VIS-NIR TMOKE enhanced dielectric-metal hybrid structure for high performance dual-channel sensing

Lixia Li; Lixia Li; Linqiao Du; Xueyang Zong; Yufang Liu

doi:10.1364/OE.502432

1. Introduction

The transverse magneto-optical Kerr effect (TMOKE) refers to the variation in the intensity of reflected light when the direction of an externally applied magnetic field changes, perpendicular to the plane of incident light [1–3]. This effect is highly dependent on the interaction between light and magnetic materials and exhibits high sensitivity to changes in the external environment. Therefore, it is commonly employed in sensing systems for detecting variations in the refractive index of the surrounding environment [4,5]. However, naturally occurring ferromagnetic materials such as iron, cobalt, and nickel exhibit weak TMOKE responses on smooth thin films. Typically, the magnitude of TMOKE for these metals is less than 0.1 or even smaller [6]. It is worth noting that this effect is somewhat dependent on the excitation conditions of surface plasmon resonance (SPR) [7,8]. When SPR is excited, this effect is also amplified accordingly. Therefore, the excitation of high-quality surface plasmon polariton (SPP) modes has been widely studied [9–12].

Currently the sandwich configuration as the standard sensing structure (prism excitation) have been extensively studied [8,13–15]. But, many defects of this configuration, such as large size, difficult integration and high cost, etc., further limit its development prospects. With the continuous development of subwavelength fabrication technology, various nanodevices have emerged, including one-dimensional periodic noble nanowire grating [9,16–20] and various two-dimensional periodic nanostructures such as noble metal-ferromagnetic metal-noble metal nanoholes [10,21] and nano disks [1], which have been extensively studied and reported. By satisfying the wave vector matching condition through diffraction coupling between periodic arrayed nanoelements, SPR is induced, thereby enhancing the TMOKE response of the structure. Although it overcomes the limitations of prism coupling mechanisms effectively, it also gives rise to new issues, namely the inevitable Ohmic losses within the metals, resulting in broad line widths in the TMOKE spectrum and ultimately leading to a lower quality factor of the system's sensing capabilities [22]. Considering this issue, researchers have attempted to achieve high-performance, low-loss sensing using periodic structures made of all-dielectric materials. But most reported magneto-optical all-dielectric gratings have primarily focused on enhancing the response (amplitude) of TMOKE [3,23], and the sensitivity of these sensors is not particularly very high [24,25]. More recently, the kind of dielectric-metal hybrid structures have been introduced as a compelling platform for sensing [26–28]. However, these sensing systems typically operate with only a single sensing channel, commonly referred to as single-channel sensing. This limitation also restricts the application of all-dielectric sensing structures. By contrast, dual-channel sensing can reduce the false alarm rate through multi-mode sensing, making it more adaptable to various lighting conditions and, importantly, enhancing its resistance to interference compared to single-channel sensing [29–32]. Reports on dual-channel sensing based on TMOKE, however, are rarely encountered in the literature.

In this paper, we propose a simple hybrid structure, which contains a one-dimensional bismuth iron garnet: yttrium iron garnet (BIG: YIG) nanowire arrays and thin film stack grown on an infinite thick silicon wafer. The Au film serves the purpose of exciting the propagating surface plasmon mode while effectively inhibiting the transmission of incident light. The results demonstrate that this design effectively avoids significant energy loss commonly observed in an all-metallic structure, resulting in ultra-narrow linewidths of 0.03 nm and 1.54 nm for the TMOKE response spectrum in the visible and infrared ranges, respectively. By adjusting the geometric parameters of the structure, dual-channel sensing in the visible light and infrared ranges can be achieved. During the variation of the refractive index of the external analyte in the range of 1.00∼1.05, the structure achieves a sensitivity of 285 nm RIU^-1 and the figure of merit (FOM) of 303 RIU^-1 in the infrared range. In the visible light range, the sensitivity reaches 553 nm RIU^-1, with a high FOM approaching 69125 RIU^-1. These results indicate that the system can be effectively applied in gas sensing applications. Furthermore, through numerical analysis of the SPP modes in the dielectric layer and the grating layer, the mechanism of enhanced magneto-optical effect through the interaction between light and magnetic materials is further elucidated. This work provides important insights for the study of enhanced magneto-optical effects and serves as a valuable reference for analysis of dielectric-metal grating sensors.

