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Experimental results of the investigation of self-healing properties of terahertz Bessel beams with orbital angular momentum (OAM) with topological charges of l=3 and l=4 in free space after passing through a dispersive medium are presented.

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 feasibility of generating surface plasmon polaritons carrying orbital angular momentum ("vortex plasmons") on cylindrical conductors by an end-fire coupling technique in the spectral range from 8.5 to 141 μm (~ 2-40 THz) is considered. The front face of the cylinder is illuminated by Bessel beams formed using binary spiral phase axicons, or annual vortex beams formed in the focal plane of an additional lens. Graphs are constructed that reveal the relationship between the waveguide parameters (conductor diameter, which is equal to the diameter of the illuminating beam, and the “twist” angle of the plasmon) and the axicon parameters (the ratio of the axicon period to the radiation wavelength) for the above wavelengths and topological charges of the beams ranging from 1 to 9. The results obtained indicate the possibility of conducting experiments in the long-wavelength range for modeling a plasmon multiplex communication channel.

A review of experiments in the field of photonics and plasmonics, recently performed with the Novosibirsk free electron laser (NovoFEL) is given. Parameters of NovoFEL radiation and user workstations are described. Considerable attention was paid to the development and testing of quasi-optical elements designed for this range and to methods for the formation of powerful beams of terahertz radiation with a given mode composition. The use of terahertz radiation in the spectroscopy of gases and semiconductors, in generation and study of surface plasmon polaritons, as well as the use of the latter for the study of surfaces and in communication applications is described.

This review article deals with orientation controlled growth of Carbon Nanotubes (CNTs). Vertically aligned CNTs (VACNTs) are considered as the best type of CNTs among all known forms. The present article covered various aspects required for the successful growth of orientation controlled CNTs especially vertically aligned form. We discussed in details about the important properties of VACNTs and the importance of VACNTs in materials science with relative applications. It included different types of CVD techniques which support the vertically aligned CNTs growth on the substrate and also supports its mass production with proper growth mechanism. We made a detailed discussion about catalyst engineering and different type of carbon sources. The catalyst lifetime is a key factor for growing long CNTs, so, the reason of catalyst poisoning and the protection of catalyst from poisoning is also a part of our article. We also explained in detail about the types of catalyst protector elements with their suitability on different temperature as well for different gases used for continuous growth of VACNTs, yarns of CNTs as well as bulk production of CNTs. We covered a broad study about the various catalysts, catalyst thickness and catalyst deposition techniques. The suitable supporting layers for different catalysts with their impacts on morphology as well as on the structure of as grown CNTs are also discussed. For reducing cost of VACNTs production, we included eco-friendly natural wastage materials for catalysts and as carbon precursor. It also included the process by which different designs and structures of VACNTs can be made specifically by bending of VACNTs during growth running time through the utilization of different catalyst reservoirs. The discussion made in present article on the growth of oriented CNTs will help to grow selective vertically aligned CNTs in the convenient way with economical rate and thereby helps in the mass production of CNTs.

Surface plasmon polaritons (SPPs) carrying an orbital angular momentum were first obtained at a cylindrical brass-ZnS-air interface due to the diffraction of perfect vortex beams at the front end of a cylinder. The beams with a wavelength of 141 µm resulted from the transformation of a Gaussian beam of a free electron laser using a binary axicon and a lens. The propagation of rotating plasmons along an axisymmetric surface over a distance of 70 mm and their diffraction at the rear end of a cylindrical transmission line with conservation of the topological charge of the diffracted free wave were demonstrated.

A three-layer structure is fabricated on a low-resistance silicon substrate using plasma chemical etching. We study it experimentally and show that a substrate with such a structure can be used as an absorber of terahertz (THz) radiation in the frequency range of 0.5−2.0 THz. For this structure, absorbance in the indicated frequency range is measured to be more than 95%.

