. © Springer Science+Business Media Dordrecht 2015.