2. Theoretical and simulations

The mechanism of the sensor structure proposed is based on the transverse magneto-optical Kerr effect, which depicts actually the relative change of intensity in reflected light, and it originates from small variation of the off-diagonal component of the dielectric constant of magnetic medium in a magnetic field with different directions [33]. The magnitude of TMOKE is given by the following formula: [6,10]

(1)$$\textrm{ TMOKE } = \frac{{R( + H) - R( - H)}}{{R( + H) + R( - H)}}$$

where the R(+H) and R(−H) correspond to the reflectivity of the sample in the direction of positive and negative magnetic fields. For one-dimensional grating structure, the SPP modes can be excited by satisfying the wavevector matching condition. The wavevector of SPP under different magnetic field orientations can be described by the following analytical expression [24]:

(2)$${K_{sp}}({\pm} H) = {K_{sp}}(0) + m\frac{{i2d{{({{\varepsilon_d}{\varepsilon_m}{k_{inc}}} )}^2}}}{{({{\varepsilon_d} + {\varepsilon_m}} )({\varepsilon_d^2 - \varepsilon_m^2} )}}\left( { \pm \frac{{{\varepsilon_{xy}}}}{{{\varepsilon_{xx}}}}} \right)$$

with

(3)$${K_{sp}}(0) = {K_{inc}}\textrm{Sin} {\theta _{inc}} + m\frac{{2\pi }}{P}$$

where K_sp(0) and K_sp$({ \pm H} )$ are the SPP wavevector in the medium under demagnetized and magnetized, respectively; d is the thickness of the dielectric layer; ε_d and ε_m are the permittivity of dielectric and Au; ε_xy and ε_xx are the off-diagonal and diagonal components of the dielectric tensor in the BIG: YIG, respectively. K_inc and θ_inc represent the wavevector and incident angle, respectively, while m is an integer number indicating the diffraction order. Numerical simulations of the optical and MO responses are performed by using finite element package (COMSOL Multiphysics). In our calculations, the permittivity of Au is taken from the experimental data of Johnson and Christy (J&C) [34], and the optical properties of BIG:YIG are described anisotropic permittivity tensor of the following form [35]:

(4)$$\varepsilon = \left[ {\begin{array}{ccc} {{\varepsilon_{xx}}}&{{\varepsilon_{xy}}}&0\\ {{\varepsilon_{yx}}}&{{\varepsilon_{yy}}}&0\\ 0&0&{{\varepsilon_{zz}}} \end{array}} \right]$$

where

(5)$${\varepsilon _{xx}} = {\varepsilon _{yy}} = 5.53 - \frac{{v_p^2}}{{{v^2} + i{\gamma _0}v}}$$

(6)$${\varepsilon _{zz}} = \frac{{53.0{v^2} + 53.0i{\gamma _0}v - 13.25v_p^2}}{{13.84{v^2} + 13.84i{\gamma _0}v - 1.25v_p^2}}$$

(7)$${\varepsilon _{x\textrm{y}}} ={-} {\varepsilon _{yx}} = 0.012i$$

and ν_p = 0.477 PHz and γ₀ = 4.775 × 10⁻³ PHz.

Figure 1 depicts schematically the sensing structure and cross section studied, which contains a BIG: YIG nanowire arrays and multilayer film grown on an infinite thick silicon wafer. The thin film stack, from top to bottom, consists of the following layers: BIG, SiO₂, and Au. The optical thickness of Au film is fixed as 100 nm to act as a mirror to excite propagating surface plasmons at different interfaces and simultaneously prevent any light transmission.

Fig. 1. (a) Schematic drawing of the magneto-plasmonic sensor. (b) Cross-sectional diagram of the structure. The incidence plane is along the x-y plane, the magnetization (H) is oriented perpendicular to the incidence plane (along the z-axis). The device’s geometrical parameters include radius R, period P, BIG: YIG thickness h₁, SiO₂ film thickness h₂ and the Au film thickness is fixed at 100 nm. P-polarized light sources are incident obliquely on the surface of the structure at θ = 56$^\circ $. The incident medium is labeled analyte to make reference to gas sensing applications.

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Figure 2 illustrates the feasible fabrication process of the proposed structure. Initially, a 100 nm-thick layer of Au is deposited onto a silicon wafer using magnetron sputtering [36]. Subsequently, electron beam evaporation is employed to deposit layers of SiO₂ and BIG: YIG with thicknesses of 40 nm and 260 nm, respectively [37]. Finally, an ion beam etching process is utilized to etch a cylindrical grating array with a radius of 100 nm [38].

