Low-potential anhydrous electrochemistry is an extremely effective method for the preparation of high-quality few-layer phosphorene in high yield.

Time-resolved terahertz spectroscopy has become a common method both for fundamental and applied studies focused on improving the quality of human life. However, the issue of finding materials applicable in these systems is still relevant. One of the appropriate solution is 2D materials. Here, we demonstrate the transmission properties of unique graphene-based structures with iron trichloride FeCl 3 dopant on glass, sapphire and Kapton polyimide film substrates that previously were not investigated in the framework of the above-described problems in near infrared and THz ranges. We also show properties of a thin tungsten disulfide WS 2 film fabricated from liquid crystal solutions transferred to a polyimide and polyethylene terephthalate substrates. The introduction of impurities, the selection of structural dimensions and the use of an appropriate substrate for modified 2D layered materials allow to control the transmission of samples for both the terahertz and infrared ranges, which can be used for creation of effective modulators and components for THz spectroscopy systems. Electronic supplementary material The online version of this article (10.1186/s11671-019-3062-3) contains supplementary material, which is available to authorized users.

The state-of-art broadband THz sources can contribute to the development of short-range 6G communications. this paper has demonstrated the feasibility of forming the controllable sequence of tHz subpulses in the temporal domain and the corresponding quasidiscrete spectrum by the interference of two tHz pulses with an exponential chirp. Moreover, due to small time delay between these pulses the temporal and spectral structures are similar to each other (so-called "linkage relation"). This will benefit information encoding in the THz range. The calculated metrics for the prototype communication channel based on the proposed method are competitive with existing short-range tHz cW channels. The maturity and commercialization of the fifth generation (5G) has already arrived 1. 6G (6th generation wireless systems)-a technology that supposed 100 to 1000 times 2,3 faster than 5G, is considered to come to our lives in the next ten years 4. Fresh spectral bands as well as advanced physical layer solutions are required for future wireless communications and THz wireless technology is a potential candidate 5-9. Usually optical frequency combs are used in IR optical communication systems providing high data rates for long distances 10. In this case, a large number of channels can be created using spectrum-sliced supercontinuum (SSSC) by arranging the interference of the two pulses with ultra-broadband spectra 11,12. In the THz range a typical method to generate THz spectral comb is THz generator pumped by a pulse train of fs laser pulses 13. It has also been reported that the transmitted spectrum of a THz pulse through a multilayer filter could achieve sub-comb structure 14. As a THz frequency comb, it can be used to measure the frequency of a continuous-wave THz with high precision 15 ; is suitable for the source of THz wireless communication of wavelength division multiplexing 16 , and expected to be used in ultra-fast information transmission systems 17. The use of pulsed THz sources is limited by strong free space losses due to the wide spectrum which does not overlap with atmospheric transparency window 18. Therefore, THz links have been suggested to use pulsed sources for short distance indoor communications 19,20 , and to use continuous radiation sources for long distances 21,22. The implementation of these techniques relies on ultra-fast modulation as well as encoding and decoding methods of THz wave, in which pulsed broadband THz technologies can make contributions 23. In the case of pulsed broadband radiation, the main aim is to create encoding methods based on wavelength division multiplexing (WDM). For instance, quasi-discrete THz supercontinuum, obtained via spectral interference of two THz pulses, can be used to achieve a data transfer rate of 34.1 Gb/s with 31 THz spectral lines 24. In the NIR region, the profiling of the spectral structure and the corresponding pulse sequence with a THz repetition rate has been verified both experimentally and analytically 25-27. The peculiarity of this approach lies in the fa...

This work contains results from studying the electro-optical properties of bulk and few-layered Van der Waals materials including intercalated graphene, phosphorene, and tungsten disulfide thin films. Different production methods and substrates are considered. The objective of the research is to assess the relevance of application of these materials in terahertz (THz) time-domain spectroscopy (TDS). Therefore, the study is conducted in the visible, NIR (near-infrared) and THz frequency ranges as the most critically in need of research when searching for effective materials for TDS.

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The dependences of the refractive index of a congruent LiNbO3 crystal cut perpendicular to the x and z axes on the radiation frequency in the range of 0.25–1.25 THz are presented. These dependences are presented for different values of the crystal thickness - 0.52 mm, 1 mm and 2.21 mm. A comparative analysis of the obtained dispersion curves with the results from other works is presented. The comparison was carried out by estimating the dispersion broadening of a THz pulse with time in the process of simulating its propagation in a medium with a given dispersion. It is shown that a 1.5-cycle THz pulse is broadened in media with dispersions found in other works, which does not correspond to experimental data. In accordance with this, it was concluded that the dispersion curves for congruent LiNbO3 from the considered works do not agree with the real values of the refractive index in the THz frequency range.

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