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Journals >Chinese Optics Letters >Volume 21 >Issue 1 >Page 013601 > Article

Chinese Optics Letters
Vol. 21, Issue 1, 013601 (2023)

Generation of tunable superchiral spot in metal-insulator-metal waveguide

Tao Zhuang¹, Haifeng Hu^{1、2、3、*}, and Qiwen Zhan^{1、2、3、**}

Author Affiliations

¹School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China

²Zhangjiang Laboratory, Shanghai 201204, China

³Shanghai Key Laboratory of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China

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DOI: 10.3788/COL202321.013601 Cite this Article Set citation alerts

Tao Zhuang, Haifeng Hu, Qiwen Zhan. Generation of tunable superchiral spot in metal-insulator-metal waveguide[J]. Chinese Optics Letters, 2023, 21(1): 013601 Copy Citation Text

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Abstract

The chiral feature of an optical field can be evaluated by the parameter of

g

-factor enhancement, which is helpful to enhance chiroptic signals from a chiral dipole. In this work, the superchiral spot has been theoretically proposed in metal-insulator-metal waveguides. The

g

-factor enhancement of the superchiral spot can be enhanced by 67-fold more than that of circularly polarized light, and the spot is confined in the deep wavelength scale along each spatial dimension. Moreover, the position of the superchiral spot can be tuned by manipulating the incident field. The tunable superchiral spot may find applications in chiral imaging and sensing.

Keywords

circular dichroism metal-insulator-metal waveguide radially polarized beam superchiral spot

C = \frac{ε_{0}}{2} \bar{E} \cdot \nabla \times \bar{E} + \frac{1}{2 µ_{0}} \bar{B} \cdot \nabla \times \bar{B},

(1)

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g = \frac{Im (G)}{Im (µ_{E})} \cdot \frac{2 C}{ω U_{e}} .

(2)

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g / g_{CPL} = \frac{Im (E \cdot H^{*})}{(1 / Z_{0}) {| E |}^{2}} .

(3)

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[\begin{matrix} E^{(ϕ)} (x, y, z) \\ H^{(ϕ)} (x, y, z) \end{matrix}] = a (ϕ) [\begin{matrix} e_{0} (z) \\ h_{0} (z) \end{matrix}] \exp (i β \hat{s} \cdot r_{∥}) .

(4)

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[\begin{matrix} E \\ H \end{matrix}] = \int_{0}^{2 π} [\begin{matrix} e_{0} (z) \\ h_{0} (z) \end{matrix}] \exp (i β \hat{s} \cdot r_{∥} \pm i ϕ) d ϕ .

(5)

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E_{ρ} = \pm π [J_{2} (β r) - J_{0} (β r)] e^{\pm i φ} e_{s 0} (z),

(6a)

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E_{ϕ} = - π i [J_{2} (β r) + J_{0} (β r)] e^{\pm i φ} e_{s 0} (z),

(6b)

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E_{z} = \pm 2 π i J_{1} (β r) e^{\pm i φ} e_{z} (z),

(6c)

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H_{ρ} = π i [J_{2} (β r) + J_{0} (β r)] e^{\pm i φ} h_{ϕ 0} (z),

(6d)

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H_{ϕ} = \pm π [J_{2} (β r) - J_{0} (β r)] e^{\pm i φ} h_{ϕ 0} (z),

(6e)

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[E, H] = {\begin{matrix} [E_{inc}^{(1)}, H_{inc}^{(1)}] + [E_{r}^{(1)}, H_{r}^{(1)}] & z < z_{1} \\ [E_{f}^{(2)}, H_{f}^{(2)}] + [E_{b}^{(2)}, H_{b}^{(2)}] & z_{1} < z < z_{2} \\ [E_{f}^{(3)}, H_{f}^{(3)}] + [E_{b}^{(3)}, H_{b}^{(3)}] & z_{2} < z < z_{3} \\ [E_{t}^{(4)}, H_{t}^{(4)}] & z > z_{3} \end{matrix} .

(7)

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E_{inc, ρ}^{(1)} = \frac{i A}{2} e^{i m φ} \int_{θ_{\min}}^{θ_{\max}} P (θ) e^{i k_{1} z \cos θ} \sin θ \cos θ [J_{m + 1} (x) - J_{m - 1} (x)] d θ,

(8a)

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E_{inc, φ}^{(1)} = \frac{A}{2} e^{i m φ} \int_{θ_{\min}}^{θ_{\max}} P (θ) e^{i k_{1} z \cos θ} \sin θ \cos θ [J_{m + 1} (x) + J_{m - 1} (x)] d θ,

(8b)

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E_{inc, z}^{(1)} = - A e^{i m φ} \int_{θ_{\min}}^{θ_{\max}} P (θ) e^{i k_{1} z \cos θ} \sin^{2} θ J_{m} (x) d θ,

(8c)

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H_{inc, ρ}^{(1)} = - \frac{A}{2 Z_{1}} e^{i m φ} \int_{θ_{\min}}^{θ_{\max}} P (θ) e^{i k_{1} z \cos θ} \sin θ [J_{m + 1} (x) + J_{m - 1} (x)] d θ,

(8d)

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H_{inc, φ}^{(1)} = \frac{i A}{2 Z_{1}} e^{i m φ} \int_{θ_{\min}}^{θ_{\max}} P (θ) e^{i k_{1} z \cos θ} \sin θ [J_{m + 1} (x) - J_{m - 1} (x)] d θ .

(8e)

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P (θ) = \sqrt{\cos θ} \exp [- β_{0}^{2} {(\frac{\sin θ}{\sin θ_{NA}})}^{2}] J_{1} (2 β_{0} \frac{\sin θ}{\sin θ_{NA}}),

(9)

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Tao Zhuang, Haifeng Hu, Qiwen Zhan. Generation of tunable superchiral spot in metal-insulator-metal waveguide[J]. Chinese Optics Letters, 2023, 21(1): 013601

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