Fig. 2. The feasible fabrication process of the structure

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3. Results and discussion

3.1 Analysis for the proposed magneto-optics sensing system

In Fig. 3(a), we simulate the reflection spectrum of the structure under the background refractive index condition of air (n = 1), and the optimized structural parameters are R = 100 nm, P = 360 nm, h₁ = 60 nm, h₂ = 40 nm, and incidence angle θ = 56$^\circ $. It is obvious that two resonance modes appear at 665 nm and 811 nm. Due to the change in the direction of the external magnetic field, the rotation of the dielectric magnetization occurs, resulting in different magnitude shifts in the resonant wavelengths. To clearly observe the wavelength shift in the reflectance spectra under opposite magnetic field directions, the details at the resonance wavelengths are magnified in the inset. It can be seen that mode 2 exhibits a more pronounced shift compared to mode 1. The TMOKE response corresponding with Fig. 3(a) is plotted in Fig. 3(b), demonstrating a sharp Fano-like line shape. The full width at half maximum (FWHM) of the TMOKE curve with Fano-like line shape can be extracted accurately using the following analytical Fano interference model given as [21]:

(8)$$\delta (\lambda ) = A + B\frac{{{{\left( {\frac{{q\Gamma }}{2} + \lambda - {\lambda_0}} \right)}^2}}}{{{{\left( {\frac{\Gamma }{2}} \right)}^2} + {{({\lambda - {\lambda_0}} )}^2}}}$$

where A and B are constants representing the background and the overall peak height, respectively; q is the Breit–Wigner–Fano parameter determining the asymmetry of the resonance profile; Γ is the FWHM of the resonance; and λ₀ is the resonance wavelength. By Eq. (8), the FWHM are calculated to be 0.03 nm and 1.54 nm for the two modes, respectively. In consideration of the intuition of the two modes, it is necessary to give the electromagnetic field distribution at resonant wavelengths when explaining the different modes present in the structure. To better illustrate the resonance mode mechanism, under the same geometric parameters, Figs. 3(c)-3(f) give images of electromagnetic field distribution at resonant wavelengths of 665 nm and 811 nm, respectively.

Fig. 3. (a) Reflection spectra for the structure with different direction of magnetization. For clarity of the shift in the reflected light, the spectral range is zoomed in wavelength window in the inset. (b) Corresponding TMOKE spectrum calculated by Eq. (1). The FWHM of two modes is 0.03 nm and 1.54 nm respectively. (c) and (d) describe the normalized electric field distribution of the mode 1 and mode 2, respectively. (e) and (f) are the normalized magnetic field distribution at the corresponding mode 1 and mode 2.

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The normalized electromagnetic field distribution at wavelengths of 665 nm is shown in Figs. 3(c) and 2(e). It is clear that the electric field energy is mainly concentrated on the upper surface of the grating, while the magnetic field is mainly distributed inside the cylindrical grating. This finding aligns with the description provided in recent literature [39], thus leading us to identify it as the magnetic dipole resonance mode. The normalized electromagnetic field distribution at 811 nm is plotted in Figs. 3(d) and 3(f), clearly, the noticeable enhancement of magnetic field distribution on the surfaces of SiO₂ and Au films, which indicates the excitation of the SPP mode.

In Fig. 4, the optical and TMOKE responses of the structure have been extensively discussed for different incident angles and periods. As shown in Fig. 4(a), the reflectivity of the structure as a function of the angle of incidence, it can be seen that the resonance wavelength position of the two modes is redshifted with the increase of the incidence angle, which is due to the fact that the resonant wavelength has an approximately direct proportional relationship with the incidence angle in the case of a fixed grating constant. In this study, the focus of attention lies in the TMOKE response of the structure. As seen in Fig. 4(b), mode 1 exhibits significantly weaker TMOKE response compared to mode 2 at most angles. From the perspective of normalized electromagnetic field distributions, the electric and magnetic fields of mode 1 primarily concentrate in the upper layer of the structure, with limited interaction between the electromagnetic wave and the BIG film. By contrast, due to the interaction between the electromagnetic wave and the magnetic materials throughout the entire structure, mode 2 exhibits a relatively larger TMOKE response. For visual clarity, mode 1 is marked with red and blue dashed lines in Figs. 4(b) and 4(d), respectively. Considering the dual-channel sensing based on the TMOKE responses of the two modes, it is important to ensure that the TMOKE responses of both modes are not too weak and that the difference between them is not excessively large. Taking into account all factors, the final selected parameters are incident angle θ = 56° and P = 360 nm, which are represented by black dashed lines in Figs. 4(b) and 4(d). All subsequent optimizations of the structural parameters will be based on these values.

