Ultra-compact high-sensitivity plasmonic sensor based on Fano resonance with symmetry breaking ring cavity

GuiQian Lin; GuiQian Lin; Hui Yang; Hui Yang; Yan Deng; Yan Deng; Dandan Wu; Xuan Zhou; Yunwen Wu; Guangtao Cao; Guangtao Cao; Jian Chen; Wanmei Sun; Renlong Zhou; Renlong Zhou

doi:10.1364/OE.27.033359

1. Introduction

Surface plasmon is a kind of surface evanescent wave produced by collective oscillation of free electrons on metal surface when matching the frequency of photons in incident light waves. The surface plasmon polaritons (SPPs) [1,2] bound to the metal-dielectric interface is a class of surface plasmon, which can overcome the classical diffraction limit [3] using deep sub-wavelength metal structures [4]. The rapid developments in nanotechnology and plasmonics facilitate the manipulation of light at the nanoscale, and plasmonic devices have been widely used in sensing [5–8], optical switching [9–11], filtering [12–16] and other fields [17–19].

As one of the most prevalent devices in optical circuits, the surface plasmon resonance (SPR) optical sensor based on metal-dielectric-metal (MDM) waveguide has attracted enormous attention due to small size, high sensitivity and easy integration [20,21]. Recent trends in plasmonic sensor research have advanced towards waveguide coupled resonator structures that enable some novel nonlinear optical effects, such as Fano resonance [22–27] and electromagnetic induced transparency [28–30]. For the Fano resonance arising from the interference of the radiant mode and subradiant mode in metallic nanostructures, it exhibits tremendous field enhancements [26]. The tremendous field enhancements are quite sensitive to the structural and electromagnetic parameters, empowering that a small variation can shift the Fano resonances significantly. Compared to the symmetric Lorentzian-like profile in the conventional resonance, Fano resonance exhibits obviously asymmetric spectral line shape [31] and large spectral contrasts.

Due to its tremendous field enhancements, sharp asymmetric spectral line shape, and large spectral contrasts, Fano resonance based on optical cavities has significant applications in sensing technology. In 2012, Lu et al. established a nanosensor in MDM waveguide-cavity system and obtained a figure of merit (FOM) of ∼500 [32]. Chen et al. demonstrated a novel and compact refractive index sensor based on Fano resonance which comprises with a stub and groove resonator coupled with a MDM waveguide [33]. In addition, Wen et al. proposed a plasmonic MDM waveguide structure by placing a slot cavity below or above a groove [34]. To obtain the asymmetric Fano resonance line shape, various artificial nanostructures have been proposed and designed recently. However, studies on Fano resonance emerged by a single symmetry breaking cavity are relatively rare.

Here, we numerically and analytically demonstrate high-sensitivity and tunable sensing performances based on Fano resonances in a plasmonic symmetry breaking cavity nanostructure. The proposed structure composed of MDM waveguide and a symmetry breaking ring cavity. The on-chip symmetry broken design provides a solution for ultra-compact plasmonic sensor. The proposed analytical theory is in good agreement with the finite-difference time-domain (FDTD) simulations, and the magnetic field distributions imply that Fano resonance line shapes arising from the interference between symmetry-mode and asymmetry-mode in symmetry-broken cavity. Moreover, the Fano peak intensity can be tuned by the degree of asymmetry of ring cavity, which lays the groundwork for improving the performances of plasmonic sensing.

2. Plasmonic structure and theoretical model

The nanoscale plasmonic sensor structure is schematically shown in Fig. 1(a). The plasmonic structure is comprised of two MDM waveguides coupled with a ring resonator, and a metal bar is positioned inside the ring cavity to break the symmetry of ring cavity. In Fig. 1(a), the width of waveguide is d, and the coupling distances between the two waveguides and ring cavity are both w. r denotes the radius of ring cavity, and r_m presents the radius of metal bar. The degree of asymmetry is denoted by the intersection angle θ between the metal bar and y-axis, and θ increases clockwise. For metal and dielectric materials in the structure, we select silver and air, respectively. In general, the Drude model is used to approximately describe the relative dielectric constant of silver by the equation: ɛ_m (ω) =ɛ_∞ - ω_p / (ω² + iωγ_p). ɛ_∞= 3.7 represents the dielectric constant of silver when the frequency is infinite, ω_p= 1.38×10¹⁶rad/s and γ_p= 2.37×10¹³rad/s represent the oscillation frequency and damping frequency of silver, respectively. The spectral responses are numerically studied by the two-dimensional FDTD method. The perfect matched layer (PML) boundary conditions are used in the FDTD simulations, and the source is Gaussian light, which is incident from the left waveguide. When the incident light is TM-polarized wave, the SPPs will be excited and confined in waveguide.

