| Terahertz imaging,one of the key technologies of terahertz,has important applications in the security,non-destructive testing,etc.The imaging resolution of typical terahertz time-domain spectral imaging system is about hundreds of micron due to the terahertz diffraction spot and hard to using in sub-wavelength imaging.While the near-field imaging is sort of the methods to break through the diffraction limit and could obtain super-resolution imaging.In this research,the system of terahertz super-resolution imaging based on femtosecond laser filamentation was designed,one imaging software was completed based on the Labview language.This software had achieved the control of the electric translation stage,the calculation of terahertz spectroscopy,the extraction and imaging of terahertz feature data,the imaging data storage and retrieval based on Sqlsever.One comparative study of the plasma filament formed via the lens in different positions truncated by 1000 mm and 400 mm focal length was completed.According to the influence of cutting off plasma filament formed by femtosecond laser on terahertz,the stability of terahertz time-domain amplitude and terahertz frequency-domain peak frequency generated by filament formed by two-color femtosecond laser via lens with longer focal length is lower than that of through lens with shorter focal length,especially the terahertz amplitude at the end scope of filament.A mask plate was scanned with THz wave(peak frequency 0.64 THz,wavelength 480 ?m)generated by femtosecond laser filament.The imaging resolution is achieved less than 100 ?m which is less than half of the incident wavelength,so the experimental results realized the THz super-resolution imaging.When demonstrating the distribution of mask structure,Time domain imaging is better than frequency-domain imaging and the integral energy imaging in time domain imaging can identify more fine structures of the mask plate and achieve better imaging results. |
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