V. V. Toporov

High power gain for stimulated Raman amplification in CuAlS2

The spontaneous Raman spectra of the chalcopyrite structure crystal CuAlS2, which is promising for nonlinear optical applications, has been investigated at 8 and 300 K. The main aim of this study is to compare the absolute spontaneous Raman scattering efficiency in CuAlS2 crystals with that of their isomorphous analog, zinc‐blende structure GaP crystals, known as one of the most efficient materials for Raman amplification. Observation of a high value of absolute scattering efficiency S/L dΩ (where S is the fraction of incident power that scatters into the solid angle d Ω and L is the optical path length with S/L dΩ=9.5×10−5 cm−1 sr−1), together with relatively narrow linewidth (Γ=5.1 cm−1, full width at half maximum at room temperature and Γ=1.5 cm−1 at 8 K for the strongest Γ1 phonon mode of CuAlS2 at 314 cm−1) indicate that CuAlS2 has the highest value of the stimulated Raman gain coefficient gs/I where I is the incident laser power density. The calculated value of this gain is gs/I=2.1×10−6 cm−1/W at 3...

Resonant inelastic light scattering and photoluminescence in isolated nc-Si/SiO2 quantum dots

Observation at the room temperature the spectra of the resonant inelastic light scattering by the spatially confined optical phonons as well as the excitonic luminescence caused by confinement effects in the ensemble of isolated quantum dots (QDs) nc-Si/SiO2 is reported. It is shown that the samples investigated are high purity and high crystalline perfection quality nc-Si/SiO2 QDs without amorphous phase α-Si and contaminants. Comparison between the experimental data obtained and phenomenological model of the strong space confinement of optical phonons revealed the need of the more accurate form of the weighted function for the confinement of optical phonons. It is shown that simultaneous detection of the inelastic light scattering by the confinement of phonons and the excitonic luminescence spectra by the confined electron-hole pairs in the nc-Si/SiO2 QDs allows selfconsistently to determine more accurate values of the diameter of the nc-Si/SiO2 QDs.

Acoustical plasma oscillations in photoexcited electron-hole plasma induced in GaAs layers embedded with InAs quantum dots

We present, to our knowledge, the first experimental evidence for the existence of acoustical plasma oscillations in photoexcited electron-hole plasma observed in resonant quasielastic electronic light scattering spectra in the near-infrared spectral range in a GaAs matrix embedded with self-assembled InAs quantum dots.

Determination of the hole concentration and mobility of p-GaP by Hall and by Raman measurements

Larger hole concentrations and lower mobilities are measured by Raman scattering of p-GaP in comparison with results of Hall and conductivity investigations. The Hall factor which is responsible for the differences can be obtained by these measurements and is discussed on the basis of a two-band model.

Detection of high-resolution Raman spectra in short oligonucleotides

High-resolution spectra of single-chain short oligonucleotides d(20G, 20T), where d is a deoxyribonucleoside, G is guanine, and T is thymine, have been obtained by the highly sensitive nonresonant Raman scattering method of biomacromolecules. In addition to their own multifunctional significance, short oligonucleotides attract interest as ideal model objects for revealing poorly studied peculiarities of tertiary and quaternary structures of DNA. The detection of narrow spectral lines has allowed determining the characteristic time scale and makes it possible to study the dynamics of fast relaxation processes of vibrational motions of atoms in biomacromolecules. It has been found that the FWHM of the narrowest 1355.4 cm−1 spectral line attributed to the vibrations of the dT methyl group is 14.6 cm−1. The corresponding lifetime is 0.38 ps.

Resonant Mandelstam-Brillouin light scattering and Raman scattering in semiconductors with intermediate exciton states belonging to discrete exciton bands and the continuous spectrum

The results of a theoretical and experimental investigation of resonant Mandelstam-Brillouin light scattering by thermal acoustic phonons with k=0 near the direct absorption edge (in the case of ZnSe crystals) are analyzed. The appearance of a new type of resonant increase in the intensity of Raman scattering by optical phonons with k≠0, which corresponds to resonance with the scattered light in the output channel, near the indirect absorption edge (in the case of semi-insulating GaP:N crystals) is also reported. The resonant gain reaches ∼4×103 at frequencies corresponding to overtone scattering assisted by LO(X) and LO(L) phonons. Exciton states belonging to both discrete exciton bands and to the continuous spectrum are considered as the intermediate states involved in the scattering processes in calculations of the resonant scattering tensors. In addition, all the intraband transitions, as well as the interband transitions between the conduction band, the valence bands, and the spin-orbit split-off band are taken into account, and good agreement with the experimental results is obtained.

High-resolution Raman scattering in oligonucleotides

High-resolution Raman spectra have been obtained by a high-sensitivity nonresonant scattering technique for short single-strand oligonucleotides synthesized by the solid-state amidophosphite method on an automated synthesizer.

Quasielastic scattering of light by a photoexcited electron-hole plasma induced in a GaAs layer in the presence of InAs quantum dots

The development of a method for registering quasielastic electronic light scattering spectra in the near-IR region, which makes it possible to detect light scattering by a photoexcited electron-hole plasma induced in a GaAs layer in the presence of a self-organized ensemble of InAs quantum dots, is reported. A substantial resonance intensification of such scattering, two orders of magnitude greater than the values established for the bulk material, is observed, and the main mechanism of such scattering is determined.

Observation of raman scattering by localized optical phonons bound to neutral donors in GaP:Si

Abstract Raman scattering by localized optical phonons bound to neutral donors with degenerate ground state has been observed in GaP:Si. The scattering efficiency was measured at T=6.0±0.1 K as a function of the net donor concentration ND-NA ranging from 1.6 ·1017 to 7.1· 1017 cm-3. It is found that reasonable agreement with the theory of weakly coupled electron-phonon modes obtained if a Bohr radius of a 0 =5.4 A is used, whereas a 0 =7.5 A is obtained in the hydrogenic effective-mass approximation using the ionization energy ED=86.7 meV.

Resonant raman scattering in complexes of nc-Si/SiO2 quantum dots and oligonucleotides

We report on the functionalization of nanocrystalline nc-Si/SiO2 semiconductor quantum dots (QDs) by short d(20G, 20T) oligonucleotides. The obtained complexes have been studied by Raman spectroscopy techniques with high spectral and spatial resolution. A new phenomenon of multiband resonant light scattering on single oligonucleotide molecules has been discovered, and peculiarities of this effect related to the nonradiative transfer of photoexcitation from nc-Si/SiO2 quantum dots to d(20G, 20T) oligonucleotide molecules have been revealed.