Fig. 4. Influence of incident angle and period on optical responses for the sensing system. (a) Reflection spectra as a function of incident angle. (b) TMOKE responses for structures corresponding with (a). (c) Reflection spectra as a function of period. (d) TMOKE responses for structures corresponding with (c).

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3.2 Parameter optimization and analysis

In this section, the influence of geometric parameters on different modes and the potential mechanisms of different modes are thoroughly discussed. Figure 5 depicts the optical response and TMOKE response of devices with different geometric parameters. Figures 5(a)-5(c) illustrate the variation of the structure's reflectance as a function of wavelength for different parameters: (a) nanowire radius R, (b) BIG: YIG thickness h₁, and (c) SiO₂ thickness h₂. Figure 5(a) displays the reflection spectra of the structure for nanowire radius ranging from 50 to 100 nm with a step size of 10 nm. It can be seen mode 1 from non-existent to gradual appearance, which is because, under a fixed grating constant, small-sized cylindrical gratings have relatively larger spacing and are unable to excite the dipole resonance mode. The fact that the magnetic field in Fig. 6(b) is solely distributed on the surface of the Au film rather than inside the nanowires provides compelling evidence for the judgment. As the grating radius increases, the resonance occurs when the size of nanowires satisfies the condition λ₀/n ≈ 2R [40], where R is the radius of the nanowire, n is the refractive index of BIG: YIG and λ₀ is the free space wavelength. And the diffraction between adjacent gratings enhances, making the dipole resonance mode possible. Meanwhile, the FWHM of mode 1 narrows as the resonance intensity increases. During this process, mode 2 shows little variation, which is attributed to the fact that the resonance position of the SPP mode depends only on the refractive indices (permittivity) of the materials on both sides of the interface. Particularly, at R = 180 nm, the reflectance spectra of the structure exhibit a significant decrease in resonance intensity for both modes. This is because when R = P/2, the cylindrical gratings are densely packed, and their surface resembles a smooth film. The collective diffraction effects of the grating are weakened, resulting in a decrease in the resonance intensity of both modes.

Fig. 5. Effects of geometric parameters on optical and MO responses. Reflection of the structure in the absence of an external magnetic field as a function of (a) nanowire radius R (h₁ = 60 nm and h₂ = 40 nm), (b) thickness of BIG: YIG h₁ (R = 100 nm and h₂ = 40 nm), (c) thickness of SiO₂ h₂ (R = 100 nm and h1 = 60 nm), respectively. (d)–(f) The corresponding TMOKE spectra under opposite magnetic field conditions.

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Fig. 6. The optics response and normalized magnetic field under different structural parameters: (a) R = 180 nm & (b) R = 50 nm (h₁ = 60 nm, h₂ = 40 nm). (c) h₁ = 100 nm & (d) h₁= 0 nm (R = 100 nm, h₂ = 40 nm). (e) h₂ = 100 nm & (f) h₂ = 0 nm (R = 100 nm, h₁ = 60 nm), respectively.

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It should be noted that the influence mechanism of h₁ and h₂ on the modes is similar, which can be preliminarily observed from Figs. 5(c)-5(f). This is because the normalized magnetic field distribution of h₁ and h₂ in Fig. 5 is very similar. In Fig. 4(b), when h₁ is small (less than 50 nm), mode 1 is not prominent, and as h₁ increases, it gradually appears with little change in resonance position. Mode 2 undergoes a slight redshift. From the previous analysis on R, the resonance position of mode 1 has an almost linear relationship with R. Therefore, under fixed R conditions, mode 1 does not shift. Mode 2 has been identified as the SPP mode, and its resonance position is determined by the dielectric constants of the materials on both sides of the interface. Theoretically, once the materials are determined, the position of the resonance wavelength is also determined. However, a redshift phenomenon occurs when changing the thickness of h₁ or h₂. This is because the Au film used in our structure acts as a reflective mirror, leading to the excitation of both the magnetic dipole resonance and its mirror image on the nanowires [41]. During the mutual interaction between these two symmetric magnetic dipoles with respect to the Au film, a resonance similar to a Fabry-Perot cavity is formed. As a result, when change the thickness of h₁ or h₂, the Fabry-Perot cavity's cavity length is simultaneously altered in this scenario, thereby affecting the magnetic dipole resonance. This is also why mode 1 in Figs. 5(b) and 5(c), although its resonance position remains almost unchanged, exhibits an overall trend of redshift. In the process of the minute redshift of mode 1, it gradually approaches mode 2, causing coupling between the two modes and resulting in the redshift of mode 2. This reasoning process is verified by the magnetic field distributions in Fig. 6(a) for R = 180 nm. Mode 1 has the characteristics of SPP magnetic field distribution and mode 2 has the characteristics of magnetic dipole resonance. This is the result of the coupling of mode 1 and mode 2. The optical corresponding analysis process of the structure in h₂ is basically the same as that in h₁.

