Giant third-harmonic in porous silicon photonic crystals and microcavities

A giant enhancement (no less than by 10³) of the optical third-harmonic generation in one-dimensional porous silicon microcavities and photonic crystals was observed experimentally. The enhancement is due to the resonant enhancement of the fundamental field in the cavity mode and the fulfillment of the phase matching condition at the photonic band gap edges of the photonic crystal and in the vicinity of the microcavity mode.     

Second-harmonic spectroscopy of electronic structure of Si/SiO2 multiple quantum wells

Size effects in the resonant nonlinear optical response of amorphous Si/SiO₂ multiple quantum wells (MQW) are studied by second-harmonic generation (SHG) spectroscopy in a spectral interval of second-harmonic photon energies from 2.5 to 3.4 eV. The sensitivity of SHG spectroscopy to thickness-dependent electronic structure (sub-band energy position and density of states line shape) of MQW is demonstrated. A monotonic red shift of central energies of SHG resonances by 120 m eV upon increase of the well thickness from 2.5 to 10 ? is observed. This is interpreted as a size dependence of the position of singularities in the combined density of states for a 2D gas of electrons moving in an effective potential well. It is shown that, for agreement with experiment, the simplest (rectangular) shape of the well should be modified in order to take into account the lattice-potential distortion at the interfaces. Received: 16 October 2001 / Revised version: 16 April 2002 / Published online: 6 June 2002     

Reaction of 1-substituted tetrahydro-β-carbolines with activated alkynes-a new original approach to the synthesis of tetrahydroazocino[5,4-<Emphasis Type="Italic">b</Emphasis>]indoles

The transformations of 1-substituted tetrahydro-β-carbolines by the action of activated alkynes were studied. The action of dimethyl acetylenedicarboxylate in methanol gives products of the opening of the tetrahydropyridine fragment, namely, 2-methoxyalkylindoles. The action of ethyl propiolate in ethanol and of tosylacetylene in methanol gives mixtures of azocino[5,4-b]indoles and 2-alkoxyindoles. The action of ethyl propiolate in acetonitrile gives azocinoindoles. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 703–715, May, 2007.     

Second harmonic generation induced by mechanical stresses in silicon

The optical second-harmonic generation induced by the external mechanical tension of the (001 ) silicon surface has been detected. A change in the spectrum of the second harmonic, which is caused by the modification of the band structure of silicon near the critical points E’_o and E₁ under mechanical tension, has been observed. The direct contribution to the optical second harmonic from changes in the band structure of silicon under tension is experimentally separated from the electric-field-induced co ntribution associated with the redistribution of the surface charge under the action of mechanical stresses.     

Pulsed electric stimulation as a method for assessing the quality of biological objects

By using new computer measurement system that allows you to create conditions for reversible depolarization of cell membranes, we investigated the correlation instantly values active and capacitive components with quality indicators of muscle tissue. Electrical test of objects is represented as a large array of data. Found that individual features of the muscle tissue, depending on the species, are impact on the array. When subsequently his compared with a unique array of references, it becomes possible to express and reliable assessment of the type of muscle tissue.     

Preparation method for noble metal-polymer matrix nanocomposites

A method is described for the preparation of new nanocomposites based on poly(ethylene terephthalate), poly(vinyl chloride), and polypropylene on the one hand and on noble metals (Ag and Pt) on the other. The method comprises the formation of nanoporous polymer matrices by crazing the polymers with simultaneous incorporation of noble metal precursors (AgNO₃ or H₂PtCl₆) into the matrices. Subsequent in situ reduction of the precursors yields the metal-polymer nanocomposites. Prospects for the practical application of the developed method for the production of metal-polymer nanocomposites are discussed.