Fig. 1. Schematic of the plasmonic structure. (a) 3-dimensional structure. (b) Equivalent theoretical model for Fig. 1(a).

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To explain the physics of spectral responses in plasmonic structure, a theoretical model is established based on the coupled mode theory (CMT), as illustrated in Fig. 1(b). Then, the characteristic equations for the evolution of cavity modes can be expressed as follows

(1)$$\frac{\partial }{{\partial t}}|a \rangle ={-} i\Omega |a \rangle - {\Gamma _i}|a \rangle - {\Gamma _e}|a \rangle + {S_{ + in}}|{\textrm K} \rangle + {S_{ - in}}|{\textrm K} \rangle - i{\textrm M}|a \rangle ,$$

(2)$${S_{ + out}} ={-} {S_{ - in}} + \left\langle {{\textrm K}} | {a} \right\rangle ,$$

(3)$${S_{ - out}} ={-} {S_{ + in}} + \left\langle {{\textrm K}} | \right\rangle ,$$

where S_±in and S_±out represent the amplitudes of incoming and outgoing waves in waveguides. $|a \rangle$ and $|{\textrm K} \rangle$, respectively, stand for the field amplitude of resonant mode and coupling coefficient between resonator and waveguides. $\left\langle {\textrm K} \right|$ is dependent on $|{\textrm K} \rangle$. They can be written as

(4)$$|a \rangle = \left( {\begin{array}{c} {{a_1}}\\ {{a_2}}\\ \vdots \\ {{a_m}} \end{array}} \right),\textrm{ }|{\textrm K} \rangle = \left( {\begin{array}{c} {{\kappa_1}}\\ {{\kappa_2}}\\ \vdots \\ {{\kappa_m}} \end{array}} \right),\textrm{ }\left\langle K \right|= \left( {\begin{array}{cccc} {{\kappa_1}^\ast }&{{\kappa_2}^\ast }& \cdots &{{\kappa_m}^\ast } \end{array}} \right),$$

κ_m stands for the coupling between waveguides and cavity.

In Eq. (1), Ω, Γ_i, Γ_e and Μ matrices are expressed as

(5)$$\begin{array}{l} \Omega = \left( {\begin{array}{ccc} {{\omega_{11}}}& \ldots &{{\omega_{1m}}}\\ \vdots & \ddots & \vdots \\ {{\omega_{m1}}}& \cdots &{{\omega_{mm}}} \end{array}} \right),{\Gamma _i} = \left( {\begin{array}{ccc} {{\gamma_{i11}}}& \ldots &{{\gamma_{i1m}}}\\ \vdots & \ddots & \vdots \\ {{\gamma_{im1}}}& \cdots &{{\gamma_{imm}}} \end{array}} \right),\\ {\Gamma _e} = \left( {\begin{array}{ccc} {{\gamma_{e11}}}& \ldots &{{\gamma_{e1m}}}\\ \vdots & \ddots & \vdots \\ {{\gamma_{em1}}}& \cdots &{{\gamma_{emm}}} \end{array}} \right),{\textrm M} = \left( {\begin{array}{ccc} {{\mu_{11}}}& \ldots &{{\mu_{1m}}}\\ \vdots & \ddots & \vdots \\ {{\mu_{m1}}}& \cdots &{{\mu_{mm}}} \end{array}} \right). \end{array}$$

Ω, Γ_i, Γ_e and Μ matrices denote resonance frequencies, intrinsic loss rate, external loss rate of cavity, and coupling coefficients between resonant modes, respectively. In Ω, Γ_i, Γ_e and Μ matrices, if p ≠ q, ω_pq= 0, γ_ipq= 0, γ_epq= 0, and μ_pq= ω_qq / (2Q_pq); if p = q, ω_pq= ω_p, γ_ipq= ω_pq / (2Q_iq), γ_epq= ω_pq / (2Q_eq), and μ_pq= 0. The cavity quality factors Q_iq, Q_eq are related to intrinsic loss, waveguide coupling loss, respectively. Q_pq denotes the coupling between the pth and qth modes. Based on the condition S_-in= 0 and Eqs. (1)–(5), we can get the transmission efficiency of the system I = |S_+out / S_+in|².

