I. Yu. Denisyuk

Methods of generating superbroadband terahertz pulses with femtosecond lasers

This paper presents experimental results and an analysis of methods of generating terahertz (THz) radiation, using femtosecond laser sources: generation by photoconductive semiconductor antennas, nonlinear-optical generation of the difference frequency or optical rectification, and generation using optical breakdown in gases under the action of femtosecond pulses. An undoped semiconductor crystal of indium arsenide (InAs) located in a magnetic field, an electrooptic ZnTe crystal, an organic DAST crystal, and an optical spark in air were used as generators of THz radiation

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.

Polymer Composite Based on DAST Submicron Crystals: Technology and Properties

We propose a new nonlinear optical material, a polymeric nanocomposite based on DAST submicron crystals (trans-4’-(dimethylamino)-N-methyl-4-stilbazolium tosylate). The method and the preparation conditions for films based on a mixture of polymer solutions and a DAST powder are studied. Polymer matrices of various types, solvent ratio for the pair DAST/polymer, and electrical poling conditions are investigated. Absorption and luminescence spectra and the second harmonic generation have confirmed the creation of red-form DAST nanocrystals in polymer films. The figure of merit for a resulting polymer film is approximately 400 times higher than that for LiNbO3 at a wavelength of 1.32 microns.

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.

Obtaining terahertz-range metamaterials by laser engraving

This paper discusses the results of forming lattices of resonance and polarizing planar elements—metamaterials that serve the function of band-pass filters and polarizers of the terahertz range of wavelengths, made by the direct laser engraving of a metallized polymeric film. The excitation of a surface plasmon in a perforated metallic layer is investigated. Methods of calculating such structures are considered, the results of their experimental formation are presented, and the results of calculation and experiment are compared.

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.