Enhanced reflection chiroptical effect of planar anisotropic chiral metamaterials placed on the interface of two media
Xiu Yang(杨秀)1, Tao Wei(魏涛)2, Feiliang Chen(陈飞良)3, Fuhua Gao(高福华)1,4, Jinglei Du(杜惊雷)1,4,†, and Yidong Hou(侯宜栋)1,‡
1College of Physics, Sichuan University, Chengdu 610065, China 2School of Medical Information Engineering, Jining Medical University, Jining 272067, China 3Microsystem & Terahertz Research Center of CAEP, China Academy of Engineering Physics, Chengdu 610299, China 4High Energy Density Physics of the Ministry of Education Key Laboratory, Sichuan University, Chengdu 610064, China
The strong chiroptical effect is highly desirable and has a wide range of applications in biosensing, chiral catalysis, polarization tuning, and chiral photo detection. In this work, we find a simple method to enhance the reflection circular dichroism (CDR) by placing the planar anisotropic chiral metamaterials (i.e., Z-shaped PACMs) on the interface of two media (i.e., Z-PCMI) with a large refractive index difference. The maximum reflection CDR from the complex system can reach about 0.840 when the refractive index is set as ntop = 4.0 and nbottom = 1.49, which is approximately three times larger than that of placing the Z-shaped PACMs directly on the substrate (i.e., Z-PCMS). While the minimum reflection CDR is 0.157 when the refractive index is set as nbottom = 1.49. So we can get a large available range of reflection CDR from –0.840 to –0.157. Meanwhile, the transmission CDT remains unchanged with the refractive index ntop increment. Our in-depth research indicates that the large reflection CDR is derived from the difference of non-conversion components of the planar anisotropic chiral metamaterials’ reflection matrices. In short, we provide a simple and practical method to enhance the chiroptical effect by changing the refractive index difference between two media without having to design a complex chiral structure.
* Project supported by the National Natural Science Foundation of China (Grant No. 11604227).
Cite this article:
Xiu Yang(杨秀), Tao Wei(魏涛), Feiliang Chen(陈飞良), Fuhua Gao(高福华), Jinglei Du(杜惊雷)†, and Yidong Hou(侯宜栋)‡ Enhanced reflection chiroptical effect of planar anisotropic chiral metamaterials placed on the interface of two media 2020 Chin. Phys. B 29 107303
Fig. 1.
Simulated reflection intensities of the Z-PCMI and Z-PCMS. (a) Schematic diagram of the Z-PCMI. The structure parameters are set as w1 = 115 nm, w2 = 85 nm, L1 = 125 nm, L2 = 105 nm, Px = 235 nm, and Py = 335 nm. The thickness h of the Z-shaped PACMs is 40 nm. (b) Schematic diagram of the Z-PCMS. (c)–(f) The simulated reflection intensities and CDR of the Z-PCMI and Z-PCMS, respectively.
Fig. 2.
The distribution of the electric field of the (a), (b) Z-PCMI and (c), (d) Z-PCMS at the resonant wavelengths of 1582 nm and 578 nm under the illumination of LCP and RCP.
Fig. 3.
The charge distribution of the (a), (b) Z-PCMI and (c), (d) Z-PCMS at the resonant wavelengths of 1582 nm and 578 nm under the illumination of the LCP and RCP.
Fig. 4.
The influence of the refractive index ntop on CD peaks. (a), (b) The reflection CDR and transmission CDT intensities of the Z-PCMI for the light illuminating along –Z direction. (c), (d) The reflection CDR and transmission CDT intensities of the Z-PCMI for the light illuminating along +Z direction.
Fig. 5.
(a), (c), (e) The reflection intensities and (b), (d), (f) transmission intensities of the Z-PCMI. The reflection and transmission intensities are obtained for the light illuminating along –Z direction.
Fig. 6.
The dispersion relation of the off-diagonal elements (rxy and ryx) of the linear reflection coefficients. (a)–(c) The linear polarization light illuminates the Z-PCMI along –Z direction. (d)–(f) The linear polarization light illuminates the Z-PCMI along +Z direction.
Fig. 7.
The reflection intensities of the G-PCMI and 卍-PCMI. (a) Schematic diagram of the G-PCMI, the structure parameters are set as W3 = 115 nm, L3 = 335 nm, Px = 235 nm, and Py = 335 nm. (b) Schematic diagram of the 卍-PCMI, the structure parameters are set as W4 = 50 nm, L4 = 250 nm, L5 = 125 nm, and Px = Py = 450 nm. The thickness h for both of the Ag-metal-grating and the 卍-shaped structures is 40 nm. The reflection intensities of (c), (e), (g) the G-PCMI; and (d), (f) (h) the 卍-PCMI. The refractive index ntop is increased from 1 to 4, while the refractive index nbottom keeps at 1.49.
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