Multi-frequency focusing of microjets generated by polygonal prisms  

作　　者：Yu-Jing Yang De-Long Zhang Ping-Rang Hua 杨育静;张德龙;华平壤(School of Precision Instruments and Opto-electronics Engineering,and Key Laboratory of Optoelectronic Information Science&Technology(Ministry of Education),Tianjin University,Tianjin 300072,China)

机构地区：[1]School of Precision Instruments and Opto-electronics Engineering,and Key Laboratory of Optoelectronic Information Science&Technology(Ministry of Education),Tianjin University,Tianjin 300072,China

出　　处：《Chinese Physics B》2022年第3期248-258,共11页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China (Grant No. 61875148)。

摘　　要：We systematically investigate the power distribution characteristics of microjets generated by prismatic scatterers with different shapes at sub-THz region(λ = 8.57 mm). Among these prismatic scatterers, the hexagonal-type one shows better focusing feature than the others. Aiming at the hexagonal-type one, we propose a double-layer scatterer composed of a Teflon hexagonal prism as an outer layer and a semiconductor cuboid as an inner layer. Aiming at the double-layer scatterer, we further study the effects of refractive index, size, and shape of the inner cuboid on microjet’s features. The study allows us to present an optimized double-layer scatterer, which has a side length λ/2(λ) and a refractive index 2.0(1.4) for the inner(outer) layer. We show that the optimized scatterer can produce an ultra-strong, ultra-narrow microjet with a power enhancement of;0 and a full width at half maximum(FWHM) of;0.26λ, and the microjet is just located at the output face. The microjet keeps compact within the distance range of λ from the output face. These features and effects are explained from the viewpoint of ray optics theory. According to the optimized double-layer scatterer, we further study the multi-frequency focusing features of the microjets, and find that the microjet remains good features at harmonic frequencies 2f_(0) and 3f_(0). In addition, we investigate the effect of an Au sphere presence in the center of the microjet on the power distribution. The results show that a spherical dark spot with a size similar to that of the Au sphere emerges in the area where the Au sphere is placed. The feature can be used to measure the size of a metallic particle.

关 键 词：photonic microjet hexagonal prism harmonical frequencies localized surface plasmon resonance 

分 类 号：O431.1[机械工程—光学工程]