Circular dichroism (CD) is useful in molecular chemistry, pharmaceuticals, and bio-sensing. In this paper, twisted Z-shaped nanostructure (TZN) is proposed to achieve giant CD. The TZN is composed of three vertical and twisted nanorods. Given that the resonance of vertical nanorod is only observable for left circularly polarized light excitation but is subdued for right circularly polarized light excitation, which leads to the giant CD effect approaching 88%. The subdued resonance of vertical nanorod can be excited by rotating the bottom nanorod. The CD properties can be tuned by the length of nanorods and the gap between them. These results would guide the design of plasmonic chiral nanostructures for achieving giant CD effect.
One of the key factors for solving the problems of re-entry communication interruption is electromagnetic (EM) wave transmission characteristics in a plasma. Theoretical and experimental studies were carried out on specific transmission characteristics for different plasma sheath characteristic under thin sheath condition in re-entry state. The paper presents systematic studies on the variations of wave attenuation characteristics versus plasma sheath thickness L, collision frequency ν, electron density n e and wave working frequency f in a φ 800 mm high temperature shock tube. In experiments, L is set to 4 cm and 38 cm. ν is 2 GHz and 15 GHz. n e is from 1×10 10 cm −3to 1×10 13 cm −3 , and f is set to 2, 5, 10, 14.6 GHz, respectively. Meanwhile, Wentzel-Kramers-Brillouin (WKB) and finite-difference time-domain (FDTD) methods are adopted to carry out theoretical simulation for comparison with experimental results. It is found that when L is much larger than EM wavelength λ (thick sheath) and ν is large, the theoretical result is in good agreement with experimental one, when sheath thickness L is much larger than λ, while ν is relatively small, two theoretical results are obviously different from the experimental ones. It means that the existing theoretical model can not fully describe the contribution of ν. Furthermore, when L and λ are of the same order of magnitude (thin sheath), the experimental result is much smaller than the theoretical values, which indicates that the current model can not properly describe the thin sheath effect on EM attenuation characteristics.
This paper presents the electromagnetic wave propagation characteristics in plasma and the attenuation coefficients of the microwave in terms of the parameters n~, v, w, L, cab. The r mm high temperature shock tube has been used to produce a uniform plasma. In order to get the attenuation of the electromagnetic wave through the plasma behind a shock wave, the microwave transmission has been used to measure the relative change of the wave power. The working frequency is f = (2 ~ 35) GHz (ca = 27r f, wave length A = 15 cm ~ 8 mm). The electron density in the plasma is nr = (3 x 10 l~ ~ 1 x 1014 )cm -3. The collision frequency v ----(1 x l0 s ~ 6 • 101~ )Hz. The thickness of the plasma layer L -----(2 ,.~ 80) cm. The electron circular frequency cab = eBo/m~, magnetic flux density B0 = (0 ~ 0.84)T. The experimental results show that when the plasma layer is thick (such as L/A >_ 10), the correlation between the attenuation coefficients of the electromagnetic waves and the parameters he, v, ca, L determined from the measurements are in good agreement with the theoretical predictions of electromagnetic wave propagations in the uniform infinite plasma. When the plasma layer is thin (such as when both L and A are of the same order), the theoretical results are only in a qualitative agreement with the experimental observations in the present parameter range, but the formula of the electromagnetic wave propagation theory in an uniform infinite plasma can not be used for quantitative computations of the correlation between the attenuation coefficients and the parameters n~, v, ca, L. In fact, if ca < cap, v 2 << ca2, the power attenuations K of the electromagnetic waves obtained from the measurements in the thin-layer plasma are much smaller than those of the theoretical predictions. On the other hand, if ca > cap, v 2 << w 2 (just v ..~ f), the measurements are much larger than the theoretical results. Also, we have measured the electromagnetic wave power attenuation value under the magnetic field and without a magnetic field. The result indicates that the value measured under the magnetic field shows a distinct improvement.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.