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This paper presents the results of 15 years of studies in the field of terahertz holography at the Novosibirsk free electron laser. They cover two areas: research on obtaining holographic images in the terahertz range and the use of diffractive optical elements to form high-power terahertz radiation fields with specified characteristics (intensity, phase, and polarization), using well-studied and widely applied in the optical range methods of optical (analog), digital, and computer-generated holography. All experiments were performed with the application of high-power coherent monochromatic frequency-tunable radiation from the Novosibirsk free electron laser. The features of hologram registration in the terahertz range are described. Methods, technologies, and optical materials for terahertz holographic elements are discussed. A wide range of promising applications of high-power terahertz fields with a given spatial structure is considered. The results of the study of terahertz holograms recorded as digital holograms, as well as radiation-resistive optical elements realized as computer-synthesized holograms, are presented.

The present paper is devoted to the actual problem of photonic crystal (PhC) logic gate design. The development of components for photonic digital computing systems will provide opportunities for high-efficient information processing. The use of 2D photonic crystals is one of the most promising approaches to designing interference logic gates. Photonic crystal band gap and use of lattice defects are giving opportunities for flexible control of waveguiding light. Interference logic gates of NOT, OR, AND, and XOR types based on the Y-shaped structure are well known. However, known realizations have limited energy efficiency. Earlier, a method for minimizing energy losses at the PhC waveguide bending based on genetic optimization of the PhC waveguide topology was proposed and investigated. In this paper, the genetic algorithm for optimization of the PhC interference logic gate of the NOT type was used. Optimization of the Y-shaped topology allowed for an increase in the energy efficiency of the logic gate to 95%. A description of the developed numerical procedure as well as computer simulation results are presented. The developed procedure includes the possibility of taking into account the limitations of the technology to be used for the realization of a designed 2D PhC structure.

We report an ultra-sensitive broadband photodetector based on horizontally aligned titanium disulfide nanosheets (TNs). Firstly, TNs were synthesized using the chemical vapor transport (CVT) technique to develop the photodetector, and then as-prepared TNs were deposited horizontally aligned between the interdigitated electrodes (IDEs) using the dielectrophoresis (DEP) technique. The photodetection performance of the as-prepared photodetector was analysed by illuminating the device with different wavelength low-power LED lights. The sensitivity of the as-developed photodetector has been studied for varying wavelength range (375 nm, 405 nm, 455 nm, 617 nm, 855 nm, 1050 nm) as well as for different power densities of individual incident lights. The as-developed photodetector shows high photoresponse for all mentioned wavelengths and shows a rapid response (10s) and recovery (10s) with ultra-high responsivity (1.174 × 104 AW−1), quantum efficiency (3.20 × 104 AW−1nm−1) as well as detectivity (3.039 × 1011 Jones) for 455 nm wavelength and 0.086 mW/mm2 power density of incident light. The ON/OFF ratio of the as-developed photodetector is found ultra-high i.e. 28.54. Its performance with respect to external bias voltage has also been studied and reported in the manuscript. The as-prepared TNs based photodetector shows many advantageous features like high stability and repeatability. The demonstrated ultra-sensitive photoresponse of as-prepared photodetector suggests the effectiveness of TNs for improving the characteristics of modern optoelectronic devices.

The characteristics of high-power vortex Bessel beams in the terahertz range (λ=141 μm) obtained with the use of diffractive axicons (DAs) illuminated by a Gaussian beam of the Novosibirsk free-electron laser were studied. Two of the three possible types of DA recently described in our previous paper, namely, binary spiral silicon axicons (BAs), forming beams with a topological charge l equal to 0–4 and 9, and a diamond “holographic” axicon (HA), forming a beam with l=9, were used in the experiments. These axicons formed beams whose cross sections in the region of inner Bessel rings were close to those of ideal Bessel beams, but their intensities varied in azimuth with a frequency of l and 2l for the BAs and HA, respectively. However, in the case of the BAs, the beams had a pronounced helical structure at the periphery, whereas for the HA, the beam was axisymmetric. By focusing these beams with a lens, we studied the structure of the so-called “perfect” beams (PBs). While an ideal Bessel beam exhibits a PB as a thin ring, in the case of the BAs, we observed a broadened ring structure consisting of 2l short spirals, and for the HA, we observed a narrow ring with 2l maxima in azimuth. A comparison of the numerical calculations and experiments showed that the observed azimuthal intensity variations can be attributed to inaccuracies in the preparation of the axicon relief and/or discrepancies between the calculated and actual wavelengths, within a few percent. The results of this work enable the establishment of quality requirements for axicon manufacture and the appropriate selection of the axicon type in accordance with the requirements for the beam.

