Chiral metamaterials have stronger optical activity than natural materials within the terahertz frequencies, so they have attracted more attention. By arranging special silicon structures at terahertz frequencies, we propose an all-silicon-based extrinsic chirality structure with high outer circular dichroism in this paper. And its circular birefringence is also better than average. The properties of our all-silicon-based metamaterials are generated due to the resonance between the circularly polarized incident wave and the special silicon structure of the surface. The circular dichroism of the device due to transmission can reach 0.54. And we obtained the maximum polarization rotation angle can achieve 50°. In addition, the chirality of the device can be dynamically changed between 0.63THz-0.79THz. Such control can be achieved merely by changing the incident tilt angle. Our research can be applied to terahertz circular polarizer and polarimeter, which has great potential in optical path construction, light detection, signal transmission and processing.
Based on the influence of surface metal materials on electric field, a terahertz metamaterial absorber with a highly symmetrical open box was designed. Aiming at the traditional square ring absorber, the absorber is made of three open square rings and a pair of symmetrical strips of silicon. Starting from the structure and material of the absorber, the absorption rate of the absorber to the three-frequency band wave is regulated by changing the size of the surface metal ring, changing the thickness of the dielectric layer, changing the dielectric constant of the dielectric layer material, and adjusting the conductivity of the silicon material after the addition of semiconductor silicon. When no semiconductor silicon is added, the absorption rate of the absorber in the low frequency band reaches 94.77% and the absorption frequency band is 0.73thz. By increasing the thickness of dielectric layer, the phenomenon of redshift is obvious, which can realize the purpose of continuous frequency band absorption. By adding the silicon strip with symmetrical structure and changing the conductivity comparison, it is found that it can close the absorption peak in the high frequency band, reducing the absorption rate to less than %, and at the same time affecting the absorption rate of the low frequency band.
Real-time detection for living cells in vitro is essential for cell physiology, leading to a strong requirement of low cost and label free biosensors. At present, the terahertz plasmonic metamaterials (TPMMs) are an especially attractive application for biosensing owing to their sharp resonances respond. Compared with traditional biosensors, such as flow cytomertry, the TPMMs biosensors have many unique advantages, containing real-time monitoring, free label and high sensitivity. In this paper, we proposed a TPMMs which is designed by digging out periodically arranged regular hexagonal holes on the metal plate with the thickness of 200 nm. The samples of the TPMMs is used as a platform for detecting liver cancer cell GEP2 concentration at five levels (1 × 104, 5 × 104, 1 × 105, 3 × 105 and 5 × 105cells/ml). The results show that The THz PMMs biosensor cannot distinguish cell concentrations within the orders of magnitude between 1 × 104 and 5 × 104 cells/ml, however, it can distinguish cell concentrations within the orders of magnitude between 1 × 104 and 1 × 105 cells/ml based on the x-polarized reflection spectrum TPMMs biosensor. On the other hand, the transmission spectrum TPMMs biosensor has a significant detectability of the orders of magnitude cell concentration between 104 and 105 cells/ml. The proposed TPMMs biosensor paves a fascinating platform for have been widely applied for cell detection, biotechnology.
Laser shock microforming of Aluminum(Al) foil through fs laser has been researched in this paper. The influences
of confining layer, clamping method and impact times on induced dent depths were investigated experimentally.
Microstructure of fs laser shock forming Al foil was observed through Transmission electron microscopy (TEM). Under
the condition of tightly clamping, the dent depths increase with impact times and finally tend to saturating. Another new
confining layer, the main component of which is polypropylene, was applied and the confining effect of it is better
because of its higher impedance. TEM results show that dislocation is one of the main deformation mechanisms of fs
laser shock forming Al foil. Specially, most of dislocations exist in the form of short and discrete dislocation lines.
Parallel straight dislocation slip line also were observed. We analyzed that these unique dislocation arrangements are
due to fs laser-induced ultra high strain rate.
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