![]() ![]() This relationship is fundamental for ghost imaging, and the quality of the reconstructed image depends on the choice of the radiation wavelength used to reconstruct the image of a particular object. It is also worth noting that in case of ghost imaging it is important to take into account the relationship between the characteristic values of the wavelengths in the selected pulse spectrum and the dimensions of the object. In this work, we use pulses with a spectral width of the order of 1 THz (from 0.2 to 1.2 THz). Thus, in contrast to standard optical bands, it is possible to work with THz pulses with a significant spectral width. Moreover, this model is capable of dealing with the broadband pulsed radiation. Current mathematical model can be used not only for radiation of the THz spectral range, but for any wavelength bands in wave optics and in radio physics as well. An opportunity of application of numerically formed speckle patterns for ghost image reconstruction even in case of working with broadband THz pulses is also shown. Furthermore, in the paper the possibility of utilizing THz speckle patterns in pseudothermal light ghost imaging algorithm was numerically demonstrated. Experimental verification of the formation of speckle patterns was carried out. Some limitations were shown that affect the size of speckle patterns formed by broadband THz radiation. ![]() Some of statistical characteristics of obtained speckle patterns, such as size and sharpness, and their dependencies on parameters of random phase screen are discussed. In this work we present a numerical model describing the formation of speckle patterns using broadband pulsed radiation of THz spectral range. This aspect motivated us to study speckle-pattern formation by broadband pulsed THz radiation. Producing of speckle patters for terahertz spectral range is of great interest to various applications related to terahertz imaging. A variant of amplitude modulation of probe radiation was proposed as a separate method for implementing THz imaging with sub-wavelength accuracy 36. This allows the ghost imaging technique in the THz range realization. The modified beam is directed to the crystal for generating the THz field. In this case, spatial light modulator, which modulate pump radiation is used. However, it should be noted that mask formation methods using nonlinear transformations in the crystal for generating the pulsed THz radiation exist and could be found in 35. The generation of speckle structures by pulsed THz radiation has not been studied yet. Usually, pulsed THz radiation has low energies 29, 30, but there are already widespread methods of generating high-energy radiation, for example, such as in organic crystals 31, 32 or by filamentation in gases or liquids 33, 34. High energies, various amplitude and phase objects transmission are the main advantages of monochromatic continuous THz radiation. In works 25, 26, 27, 28, the possibility of application such speckle structures for the ghost imaging technique was demonstrated. In this paper, for the formation of speckles, metal disk with a set of various random amplitude images around the disk circumference was used. The use of other sources of monochromatic radiation is presented in 28. In 25, 26, 27 formation of speckle patterns by reflection FEL THz radiation from a random rough surface was also considered. All these results were experimentally tested using a free electron laser (FEL). The first speckle structures in the THz region were first obtained using monochromatic continuous THz radiation and discussed in papers 24, 25. The formation of speckle patterns for THz radiation begins to be studied in detail only at the present time. In turn, terahertz (THz) radiation, due to the optical properties of various materials in this frequency range, as well as the features of individual properties of the radiation itself, is becoming more popular in quality control systems 10, 11, 12, safety 13, 14, 15, 16 and biomedicine application 17, 18, 19, communication 20, 21, 22, 23. optical coherence tomography and LIDAR technologies), there are fields in which usage of speckle patterns can be very promising: it applied for image retrieving in speckle metrology 3, single pixel imaging 4, for ghost imaging 5, 6, 7, 8, cryptography technique 9 etc. Despite the fact that the occurrence of speckle-noise can affect negatively for some imaging techniques (e. Speckle pattern formation is a phenomenon that occurs in situations where a coherent light reflects or transmits through a rough surface or a turbid medium 1, 2. ![]()
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