Research on terahertz real-time near-field spectral imaging

In this paper, a real-time near-field high-resolution THz (terahertz, THz) spectral imaging system is designed and built by using optical rectification and wave-front tilting to generate strong-field terahertz signals and based on electro-optical detection. The system can switch between large beam THz imaging and tight-focusing THz imaging, which provides a method for implementing the integrated application of the system. Since the imaging is based on the traditional THz time-domain spectroscopy method, the spectral amplitude and phase information of the sample can be obtained simultaneously. The spectral resolution is about 15 GHz. A series of micromachining samples is measured and studied by using the system, and the performance of the imaging system is analyzed by using the micron structure. The results show the superiority of the real-time high-resolution terahertz spectral imaging system in terms of spatial resolution and imaging speed. The real-time imaging frame rate is up to 20 f/s (1200 frames/min) at 1024 pixel × 512 pixel. In the large-field THz imaging, the optimal spatial resolution reaches λ/4 at 1.5 THz. In the tightly focused THz imaging, the optimal spatial resolution reaches λ/12 at 0.82 THz. These properties make the system suitable for the applications in biomedical imaging, bbological effects and other areas .