Yu. M. Voronin

Effect of surface on phase modulation of light in a nematic layer

The nanorelief of orienting surfaces in a nematic layer is studied experimentally. The initial inclination angle of the director and the phase retardation of light in the crystal are determined, and the director reorientation dynamics in the crystal under SB deformation in an electric field is analyzed. It is shown that a thin layer of amorphous hydrogenated carbon (a-C: H) deposited on a GeO monoxide layer with an anisotropic nanorelief produced by the inclined deposition method smoothens the surface topography without changing the surface structure. Modification of the structure and physicochemical properties of the GeO surface alters the conditions of the anisotropic-elastic interaction at the interface with the liquid crystal, as evidenced by an increase in the S-effect threshold and a decrease in the initial inclination of the director from 22° (on the GeO surface) to 0–6°. Strong influence of the surface nanostructure on the dynamics of the director reorientation in the electric field and on the phase modulation of light is experimentally demonstrated. It is shown that the phase retardation of light in the GeO layer covered by an a-C: H film is twice as large as in the layer of the same thickness with a virgin surface.

Variations of the equilibrium make-up and spatial orientation of a molecular layer of polymethine dyes

Molecular layers of polymethine dyes on glass substrates have been investigated. As the surface concentration of molecules increases, the number of cis isomers of various structures decreases, and the relative concentration of all-trans isomers increases. The increased electron-donorability of the end groups and the lengthening of the conjugation chain increases the number of cis isomers of various structures. The equilibrium stereoisomer composition of the molecular layer is determined by the degree of asymmetry of the intramolecular electron-density distribution induced by its interaction with the substrate. A model is proposed for the reconstruction of the structure of the layer under the action of heating and photoexcitation. Reversible changes in the make-up of the layer are caused by stereoisomerization when a segment of a molecule rotates around the second bond of the conjugation chain; irreversible changes are caused by transformations in the asymmetry of the electron-density distribution in the molecule due to irreversible spatial reorientation of the components of the layer.

Luminescence video analyzer of biological microchips

This paper describes the operating principle of a luminescence video analyzer of biochips, based on a specially developed superbroad-band projection mirror-lens-prism objective. The video analyzer makes it possible to work with diagnostic tuberculosis chips. The field of view of the video analyzer is 6×8 mm, and the resolution over the field is better than 80 line/mm. The sensitivity is 10 amol of dye Cy5 per cell. The layout of the analyzer and a typical scanogram of the luminescence-signal distribution over the field of view are presented.

Limitation, switching, and radiation-flux modulation processes in nanocomposites based on carbon nanotubes

Laser-induced processes in the visible and near-IR regions have been investigated in organic nanocomposites based on carbon nanotubes. Bulk and thin-film organic structures, as well as nematic liquid-crystal mixtures, were chosen as test objects. A microscopic study of the test objects was carried out. It is established that the optical-limitation effect occurs in radiation at a wavelength of 1080 nm and that modulation and switching occur in the visible region at a wavelength of 633 nm. It is shown where these nanocomposites with carbon nanotubes fit in among other materials traditionally used in laser physics, nonlinear optics, and display engineering.