Yu. É. Burunkova

Microelements with High Aspect Ratio Prepared by Self-Focusing of Light at UV-Curing

The results of deep lithography based on the long-wavelength UV photopolymerization with a light self-focusing effect are presented. The effect of the formation of “bridges” between the nearest photopolymerization areas is revealed. Its sources such as the inhibition of photopolymerization by oxygen due to its diffusion to the exposed area are discussed. The conditions for a high aspect ratio of microelements (up to 100) are determined.

Nanomodified optical acrylate composites

This paper discusses the nanomodification of UV-hardenable acrylic composites when a low-molecular-weight ZnO nanoadditive is introduced and describes how this affects the optical and strength properties and the moisture absorption. Anomalous lowering of the moisture capacity by more than a factor of 5 is detected when 10% nanoparticles are introduced into the composite, while its strength is maintained. The internal structure and surface of the resulting nanocomposites are investigated by atomic-force microscopy.

An electro-optic polymer modulator for radio photonics

A method for developing an electro-optic polymer Mach‒Zehnder modulator based on polymethylmethacrylate- disperse red copolymer has been investigated. The inverse scheme is chosen as the basis for preparing a microstrip structure. This scheme entails the formation of microgrooves in the lower cladding layer by combining photolithography and reactive-ion etching (RIE), with subsequent deposition of an active electro-optic layer by centrifugation. The processes of forming layers and electrodes, the interaction between layers, the light transmission through the microstrip structure, and the modulator characteristics are considered.

Structural self-organization mechanism of ZnO nanoparticles in acrylate composites

Transparent homogeneous polymeric composite media have been obtained and investigated that contain up to 14 wt. % of ZnO nanoparticles. It has been established that the physical properties of the material, such as light scattering, Brinell hardness, and moisture absorption, vary nonmonotonically as the concentration of nanoparticles increases as a result of the modification of the internal structure of the nanocomposites. The nanocomposite structure has been investigated by the methods of IR spectroscopy and atomic-force microscopy. By comparison with the unmodified polymeric matrix, the hardness is not degraded, while the light scattering and moisture absorption are reduced. Because the active groups of one of the monomers (the carboxyl groups) interact with the surface of the nanoparticles, the latter are uniformly distributed over the entire volume of the material, and this forms an optically homogeneous nanocomposite medium. The ZnO nanoparticles are photocatalysts and centers of the polymerization process.

Polymeric electrooptic composite based on Disperse Red and its derivatives for use in photonics

Electrooptic polymers based on the chromophore Disperse Red and its derivatives in a matrix of polymethyl methacrylate and polyacrylate have been studied, and the limiting concentration of the chromophore has been determined. The optimum conditions have been found for creating anisotropy of the active layer by the method of polarization in a corona discharge. The degree of orientation of the chromophore and the temporal stability of the induced anisotropy have been investigated by measuring the optical absorption and the second-harmonic generation. Using the nanoimprint process, microstrip structures have been fabricated with a strip width of 5-50μm.

The formation of microstructures as a result of the self-focusing of light in a photopolymer nanocomposite

This paper presents the results of studies of the process of forming microstructures in UV-hardenable monomeric composites. The main effects that determine the parameters of the resulting structures are investigated: the self-focusing of light in a material with a positive sign of the refractive-index change during photopolymerization, shrinkage during photopolymerization, and the photoradical-diffusion rate. The conditions are determined for obtaining microstructures with a format ratio up to 1:50.

Formation of microstructures based on UV-hardenable acrylates

This paper discusses the possibilities of obtaining optical microstructures based on UV-hardenable acrylates. The applicability of the method of halftone lithography for obtaining polymeric microlenses and for forming microelements on the end of an optical fiber is investigated.

Electrooptic materials based on thin films of molecular crystals: Advantages and utilization prospects

This paper presents a review of foreign papers of recent years on new electrooptic molecular crystals. It is shown that they are promising for electrooptic devices of submillimeter range because of their unique combination of high electrooptic sensitivity (up to 700 pm/V) with low permittivity (5.2). Results of experiments done by the authors to obtain oriented single-crystal films of nonlinear-optical molecular crystals of DAST with a thickness of several microns and flat single crystals are presented. The nonlinear-optical parameters are confirmed by experiment from the generation of the second harmonic in the crystals. The luminescence spectra of all the resulting crystals are measured, and they confirm the existence of the dye that appears in the crystalline phase.

Synthesizing erbium and ytterbium oxide nanoparticles and obtaining luminescent polymeric composites based on them

This paper presents the results of a study of methods of synthesizing erbium and ytterbium oxide nanoparticles, formed on the surface of silicon nanoparticles by low- and high-temperature methods of synthesis. The technology thus developed is based on a method for obtaining nanoparticles of the rare-earth elements by thermally decomposing their salts in a medium of polyhydric alcohols at a temperature above the boiling point of water, allowing oxide nanoparticles to be obtained with no impurity in hydrate form. This method makes it possible to carry out nonaqueous synthesis at temperatures no higher than 250°C, and this maintains the nanoparticles at their original size without agglomeration. When the resulting nanoparticles were introduced into a photopolymerizable monomeric composite, a transparent nanocomposite material was obtained that could be used to form integrated-optics erbium amplifiers.

Features of the optical and nonlinear-optical characteristics of multilayer DAST crystals

This paper discusses the luminescence, the features, and the nonlinear conversion efficiency of optical radiation into the second harmonic as a function of the polarization direction of light in multilayer crystals of DAST [trans-4′-(dimethylamino)-N-methyl-4-stilbazolium tosylate], obtained by growth from a supersaturated solution in methanol.