An increase in the radiation power of terahertz (THz) sources requires the development of new optics working with it. The laser-assisted replication technique is proposed to fabricate the diamond cylindrical diffractive lens with a continuous profile for the THz range. The procedure involves the inverted structuring of a silicon substrate by laser ablation for its further replication to the diamond surface utilizing the chemical vapor deposition process. Testing of the fabricated lens performed with a free-electron laser at the wavelength of 141 µm has demonstrated high diffraction efficiency ( 95 ± 5 % ) and a good agreement between the measured and expected intensity distribution in the focal plane.

In this article, we propose methods for the generation of surface plasmon polaritons (SPPs), both carrying orbital angular momentum, and conventional ones, using vortex Bessel beams, and also investigate the propagation of SPPs along flat and cylindrical conductors. The possibility of their practical application is discussed and the first experimental results are presented.

Diffractive optics technologies are opening up new possibilities for power terahertz laser radiation controlling. Silicon diffractive optical elements are used for focusing of a terahertz laser beam into pre-given domains, for forming beams with needed transverse mode content, as well as for terahertz beam polarization transforming.

Infrared detectors are the main component of remote controls, night vision cameras, non-contact thermometers and other similar devices today. Considering the wide range of primary radiation receivers practical applications, we have developed a highly sensitive IR-sensor based on reduced graphene oxide (rGO). This material is easy to fabricate and it has a moderate price in mass production. In addition, rGO has an insulating layer on its surface, which provides long-term stability of the sensor, because it is not affected by the environment composition. The developed IR-sensor has a linear response over the entire dynamic range. In the present work, the rGO film response in the form of a change in its resistance under the CO2-laser radiation exposure was experimentally investigated. The rGO-based sensitive element transient characteristics have been determined under the exposure of radiation at a wavelength of 10.6 μm.

Development of terahertz lasers determines actuality of research in the field of THz diffractive optics. Results and perspectives of THz diffractive optics application are considered.

Chemical detection of toxic gases, such as greenhouse gases is still very important as a research topic. To design gas sensor detectors based on single-walled carbon nanotubes (SWCNTs) with high sensitivity and selectivity for the toxic environment is a continuous process. The aim is to detect $${\hbox {NO}}_{2}$$ gas with better sensitivity. In the present work, the thin-film sensor is fabricated on $${\hbox {SiO}}_{2}$$ substrate and it is functionalized with polyethylenimine (PEI). It has been established that PEI functionalized SWCNTs (F-SWCNTs) show high sensitivity towards strong electron-withdrawing particles. It was found that at room temperature, SWCNTs-PEI functionalized gas sensor exhibited a higher sensitivity of 37.00% as compared with bare SWCNTs gas sensor. The gas sensor has shown the repeatable response for the entire concentration range studied. The sensing properties and the PEI functionalization duration effects on the behaviour of SWCNTs-based gas sensors were demonstrated. Figure (A) Micrograph of the PEI-functionalized SWCNT sensor, Figure (B) Change in the behaviour of the SWCNT sensor with the increment in functionalization duration, Figure (C) Repeatability of the SWCNT sensor, Figure (D) Response of the SWCNT sensor in the presence of various concentrationS of $${\hbox {NO}}_{2}$$ gases.

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.

With the development of technology, process control has become central to the working of modern industries as well as devices. Sensors are at the heart of these advances; where, the need for high sensitivity, quick response as well as recovery, and low power consumption is imperative at economic prices. The use of nanomaterials has shown to greatly enhance the sensing performance of a device owing to the large surface area of such materials. The large surface-to-volume and pitted structure, along with extraordinary electrical and thermal conductivities, make it most favorable material for gas sensing applications. Major advancements in the CNTs based gas sensors involve the enhancing the sensitivity and selectivity of the nanotubes. This can be achieved by specific functionalization of CNTs with a variety of materials such as noble metals, metal oxides, polymers, etc. It has been found that, for sensor applications, modifications of CNTs with certain materials can enhance the selectivity and sensitivity of CNTs and make it sensitive towards several harmful gases. In this article, we present a comprehensive analysis of the past as well as present day CNTs gas sensors technology. The study presented in this paper are helpful to develop advanced devices with the application of highly efficient sensors.