Photodetectors that can operate over a wide range of temperatures, from cryogenic to elevated temperatures, are crucial for a variety of modern scientific fields, including aerospace, high-energy science, and astro-particle science. In this study, we investigate the temperature-dependent photodetection properties of titanium trisulfide (TiS3)- in order to develop high-performance photodetectors that can operate across a wide range of temperatures (77 K–543 K). We fabricate a solid-state photodetector using the dielectrophoresis technique, which demonstrates a quick response (response/recovery time ~0.093 s) and high performance over a wide range of temperatures. Specifically, the photodetector exhibits a very high photocurrent (6.95 × 10−5 A), photoresponsivity (1.624 × 108 A/W), quantum efficiency (3.3 × 108 A/W·nm), and detectivity (4.328 × 1015 Jones) for a 617 nm wavelength of light with a very weak intensity (~1.0 × 10−5 W/cm2). The developed photodetector also shows a very high device ON/OFF ratio (~32). Prior to fabrication, the TiS3 nanoribbons were synthesized using the chemical vapor technique and characterized according to their morphology, structure, stability, and electronic and optoelectronic properties; this was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and a UV–Visible–NIR spectrophotometer. We anticipate that this novel solid-state photodetector will have broad applications in modern optoelectronic devices.

Two-dimensional TiS3-nanostructures have been used to successfully remove toxic-industrial pollutants such as methyl-orange(MO) and methyl-blue(MB) from water bodies. Two-dimensional TiS3-nanostructures with exceptional mobility properties have been produced using the chemical vapor transport(CVT) technique and its photocatalytic capabilities are examined for potential environmental applications.Under infrared(IR) irradiation, the produced TiS3-nanoribbons were evaluated for their ability to degrade MO and MB solutions. TiS3-nanoribbons reveal significant high disintegration percentage; it is capable to decompose 90.3% of 50 μM MO pollutant solution in 5 min. Moreover it decomposes 94.4% of 50 μM MO solution as well as 10 μM MB solution in 20 min and 12 min, respectively.

Coherent terahertz beams with radial polarization of the 1st, 2nd, and 3rd orders have been generated with the use of silicon subwavelength diffractive optical elements (DOEs). Silicon elements were fabricated by a technology similar to the technology used before for the fabrication of DOEs forming laser terahertz beams with pre-given mode content. The beam of the terahertz Novosibirsk Free Electron Laser was used as the illuminating beam. The experimental results are in good agreement with the results of the computer simulation.

Three optical systems employing diffractive optical elements to generate surface plasmon polaritons (SPP) with orbital angular momentum on axisymmetric conductors are considered. In all three systems, the incident radiation is first converted by binary spiral phase axicons into a set of plane waves converging to the optical axis. In the zone of intersection of these waves, a "twisted" Bessel beam is formed. By fitting the diameter of the first ring of the Bessel beam to the diameter of the cylindrical conductor, it is possible to generate a rotating SPP by the "end-fire coupling" method. The use of an additional lens makes it possible to convert the SPP-exciting Bessel beam into a vortex annular beam whose diameter is independent of the topological charge of the beam. In the third scheme, converging plane waves are “intercepted” by a cylindrical metal diffraction grating, which forms twisted SPPs on a cylindrical conductor connected to the grating. Examples of the possible use of the proposed systems in experiments on a terahertz free electron laser are presented.

The paper is devoted to investigation of forming multimode coherent beams of terahertz radiation with pre-given transverse mode content and terahertz vector beams by use of silicon diffractive optical elements forming single modes from terahertz free-electron laser illuminating beam.

In this paper, we present the work of designing and fabricating a new generation of microelectromechanical systems (MEMS) based microfluidic preconcentrators (MFP) for volatile organic compounds (VOCs) quantification. The main objective of this work is to quantify the n-pentane impurities using MFP for sample preparation. The MFP was analyzed using Hewlett-Packard 5890 gas chromatography, having a flame ionization detector under isothermal conditions. The proposed MFP system includes two-microfluidic preconcentrators for continuous action and a system of four 3/2 solenoid valves with a control unit. Microfluidic preconcentrators were placed on metal plates and have circular channels filled with Al2O3 (50 μm), n-octane ResSil-C (80/100 mesh) sorbents of one nature and are hyphenated with the Peltier elements to regulate the temperature of sorption and desorption. The n-pentane quantitative determination was carried out using a calibration plot of gas mixtures on a successive dilution with the nitrogen. This study shows that the microfluidic preconcentrator system with Al2O3 and n-Octane ResSil-C sorbent concentrates the n-pentane traces up to 41 to 47 times from the gas mixture with the standard deviation of ≤5%. It has been observed that the n-octane ResSil-C based MFC shows very fast response (

A silicon subwavelengh terahertz axicon has been designed, fabricated, and investigated by methods of numerical and optical experiments. The research has been performed on a free-electron laser workstation NOVOFEL (Budker Institute of Nuclear Physics of SB RAS, Novosibirsk). Diffractive and polarization features of realized element have been investigated.

A method of high-frequency laser ablation using a two-coordinate beam scanner for the fabrication of a diffractive element of terahertz range with a continuous profile has been developed and successfully applied. Results of the characterization of the fabricated microrelief of a silicon focuser of a Gaussian beam into a square region are presented.