Analogous to microsphere optical nanoscope, an easy and low-price method of THz imaging is proposed and developed for improving the spatial resolution beyond the diffraction limit. By attaching a 2-4 mm diameter Teflon sphere, a narrow, high-intensity, subdiffraction-waist THz beam with a strong jet-like distribution propagates into the background medium from the sphere’s shadow-side surface and a subwavelength spatial resolution better than λ/3 is demonstrated. Furthermore, the dielectric sphere-coupled THz microscope not only enables far-field, large-area measurement but also characterizes high-throughput and broad-band imaging properties. In addition, the size effect on terajet of dielectric sphere was simulated and shows that its magnification capability and focal length are size-dependent and frequencysensitive.
In this work, we demonstrate a high-selectivity terahertz (THz) band-stop filter with a wide range of center wavelengths (CWLs) from 150 to 600 μm (2.0 THz to 0.5 THz). The dip transmission is lower than 10 % at the center CWLs, even to 5 % at 1.9 THz. The band-stop terahertz filter is based on periodic metallic Cross Cell (CC) structures deposited on the top of a 50 μm thick polyimide film (Kapton) with low absorption and good mechanical properties, resulting in a large-area, freestanding and flexible membrane with a low intrinsic loss. The excellent tunable terahertz band-stop filter properties are investigated using terahertz time-domain spectroscopy. The measured and simulated results are coming to an excellent agreement. The THz band-stop filter possesses not only a light weight and polarization insensitivity but also a simple structure and high integration.
By using of high-resolution Terahertz time-domain spectroscopy, we show that both the fundamental and higher-order
Mie resonances can be excited in both magnetic and electric modes with in the one-dimensional dielectric grating.
Furthermore, their highly sensitive capability dependent on the frequency red-shift, line broadening, and transmission
decreasing were investigated with increasing refractive index and absorption strength of the surrounding media.
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