When m = 2, the power transmission is given as

(6)$$I = {\left|{\frac{{\sqrt {\frac{1}{{{\tau_{\omega 1}}}}} ({D_2}\sqrt {\frac{1}{{{\tau_{\omega 1}}}}} ) - j{\mu_{12}}\sqrt {\frac{1}{{{\tau_{\omega 1}}}}} \sqrt {\frac{1}{{{\tau_{\omega 2}}}}} + \sqrt {\frac{1}{{{\tau_{\omega 2}}}}} ({D_1}\sqrt {\frac{1}{{{\tau_{\omega 2}}}}} ) - j{\mu_{21}}\sqrt {\frac{1}{{{\tau_{\omega 1}}}}} \sqrt {\frac{1}{{{\tau_{\omega 2}}}}} }}{{{D_1}{D_2} + {\mu_{12}}{\mu_{21}}}}} \right|^2}, $$

where D₁= -jω + jω₁ + 1/τ_i₁+ 1/τ_ω₁, D₂= -jω + jω₂ + 1/τ_i₂ + 1/τ_ω₂. In the proposed symmetry breaking ring cavity, supporting multiple modes, resonance modes are orthogonal to each other. Thus, the M matrix in Eq. (1) is equal to zero matrix in the following contents, and waveguide induces the indirect coupling between different resonant modes [35,36].

3. Results and discussion

Figures 2(a)–2(d) display the transmission spectrum and field distributions of the structure. The geometrical parameters of the plasmonic system are set as d = 50 nm, w = 10 nm, r = 200 nm, r_m= 15 nm, and θ = 0°. Figure 2(a) illustrates a Fano lineshape and a Lorentzian lineshape in transmission spectra. The Fano peak and Lorentzian peak occur at λ = 919 nm and λ = 1900nm, corresponding to the first (P1) and second (P2) resonant modes of ring resonator, respectively. The analytical result (red line) is in good agreement with the FDTD simulations (black line), which proves the correctness of the established theoretical model. In order to better understand the transmission characteristics of the structure, Figures 2(b)–2(d) show the contour profiles of the field |H_z| at different wavelengths. Figures 2(b) and 2(c) present the magnetic field |H_z| for the wavelengths of resonant peaks at P1 and P2, respectively. As illustrated, the magnetic field distributions exhibit two resonant modes in ring cavity, and the SPPs can pass through the right port. Figure 2(d) presents the magnetic field distribution at wavelength λ = 2200 nm. It is apparent that there is a very weak field distribution |H_z| in the ring cavity, and the transmittance approaches zero.

In Fig. 3(a), we present the transmission spectra with metal bar placed at θ = 0°, θ = 15°, θ = 45° and θ = 75°, respectively. Apparently, a sharp dip appears in the transmission peak with changing θ, and it can be seen that the Fano lineshape exhibits in the transmission spectra. To real the spectral responses in the plasmonic system, we study the spectral features by referring to the Fano formula [26]

(7)$$F(\lambda ) = {F_0}\frac{{{{[q + {{2 \times ({{2\pi c} \mathord{\left/ {\vphantom {{2\pi c} \lambda }} \right.} \lambda } - {{2\pi c} \mathord{\left/ {\vphantom {{2\pi c} {{\lambda_0}}}} \right.} {{\lambda _0}}})} \mathord{\left/ {\vphantom {{2 \times ({{2\pi c} \mathord{\left/ {\vphantom {{2\pi c} \lambda }} \right.} \lambda } - {{2\pi c} \mathord{\left/ {\vphantom {{2\pi c} {{\lambda_0}}}} \right.} {{\lambda_0}}})} \Gamma }} \right.} \Gamma }]}^2}}}{{1 + {{[{{2 \times ({{2\pi c} \mathord{\left/ {\vphantom {{2\pi c} \lambda }} \right.} \lambda } - {{2\pi c} \mathord{\left/ {\vphantom {{2\pi c} {{\lambda_0}}}} \right.} {{\lambda _0}}})} \mathord{\left/ {\vphantom {{2 \times ({{2\pi c} \mathord{\left/ {\vphantom {{2\pi c} \lambda }} \right.} \lambda } - {{2\pi c} \mathord{\left/ {\vphantom {{2\pi c} {{\lambda_0}}}} \right.} {{\lambda_0}}})} \Gamma }} \right.} \Gamma }]}^2}}} + A(\lambda ).$$