This article introduces sensing of nitrogen dioxide (NO2) gas using horizontally aligned single walled carbon nanotubes (SWCNTs) in between gold interdigitated electrodes (IDEs). The fabrication process employed microelectromechanical system (MEMS), photolithography, thin film metallization, and dielectrophoresis (DEP) methods. Gold IDEs were fabricated using photolithography and thin film metallization techniques onto SiSiO2 substrate, and then, SWCNTs were horizontally aligned in between IDE using DEP. The fabricated sensor was characterized for sensing of NO2 gas in the range 1 to 5 ppm. The cardinal sensing principle involves the reduction of NO2 molecules on interaction with horizontally aligned SWCNTs. This reduction of NO2 molecules is attributed to intratube and intertube electron modulation and charge transfer mechanisms on SWCNTs surface, which is manifested in terms of change in resistance of the SWCNTs. Therefore, change in resistance of SWCNTs on changing the concentration of NO2 gas was considered as the detection signal. The sensitivity of the present NO2 gas sensor is found to be 70, which is better than the reported ones. The additional advantages of present study are that it is highly efficient, portable, compact, and cost effective technique for sensing of NO2 gas, which possesses potential applications in environmental monitoring of NO 2 gas and space flight demonstration.

Green catalyst derived from plants, a cheap and abundant natural source, is used for the synthesis of multi-walled carbon nanotubes (MWNTs). The concept is unconventional and practically realized into existence by simple CVD growth while keeping away the potential hazards caused by metal catalyst on environment and living organisms. The notable points to mention of such growth are: (1) grown CNTs are free from toxic metal catalyst, (2) low growth temperature (575 °C) required and produced high yield vis-a-vis any other catalyst used so far reported, and (3) no need of expensive and complex systems for its synthesis. Besides, growth of SWNT as well as carbon nano-belts with hollow rectangular cross-section is observed when growth temperature increased to 800 °C, specifically, for the wall-nut extract. The samples were characterized by microscopic and spectroscopic analysis and the results verified our study. The present work provides innovative technique and may open up new avenues for CNTs synthesis and its applications.

The development and fabrication of broadband antireflection structures (ARS) for the THz frequency range are discussed. The three-level ARS was fabricated on a silicon substrate by RIE technology (Bosch-process). Results of realized ARS spectral investigation are presented.

The present paper is devoted to the use of transverse modes and beams with orbital angular momentum (OAM) for the development of THz multichannel systems using mode division multiplexing (MDM).

The propagation length of surface plasmon polaritons (SPPs) increases with wavelength, which makes it possible to use radiation from the far-infrared and terahertz ranges to create communication devices employing SPPs as carriers of information. In this paper, we consider methods for implementing the multiplex transmission of information along cylindrical conductors using a combination of SPPs with orbital angular momentum and present experimental setups for the experiments on the Novosibirsk free electron laser.

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.

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.

Mode spatial multiplexing has been shown for Gauss-Hermite and vortex beams in the THz spectral range. Transformation of a Gaussian TEM00 input beam of Novosibirsk Free Electron Laser was realized by silicon diffractive optical elements. Superposition of vortices with different topological charges has been examined A correlation filter was applied for mode analysis.

Titanium trisulfide(TiS3) is a newly emerging material of the transition-metal tri-chalcogenides(TMTCs) family. It has non-linear optical property and conductivity. In addition, the highly anisotropic electronic and thermal properties of TiS3 offer a new platform to the worldwide researchers to develop future electronics and optoelectronics devices. While bulk TiS3 has indirect bandgap, mono- and few-layered TiS3 is n-type semiconductor with a direct bandgap of 1.0 ± 0.1eV. This article deals with the controlled synthesis of TiS3 along with the analysis of their basic construction and electronic band structure. The manipulation of band structure by external forces, such as strain, temperature, etc., and the variation in electronic and optoelectronic properties of TiS3 with respect to band structure manipulation has also been investigated. The various vibrational modes involved in TiS3; the origin of vibrational modes and the effects of temperature, pressure and angle of polarized light on vibrational modes were analysed in detail. We review both experimental data as well as theoretical data about the thermal and electronics transport coefficients, thermoelectric property and the temperature induced charge density waves relative to TiS3. Finally, the electronic and optoelectronic applications of TiS3, such as FETs, p-n junction, linear and polarized-light photodetectors and mode-locked-lasers have been discussed.