Figures 5(d)-5(f) show the evolution of the TMOKE spectra for different structural parameters. The TMOKE signal represents the relative change in reflectance and exhibits sharp peaks resembling a Fano-like line shape. The nanostructure exhibits a large TMOKE amplitude close to the theoretical limit under specific parameter [24], far surpassing the prism-based coupling mechanisms. Considering the requirements for sensing applications of both modes, it is essential to avoid a significant difference in the TMOKE amplitudes between the two modes. Therefore, the final and optimized design parameters are fixed as h₁ = 60 nm and h₂= 40 nm. These parameters ensure a balanced and suitable TMOKE response for both the magnetic dipole resonance mode and the SPP mode, making the structure ideal for our intended dual-channel refractive index sensing application. In previous reports, the amplitude of TMOKE was only in the range of 0.01-0.1 or even smaller [4,10]. Undoubtedly, our work provides valuable insights for improving the magneto-optical response of systems and holds promising applications in other fields.

4. Refractive index sensitivity

The magneto-optics platform in the ultra-resolution sensing application is the main issue in this work. In this section, the TMOKE response of the system is studied by varying the refractive index (n) of the incident medium and the refractive index of the adjacent grating gaps to ensure the quality of sensing performance. Based on the normalized electric field distribution shown in Fig. 3, it can be inferred that mode 1 exhibits higher sensitivity compared to mode 2. This is because the sensitivity of the modes is closely related to their field distribution characteristics. Generally, modes with larger field distributions are more sensitive to variations in their surroundings, whereas modes with smaller field distributions are less sensitive to such changes. Observing the field distributions of mode 1 and mode 2, the field distribution of mode 2 is localized solely within the SiO₂ thin layer, it is evident that mode 1 has a significantly larger field distribution than mode 2. Furthermore, based on the FWHM of the two modes, it can be inferred that mode 1 has a higher FOM compared to mode 2. After calculation, both modes demonstrate excellent refractive index (RI) sensing capabilities. RI sensitivity is defined as the ratio of the offset of the resonance wavelength to the RI change of the medium $S = \frac{{\Delta \lambda }}{{\Delta n}}$, and FoM, defined as the ratio of the sensitivity to the spectral FWHM: $FOM = \frac{S}{{FWHM}}$. Based on the measurement principle of Kerr effect, Fig. 7(a) illustrates the optical responses of the nanoscale structure in a gas environment, showcasing the redshift of both modes as the refractive index (RI) varies from 1 to 1.05 in increments of 0.005. Figure 7(b) plots the TMOKE responses corresponding Figs. 7(a), 7(c) and 7(d) illustrate the peak positions in the spectra as a function of RI. The results of linear fitting exhibit high RI sensitivities, with mode 1 at 553 nm RIU^-1 and mode 2 at 303 nm RIU^-1. This also confirms our previous speculation. By utilizing Eq. (8), the linewidth of the TMOKE curve can be accurately extracted, resulting in a FOM range of 2513∼69125 RIU^-1 for mode 1 and 185∼303 RIU^-1 for mode 2.

Fig. 7. (a) Optics response of structure as a function varies with refractive index. (b) TMOKE response corresponding to (a). (c) sensitivity and FOM of mode1. (d) sensitivity and FOM of mode 2.

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Table 1 presents the specific parameters of the proposed sensor under different refractive indices, including resonance wavelength shifts, FWHM, and FOM. Table 2 provides a comparison of the performance parameters of the sensor based on TMOKE in a single channel with those reported in previous studies. The detection limit, often referred to as LOD (Limit of Detection), is another performance metric for evaluating the sensor's capabilities. It is defined as

(9)$$\textrm{DL} = \frac{{R(RIU)}}{S}$$

where S represents sensitivity, and R(RIU) denotes the resolution of the sensor, which is defined as follows [43]:

(10)$$R(RIU) = \frac{{\Delta n \times \Delta {\lambda _{\min }}}}{{\Delta {\lambda _{peak}}}}$$

where $\Delta {\lambda _{\min }}$ and $\Delta {\lambda _{peak}}$ represent the variations in the resonance peak and resonance valley positions, respectively, in the TMOKE spectral curve.