q denotes the so-called Fano parameter, which is related to the incident waves and geometric and material parameters of system. The spectral profile is dependent on q. F₀ denotes the amplitude of the Fano resonance. Γ is the resonance width. λ and c denote the wavelength and light velocity in vacuum, respectively. λ₀ is the resonant wavelength. A(λ) denotes the background term. Basing on Eq. (7), we can obtain the Fano parameter q for the spectral lineshape, which indicates the spectral features in the plasmonic system. For the Lorentzian lineshape, Fano parameter q → ±∞. Figure 3(b) presents the evolution of transmittance as function of θ and response wavelength, where θ varies from 0° to 360°. The Fano dip around P1 shifts from left to right of Fano peak, which leads to reciprocal transformation between Lorentzian and Fano lineshapes. The Fano dip around P2 is always on the left of Fano peak. Moreover, it is apparent that the transmission spectra vary periodically versus θ, and the periods around P1 and P2 are 90° and 180°, respectively.

Fig. 2. (a) The transmission spectrum of the structure with metal bar at θ = 0°. (b)–(d) Magnetic field distributions at wavelengths 919 nm, 1900nm, 2200 nm.

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Fig. 3. (a) The transmission spectra of the plasmonic structure at different θ. (b)Evolution of the transmittance versus θ. (c)–(e) show the magnetic field (H_z) distributions, with θ = 15°, for λ = 907 nm (left peak), λ = 921 nm (dip), λ = 939 nm (right peak), respectively.

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To get more insight into the spectral responses, Figures 3(c)–3(e) show the magnetic field distributions, corresponding to θ = 15°, at λ = 907 nm (left peak), λ = 921 nm (dip), λ = 939 nm (right peak). With respect to the x axis, the field distributions in Figs. 3(c) and 3(e) are symmetrical and asymmetrical, respectively. The field distribution in Fig. 3(d) is in conformity with the Fano dip in transmission spectrum. According to the distributions of magnetic field, the resonance modes in the proposed structure are classified as symmetric mode and asymmetric mode. Combining with the numerical simulations and theoretical analyses, we can conclude that both the Fano lineshape and Lorentzian lineshape result from the interference between two different pathways related to the symmetric and asymmetric modes. The Fano spectral responses originate from the symmetric and asymmetric modes with different resonant frequencies, while the Lorentzian spectral features are attributed to the symmetric and asymmetric modes with identical resonant frequencies. Thus, the symmetry breaking ring cavity can be used to drive new resonant modes as well as provide a promising approach to generate Fano resonance.

Compared with the Lorentzian spectral features, Fano resonance with sharp slope and asymmetrical line shape holds potential applications in nanoscale ultra-sensitive sensors. To illustrate the sensing characteristics of the plasmonic system, the transmission spectra versus refractive index n of surrounding medium are given in Fig. 4(a), where the refractive index n increases from 1.00 to 1.10 with step of 0.02. It can be observed from the Fig. 4 that the transmission spectra are related to the refractive index of surrounding medium, and the two Fano resonances (FR1 and FR2) exhibits monotonically red shift with increasing the refractive index. The FR2 shifts bigger, and the transmittances of Fano peaks decrease owning to the increase of transmission losses. According to Fig. 4(a), we display the linear relationship between the Fano peak wavelength and refractive index in Fig. 4(b). As the refractive index n varies from 1.00 to 1.10, the wavelength shift of FR1 (red dotted line) is 92 nm, while the wavelength shift of FR2 (blue dotted line) is 181 nm. Generally, the sensitivity of the plasmonic sensor is defined as dλ / dn. Then the sensitivity around FR1 and FR2 is, respectively, 920 nm/RIU and 1810nm/RIU. It is obvious that the sensitivity is proportional to the Fano resonance wavelength, which provides a way to improve the performance of optical sensors.

Fig. 4. (a) The transmission spectra versus the refractive index n with metal bar placed at θ = 75°. (b) Fano peak wavelengths versus refractive index n of the surrounding medium.