A technique of high-frequency laser ablation using a 2D beam scanner has been designed and applied to creation of a silicon diffractive optical element (DOE) with a continuous profile to focus a terahertz Gaussian beam into a square region. The microrelief of the resulting silicon DOE has been analyzed with a white-light interferometer and a scanning electron microscope. The distribution of radiation behind the DOE illuminated by a high-power beam of the Novosibirsk free-electron laser at a wavelength of 130 µm, recorded with a pyroelectric camera, has been demonstrated. The measured diffraction efficiency of the DOE is equal to 97 ± 2 % .

The diffractive optical element (DOE) for transforming of linearly polarized THz radiation beam into a cylindrically polarized beam is investigated. Optimal diffractive microrelief height is determined by numerical simulation.

A transverse mode converter based on a binary microrelief implemented directly on the end-face of a few-mode fiber was numerically investigated. The results of numerical simulation demonstrated the converter to form LP-11 and LP-21 modes with high efficiency, providing a more-than 92 % mode purity. Transformations of modes excited by a fiber microbending were also numerically investigated. The excited beams were shown to save their mode purity even in a strong bending as the arising parasitical modes were mostly unguided by the fiber. The resulting beam power and mode content were also demonstrated to depend on the beam and bending mutual orientation for beams with strong rotational symmetry.

Single-walled carbon nanotubes (SWCNTs) were dispersed in an imidazolium-based ionic liquid (IL) and investigated in terms of structural quality, surface functionalization and inter-CNT force. Analysis by field emission electron microscopy and transmission electron microscopy shows the IL layer to coat the SWNTs, and FTIR and Raman spectroscopy confirm strong binding of the ILs to the SWNTs. Two kinds of resistive sensors were fabricated, one by drop casting of IL-wrapped SWCNTs, the other by conventional dispersion of SWCNTs. Good response and recovery to NO 2 is achieved with the IL-wrapped SWCNTs material upon UV-light exposure, which is needed because decrease the desorption energy barrier to increase the gas molecule desorption. NO 2 can be detected in the 1–20 ppm concentration range. The sensor is not interfered by humidity due to the hydrophobic tail of PF6 (ionic liquid) that makes our sensor highly resistant to moisture.

Present article deals with microsystem technology and nanosensors. We covered the properties and synthesis technology of Carbon Nanomaterials. The detailed discussion has been made on synthesis of Carbon Nanotubes by thermal chemical vapour deposition (CVD) while reduced graphene oxide by modified Hummers method. Further, as grown Carbon nanomaterials have been used for developing optical detector for visible to near infrared range and Nitrogen Dioxide gas sensor.

NO2, having a reddish-brown color and biting odor, is the most prominent toxic waste present in the atmosphere. The major contributors to NO2 gas include emissions from industrial and transport sectors. There are many porous nanostructures which have shown enormous potential for NO2 gas sensing. Among these, the first group comprises metal oxides while the second group includes two-dimensional transition metal dichalcogenides (2D TMDs). Besides, these materials have also been modified or functionalized with different metals for improving various sensing parameters such as selectivity, sensitivity, affordability, stability and life span of the device. In this article, we discuss new developments in the fields of metal oxide nanostructures and 2D TMDs for NO2 sensing. Additionally, a comparative analysis of different modifications and their effects on sensing properties of both the materials is presented.

