Formation of gigahertz pulse train by chirped terahertz pulses interference

Abstract

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...

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