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In order to better characterize the performance of the plasmonic sensor, the limit of detection (LOD) and figure of merit (FOM) are key parameters. For a specific wavelength, the limit of detection is defined as [37]

(8)$$LOD = \frac{{0.02}}{S},$$

which reflects the detection capability of a sensor. Basing on Eq. (8), we obtain that the detection limit around FR1 equals 2.17×10⁻⁵RIU, and the detection limit around FR2 equals 1.1×10⁻⁵RIU.

In sensing system, the higher FOM indicates the better sensing performance, and the FOM could be expressed as FOM = |dI(n) / dn| at fixed wavelength [38]. dI(n) denotes the transmission intensity variation, and dn stands for the change of refractive index of the surrounding medium. As refractive index varies from 1.00 to 1.02, we plot the FOM, in Fig. 5(a), for the symmetry-broken ring cavity system with θ = 15°. It can be found that the maximum FOM approaches 34.4 at wavelength λ = 939.5nm. Figure 5(b) demonstrates the maximum value of FOM (MAX of FOM) around FR1 versus the position of metal bar θ, and the MAX of FOM reaches the maximum value at θ = 15°, which indicates that the position of metal bar provides an efficient way to modulate the sensing performance.

Fig. 5. (a) The FOM curve for the plasmonic symmetry-broken ring cavity system with θ = 15°. (b) The maximum value of FOM (MAX of FOM) around FR1 versus the position of metal bar θ. (c) The FOM curves for different ranges of refractive index with the metal bar at θ = 15°. (d) An enlarged view of the first Fano resonance. (e) The curves of FOM* for symmetrical cavity (blue line) and symmetry-breaking cavity (red line).

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Figure 5(c) displays the FOM as a function of the response wavelength for different refractive index n, where n varies from 1.00 to 1.10. In this case, the change of refractive index dn is 0.02, and dI(n) = I(1.02) - I(1.00), I(1.04) - I(1.02), I(1.06) - I(1.04), I(1.08) - I(1.06), I(1.10) - I(1.08), respectively. Figure 5(d) is an enlarged view around FR1 in Fig. 5(c). It illustrates that the maximum of FOM approaches 34.4 in range of 1.00-1.02. The FOM around FR1 is more than three times larger than that in [38]. Thus, the range of refractive index also has an impact on the maximum of FOM. To study the sensing performance of the plasmonic sensor, another figure of merit (FOM*) is defined as [39] FOM* = dI / Idn. As the refractive index increases from 1.00 to 1.02, Figure 5(e) shows the FOM* of symmetrical cavity and symmetry-breaking cavity systems. For symmetrical cavity without metal bar, the maximum of FOM* is about 103 at wavelength λ = 1900nm; for symmetry-breaking cavity with metal bar at θ = 75°, the maximum of FOM* could reach 1760 at wavelength λ = 919nm. The maximum of FOM* for the symmetry-breaking ring cavity structure is 17 times larger than that of the symmetrical ring cavity system. Thus, the symmetry breaking can improve the figure of merit for refractive index sensing. These results could lay a foundation for the ultra-compact and high-performance plasmonic sensors.

To our knowledge, the performance of the proposed refractive index sensor is better than previously reported plasmonic sensors [16,32,40–43]. Here, to characterize the sensing performance versus temperature, the ethanol is chosen as the filling medium in waveguides and ring cavity. The temperature coefficient of ethanol is 3.94×10⁻⁴, and the functional relation between refractive index and temperature can be defined as [44]

(9)$$n = 1.36048 - 3.94 \times {10^{ - 4}}(T - {T_0}), $$

where T₀ denotes the room temperature and its value is 20^○C, and T is the measured ambient temperature. The sensitivity of temperature sensor is defined as dλ / dT.

Figure 6(a) displays the transmission spectra versus different temperatures of ethanol, such as T = 80^○C, T = 60^○C, T = 20^○C, T = -20^○C, T = -60^○C, and T = -100^○C. It is clear that the Fano resonant wavelength decreases with the increase of temperature, and the overall spectral shape remains unchanged. Equation (9) indicates that the refractive index is linearly related to temperature, and Figure 4(b) shows that the Fano peak wavelength has a linear relationship with the refractive index. Thus, in Fig. 6(b), there is a linear variation of Fano peak wavelength with the measured temperature. When T rises from -100^○C to 80^○C, with the metal bar placed at θ = 75^○, the variations of wavelength of FR1 and FR2 are 63.13nm, 126.25nm, respectively. According to the definition of the sensitivity for the temperature sensor, the sensitivity around FR1 and FR2 approach 0.35nm/^○C and 0.701nm/^○C, respectively. As mentioned above, the symmetry breaking ring cavity structure filled with ethanol holds potential applications for the manufacture of on-chip temperature sensors.