Precise microstructuring of silicon with short laser pulses is a promising technique for fabrication of kinoform diffractive optical elements (DOEs) for high-power THz radiation. Micrometer-scale surface roughness being a typical result of the silicon microstructuring with laser is an important factor reducing optical performance of the fabricated DOEs. We demonstrate here that proper optimization of the processing conditions under profiling of high-resistance silicon surface by 1 ps laser pulses at λ = 1.03 μm allows formation of cylindrical Fresnel lens with the surface roughness of 0.5–1.2 µm being one order of magnitude smaller than reported earlier. Testing of the fabricated lens with a free electron laser at the wavelength of 141 μm has shown that the laser-machined silicon retains its original transmittance. Diffraction efficiency (0.93 ± 0.06) and deviation of the laser intensity profile in the lens focus from the theoretical expectations have been evaluated. Additionally, influence of the surface roughness on transmittance of the laser-machined silicon in the wavelength range of 95–400 μm was studied by means of time domain spectroscopy.

Vortex Bessel beams with topological charges $l=\pm 1$ and $l=\pm 2$ were generated with diffractive optical elements in the THz range using monochromatic and tunable radiation of the Novosibirsk free electron laser. Diffractive and interference techniques were applied to study the main characteristics of the vortex beams, i.e. topological charge and pitch-factor. Analytical studies, simulations and experimental results are given.

We study diffraction of Bessel vortex beams with topological charges of ±1 and ±2 and a wavelength of 130 µm on two-dimensional amplitude periodic gratings. Results of simulations and experiments at the Novosibirsk Free Electron Laser facility show that there appear periodic patterns in the planes corresponding to the classical main and fractional Talbot planes, but instead of self-images of the holes, there are observed periodic lattices of annular vortex microbeams with topological charges corresponding to the charge of the beam illuminating the grating. The ring diameters are the same for beams with different topological charges, but they are proportional to the grating period and inversely proportional to the diameter of the beam illuminating the grating.

Comparison of the two laser sources (UV nanosecond and IR femtosecond) used for the formation of micro-relief at the silicon surface showed the advantage of the second one. A four-level silicon diffractive THz Fresnel lens has been fabricated by laser ablation at high repetition rate (f = 200 kHz) of femtosecond Yb:YAG laser. Features of the lens were investigated in the beam of the Novosibirsk free electron laser at the wavelength of 141 μm. Detailed results of investigation of fabricated lens micro-relief are presented. The measured diffractive efficiency of the lens is in good agreement with the theoretical prediction.

This paper reports the design and fabrication of a 2-degree-of-freedom (DOF) decoupled vibratory gyroscope based on a silicon-on-insulator (SOI) MEMS process. The 2-DOF capacitive comb structure is deliberately designed to have a decoupled drive and sense mode oscillation to prevent the unstable operation due to mechanical coupling, resulting in a low zero rate out-put drift. It is well known that the closer are the drive and sense resonances, the higher is the angular rate resolution of the gyroscope. Generally, this is achieved by using symmetric suspensions, but it results in a reduced bandwidth. The proposed design has been configured to achieve a bandwidth of about 150 Hz, while ensuring the decoupled operation of the drive and sense modes. An analytical method has been employed to study the steady state response of the 2-DOF structure. FEM analysis has been carried out in CoventorWare® MEMS Design software and the simulation results show that the drive resonance occurs at 21.48 kHz and sense resonance at 21.63 kHz, which are in close agreement with the theoretical results. The structure is designed with a 15 µm thick device layer. Fabrication of the design is proposed using a two mask process based on Deep reactive-ion etching (DRIE) and sacrificial wet release etching on a SOI wafer. DRIE etching with an aspect ratio of 1:5 has been successfully carried out as desired and the results have been presented.