Fig. 6. (a) The transmission spectrum versus the temperature of ethanol. (b)The wavelengths of Fano peaks versus the temperature of ethanol.

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4. Conclusion

In summary, we have reported a joint numerical and theoretical study on ultra-compact and high-sensitivity plasmonic sensor based on Fano resonance, which is composed of two waveguides coupling with a symmetry breaking ring resonator. The established theoretical model is validated by numerical simulations, and sets up a platform to understand the physics of Fano resonance. Differing with the coupled cavities, the Fano resonance originates from the interference between symmetry-mode and asymmetry-mode, and the Fano parameter q and sensing performance rely on the degree of asymmetry of the ring cavity. The sensitivity of the plasmonic sensor could approach 1810nm/RIU. In particular, the refractive index changes as small as 10⁻⁵ can be detected, and the FOM of symmetry-breaking cavity structure was 17 times larger than that of symmetry cavity system. Moreover, the plasmonic sensor can achieve high sensitivity to external temperature changes. This small footprint together with the tunable spectral responses can actualize active devices for fundamental study and applications in on-chip high-sensitivity sensors.

Funding

National Natural Science Foundation of China (11564014, 61865006); Natural Science Foundation of Hunan Province (2017JJ2097, 2019JJ50481); Education Department of Hunan Province (16A067, 18B324); Xiangxi Autonomous Prefecture Science and Technology Program (2018SF5024); Natural Science Foundation of Guangdong Province (2018A030313684); Major Projects of Guangdong Education Department for Foundation Research and Applied Research (2017KTSCX134).

References

1. I. Haddouche and L. Cherbi, “Comparison of finite element and transfer matrix methods for numerical investigation of surface plasmon waveguides,” Opt. Commun. 382, 132–137 (2017). [CrossRef]

2. W. L. Barnes, A. Dereux, and T. W. Ebbesen, “Surface plasmon subwavelength optics,” Nature 424(6950), 824–830 (2003). [CrossRef]

3. D. K. Gramotnev and S. I. Bozhevolnyi, “Plasmonics beyond the diffraction limit,” Nat. Photonics 4(2), 83–91 (2010). [CrossRef]

4. S. A. Maier, “Gain-assisted propagation of electromagnetic energy in subwavelength surface plasmon polariton gap waveguides,” Opt. Commun. 258(2), 295–299 (2006). [CrossRef]

5. G. N. Tsigaridas, “A study on refractive index sensors based on optical micro-ring resonators,” Photonic Sens. 7(3), 217–225 (2017). [CrossRef]

6. L. Xu, S. Wang, and L. Wu, “Refractive index sensing based on plasmonic waveguide side coupled with bilaterally located double cavities,” IEEE Trans. Nanotechnol. 13(5), 875–880 (2014). [CrossRef]

7. Z. He, H. Li, B. Li, Z. Chen, H. Xu, and M. Zheng, “Theoretical analysis of ultrahigh figure of merit sensing in plasmonic waveguides with a multimode stub,” Opt. Lett. 41(22), 5206–5209 (2016). [CrossRef]

8. L. Tong, H. Wei, S. Zhang, and H. Xu, “Recent advances in plasmonic sensors,” Sensors 14(5), 7959–7973 (2014). [CrossRef]

9. X. X. Niu, X. Y. Hu, Q. C. Yan, J. K. Zhu, H. T. Cheng, Y. F. Huang, C. C. Lu, Y. L. Fu, and Q. H. Gong, “Plasmon-induced transparency effect for ultracompact on-chip devices,” Nanophotonics 8(7), 1125–1149 (2019). [CrossRef]

10. C. G. Min and G. Veronis, “Asorption switches in metal-dielectric-metal plasmonic waveguides,” Opt. Express 17(13), 10757–10766 (2009). [CrossRef]

11. N. Nozhat and N. Granpayeh, “All-optical nonlinear plasmonic ring resonator switches,” J. Mod. Opt. 61(20), 1690–1695 (2014). [CrossRef]

12. S. Wang, L. Yan, Q. Xu, and S. Li, “A MIM filter based on a side-coupled crossbeam square-ring resonator,” Plasmonics 11(5), 1291–1296 (2016). [CrossRef]

13. F. S. Ma and C. Lee, “Optical nanofilters based on meta-atom side-coupled plasmonics metal-insulator-metal waveguides,” J. Lightwave Technol. 31(17), 2876–2880 (2013). [CrossRef]

14. G. Cao, H. Li, Y. Deng, S. Zhan, Z. He, and B. Li, “Systematic theoretical analysis of selective-mode plasmonic filter based on aperture-side-coupled slot cavity,” Plasmonics 9(5), 1163–1169 (2014). [CrossRef]

15. Z. Zhang, F. Shi, and Y. Chen, “Tunable multichannel plasmonic filter based on coupling-induced mode splitting,” Plasmonics 10(1), 139–144 (2015). [CrossRef]

16. C. X. Xiong, H. J. Li, H. Xu, M. Z. Zhao, B. H. Zhang, C. Liu, and K. Wu, “Coupling effects in single-mode and multimode resonator-coupled system,” Opt. Express 27(13), 17718–17728 (2019). [CrossRef]

17. B. Zhang, H. Li, H. Xu, M. Zhao, C. Xiong, C. Liu, and K. Wu, “Absorption and slow-light analysis based on tunable plasmon-induced transparency in patterned graphene metamaterial,” Opt. Express 27(3), 3598–3608 (2019). [CrossRef]

18. E. Gao, Z. Liu, H. Li, H. Xu, Z. Zhang, X. Luo, C. Xiong, C. Liu, B. Zhang, and F. Zhou, “Dynamically tunable dual plasmon-induced transparency and absorption based on a single-layer patterned graphene metamaterial,” Opt. Express 27(10), 13884–13894 (2019). [CrossRef]

19. Z. Yi, C. P. Liang, X. F. Chen, Z. G. Zhou, Y. J. Tang, X. Ye, Y. G. Yi, J. Q. Wang, and P. H. Wu, “Dual-band plasmonic perfect absorber based on graphene metamaterials for refractive index sensing application,” Micromachines 10(7), 443 (2019). [CrossRef]

20. R. Zia, J. A. Schuller, A. Chandran, and M. L. Brongersma, “Plasmonics: the next chip-scale technology,” Mater. Today 9(7-8), 20–27 (2006). [CrossRef]

21. Y. Fang and M. Sun, “Nanoplasmonic waveguides: towards applications in integrated nanophotonic circuits,” Light: Sci. Appl. 4(6), e294 (2015). [CrossRef]

22. S. Li, Y. Wang, R. Jiao, L. Wang, G. Duan, and L. Yu, “Fano resonances based on multimode and degenerate mode interference in plasmonic resonator system,” Opt. Express 25(4), 3525–3533 (2017). [CrossRef]

23. M. Wang, M. Zhang, Y. Wang, R. Zhao, and S. Yan, “Fano resonance in an asymmetric MIM waveguide structure and its application in a refractive index nanosensor,” Sensors 19(4), 791 (2019). [CrossRef]

24. Y. Deng, G. Cao, H. Yang, G. Li, X. Chen, and W. Lu, “Tunable and high-sensitivity sensing based on Fano resonance with coupled plasmonic cavities,” Sci. Rep. 7(1), 10639 (2017). [CrossRef]

25. D. V. Nesterenko, S. Hayashi, and Z. Sekkat, “Asymmetric surface plasmon resonances revisited as Fano resonances,” Phys. Rev. B 97(23), 235437 (2018). [CrossRef]

26. J. Chen, F. Gan, Y. Wang, and G. Li, “Plasmonic sensing and modulation based on Fano resonances,” Adv. Opt. Mater. 6(9), 1701152 (2018). [CrossRef]

27. C. Zhou, G. Liu, G. Ban, S. Li, Q. Huang, J. Xia, Y. Wang, and M. Zhan, “Tunable Fano resonator using multilayer graphene in the near-infrared region,” Appl. Phys. Lett. 112(10), 101904 (2018). [CrossRef]

28. A. Li and W. Bogaerts, “Tunable electromagnetically induced transparency in integrated silicon photonics circuit,” Opt. Express 25(25), 31688–31695 (2017). [CrossRef]