Recently, terahertz Bessel beams with angular orbital momentum (“vortex beams”) with topological charges l = ±1 and l = ±2 were generated for the first time using radiation of the Novosibirsk free electron laser (NovoFEL) and silicon binary phase axicons (Knyazev et al., Phys. Rev. Letters, vol. 115, Art. 163901, 2015). Such beams are prospective for application in wireless communication and remote sensing. In present paper, numerical modelling of generation and transformation of vortex beams based on the scalar diffraction theory has been performed. It was shown that the Bessel beams with the diameters of the first ring of 1.7 and 3.2 mm for topological charges ±1 and ±2, respectively, propagate at a distance up to 160 mm without dispersion. Calculation showed that the propagation distance can be increased by reducing of the radiation wavelength or using a telescopic system. In the first case, the propagation distance grows up inversely proportional to the wavelength, whereas, in the latter case the propagation distance increases as a square of a ratio of the telescope lenses foci. Modelling of the passing of the vortex Bessel beams through a random phase screen and amplitude obstacles showed the self-healing ability of the beams. Even if an obstacle with a diameter of 10 mm blocks several central rings of Bessel beam, it reconstructs itself after passing a length of about 100 mm. Results of the simulations are in a good agreement with the experimental data, when the latter exist.

The Novosibirsk free electron laser is the first multi-turn energy-recovery linear accelerator with three separate laser systems (the terahertz, far-infrared and mid-infrared ones). The facility is well equipped with optical elements and instrumentation available to Russian and foreign users. In this paper, we describe in brief the workstations of the facility and survey selected recent experiments using intense monochromatic terahertz laser radiation, which can be tuned from 90 to 240 μm.

We demonstrate results of studies of a silicon binary diffractive optical element (DOE) focusing a terahertz laser Gaussian beam into a paraxial segment. The characteristics of the DOE were examined on a Novosibirsk Free Electron Laser beam of 141-μm wavelength.

Carbon nanotubes (CNT) are one of the most promising materials for various applications. CNT have perfect mechanical and electrical properties, but they do not have the ability to react with most groups of chemical compounds. This is the reason why CNT still not using in the industry widely. The problem could be solved by modification of CNT lattice, which makes CNT more chemically reactive. This study reveals the potential methods of covalent functionalization of CNT with nitrogen-containing chemicals. Used methodology included chemical methods of grafting functional groups on defect-site of CNT and sidewall functionalization of CNT. Therefore, the resulting amide groups on the CNT surface will allow to use CNT in the manufacturing of polymers.

In this paper, we have performed experimental, analytical, and numerical studies of beams with topological charges of $\ifmmode\pm\else\textpm\fi{}1$ and $\ifmmode\pm\else\textpm\fi{}2$ formed by silicon binary phase axicons (BPAs) with spiral zone structures. The axicons were illuminated with the Novosibirsk free electron laser radiation (a continuous stream of 100-ps pulses at $f=5.6$ MHz). The cw power of the beams produced reached 30 W and can by doubled via antireflection coating of the axicons. The intensity distribution in the beam cross sections was in good agreement with the Bessel functions and was kept constant within a distance of about $L/r\ensuremath{\approx}190$ and 100, where the first ring radii of the beams r were 0.9 and 1.5 mm for the Bessel beams of the first and second orders, respectively. Although the characteristics of the beams (Bessel cross section, ``diffraction-free'' propagation, self-recovery after passing obstacles, and randomly inhomogeneous media) corresponded to the properties of ideal Bessel beams, their spatial Fourier spectrum (the image in the focal plane of the lens) was, instead of an ideal ring, intertwined segments of arcs with phases shifted by $\ensuremath{\pi}$, the number of which was equal to the double value of the topological charge. This feature can be used, for example, in a demultiplexing unit of a free vortex-wave communication system or for identification of beam topological charge. We also revisited Young's double-slit diffraction and rotation of beams obstructed by a half-plane, previously applied to Laguerre-Gaussian beam characterization, in the case of the Bessel beams. The Young diffraction pattern demonstrated in this case a complicated intensity-phase distribution. It was shown that the Bessel beams formed by BPAs have two important advantages, which can be used in applications, in comparison with other methods of generation, e.g., a combination of an axicon lens with a spiral phase plate. Although the phase jumps of the axicons are designed for a determined wavelength (141 $\ensuremath{\mu}\mathrm{m}$ in our case), the BPAs can form the beams at incident radiation with any wavelength, albeit with a reduced diffraction efficiency, and their cross section is the same for any wavelength.