29. K. J. Boller, A. Imamoğlu, and S. E. Harris, “Observation of electromagnetically induced transparency,” Phys. Rev. Lett. 66(20), 2593–2596 (1991). [CrossRef]

30. G. Heinze, C. Hubrich, and T. Halfmann, “Stopped light and image storage by electromagnetically induced transparency up to the regime of one minute,” Phys. Rev. Lett. 111(3), 033601 (2013). [CrossRef]

31. Z. Chen, L. Yu, L. Wang, G. Duan, Y. Zhao, and J. Xiao, “Sharp asymmetric line shapes in a plasmonic waveguide system and its application in nanosensor,” J. Lightwave Technol. 33(15), 3250–3253 (2015). [CrossRef]

32. H. Lu, X. Liu, D. Mao, and G. Wang, “Plasmonic nanosensor based on Fano resonance in waveguide-coupled resonators,” Opt. Lett. 37(18), 3780–3782 (2012). [CrossRef]

33. Z. Chen, L. Yu, L. L. Wang, G. Y. Duan, Y. F. Zhao, and J. H. Xiao, “A refractive index nanosensor based on Fano resonance in the plasmonic waveguide system,” IEEE Photonics Technol. Lett. 27(16), 1695–1698 (2015). [CrossRef]

34. K. Wen, Y. Hu, L. Chen, J. Zhou, L. Lei, and Z. Meng, “Single/Dual Fano resonance based on plasmonic metal-dielectric-metal waveguide,” Plasmonics 11(1), 315–321 (2016). [CrossRef]

35. Y. C. Liu, B. B. Li, and Y. F. Xiao, “Electromagnetically induced transparency in optical microcavities,” Nanophotonics 6(5), 789–811 (2017). [CrossRef]

36. W. Suh, Z. Wang, and S. H. Fan, “Temporal coupled-mode theory and the presence of non-orthogonal modes in lossless multimode cavities,” IEEE J. Quantum Electron. 40(10), 1511–1518 (2004). [CrossRef]

37. Z. Tu, D. Gao, M. Zhang, and D. Zhang, “High-sensitivity complex refractive index sensing based on Fano resonance in the subwavelength grating waveguide micro-ring resonator,” Opt. Express 25(17), 20911–20922 (2017). [CrossRef]

38. Y. Huang, C. Min, P. Dastmalchi, and G. Veronis, “Slow-light enhanced subwavelength plasmonic waveguide refractive index sensors,” Opt. Express 23(11), 14922–14936 (2015). [CrossRef]

39. J. Feng, V. S. Siu, A. Roelke, V. Mehta, S. Y. Rhieu, G. T. Palmore, and D. Pacifici, “Nanoscale plasmonic interferometers for multispectral, high-throughput biochemical sensing,” Nano Lett. 12(2), 602–609 (2012). [CrossRef]

40. S. Raza, G. Toscano, A. P. Jauho, N. A. Mortensen, and M. Wubs, “Refractive-index sensing with ultrathin plasmonic nanotubes,” Plasmonics 8(2), 193–199 (2013). [CrossRef]

41. M. Ren, C. Pan, Q. Li, W. Cai, X. Zhang, Q. Wu, S. Fan, and J. Xu, “Isotropic spiral plasmonic metamaterial for sensing large refractive index change,” Opt. Lett. 38(16), 3133–3136 (2013). [CrossRef]

42. E. A. Velichko and A. I. Nosich, “Refractive-index sensitivities of hybrid surface-plasmon resonances for a core-shell circular silver nanotube sensor,” Opt. Lett. 38(23), 4978–4981 (2013). [CrossRef]

43. J. Chen, C. Sun, and Q. Gong, “Fano resonances in a single defect nanocavity coupled with a plasmonic waveguide,” Opt. Lett. 39(1), 52–55 (2014). [CrossRef]

44. T. S. Wu, Y. M. Liu, Z. Y. Yu, Y. W. Peng, C. G. Shu, and H. Ye, “The sensing characteristics of plasmonic waveguide with a ring resonator,” Opt. Express 22(7), 7669–7677 (2014). [CrossRef]

Ultra-compact high-sensitivity plasmonic sensor based on Fano resonance with symmetry breaking ring cavity

Abstract

1. Introduction

2. Plasmonic structure and theoretical model

3. Results and discussion

4. Conclusion

Funding

References

Cited By

Figures (6)

Equations (9)

Optics Express