Table 1. Resonant shift for each gas RI and performance

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Table 2. Comparison of performance parameters with previously reported works

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5. Conclusion

In summary, we propose a hybrid structure consisted of one-dimensional BIG: YIG nanowire arrays and thin film stack, which grown on an infinite thick silicon wafer. By replacing ferromagnetic metals with magnetic dielectric materials, the high losses present in an all-metal sensing system have been cleverly avoided. By exiting magnetic dipole resonance mode within the cylindrical grating and the SPP mode on the interface between dielectric and Au film, dual-channel sensing in the visible and infrared regions are achieved while enhancing the TMOKE intensity. The sensitivity in the visible light range reaches 553 nm RIU^-1, while in the infrared range it reaches 285 nm RIU^-1. The FOM of the nanostructure sensor (reaching up to 69125 RIU^-1 in the visible range and 303 RIU^-1 in the infrared range) are significantly improved. This research demonstrates enormous potential in the fields of high-resolution and dual-channel sensing. It provides a theoretical basis for future multi-channel sensing based on the transverse magneto-optical Kerr effect (TMOKE) and mode analysis of the grating.

Funding

National Natural Science Foundation of China (62105095, U1804261); Natural Science Foundation of Henan Province (202300410238); National Scientific Research Project Cultivation Fund of Henan Normal University (20210381, 2021PL22).

Disclosures

The authors declare no conflicts of interest.

Data availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

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Refractive index	mode 1 resonance position (nm)	FWHM (nm)	FOM 1 (RIU^-1)	mode 2 resonance position (nm)	FWHM (nm)	FOM 2 (RIU^-1)
1.000	665.0	0.03	18433	812.0	1.54	185
1.005	667.5	0.03	18433	813.5	1.52	188
1.010	670.2	0.09	6144	814.9	1.47	194
1.015	672.8	0.07	7900	816.4	1.43	199
1.020	675.5	0.06	9217	817.8	1.37	208
1.025	678.3	0.04	13825	819.2	1.32	216
1.030	681.1	0.06	9216	820.6	1.26	226
1.035	683.9	0.008	69125	822.0	1.2	238
1.040	686.7	0.07	7900	823.4	1.15	248
1.045	689.6	0.12	4608	824.9	1.06	269
1.050	692.4	0.22	2513	826.3	0.94	303

Ref		Modulation method	Work range(nm)	S(nm/RIU)	FOM (max)	DL (RIU²/nm)
[1]		Wavelength	700∼1100	717	7000	N/A
[4]		Angle	57∼64	190	3000	N/A
[10]		Wavelength	690∼730	659	2500	N/A
[21]		Wavelength	730∼750	722	25000	N/A
[6]		Wavelength	650∼750	659	4200	N/A
[42]		Angle	40∼50	159	1250	N/A
This work	mode 1	Wavelength	660∼700	553	69125	0.0052
This work	mode 2	Wavelength	810∼830	285	303	0.0050

Refractive index	mode 1 resonance position (nm)	FWHM (nm)	FOM 1 (RIU^-1)	mode 2 resonance position (nm)	FWHM (nm)	FOM 2 (RIU^-1)
1.000	665.0	0.03	18433	812.0	1.54	185
1.005	667.5	0.03	18433	813.5	1.52	188
1.010	670.2	0.09	6144	814.9	1.47	194
1.015	672.8	0.07	7900	816.4	1.43	199
1.020	675.5	0.06	9217	817.8	1.37	208
1.025	678.3	0.04	13825	819.2	1.32	216
1.030	681.1	0.06	9216	820.6	1.26	226
1.035	683.9	0.008	69125	822.0	1.2	238
1.040	686.7	0.07	7900	823.4	1.15	248
1.045	689.6	0.12	4608	824.9	1.06	269
1.050	692.4	0.22	2513	826.3	0.94	303

Ref		Modulation method	Work range(nm)	S(nm/RIU)	FOM (max)	DL (RIU²/nm)
[1]		Wavelength	700∼1100	717	7000	N/A
[4]		Angle	57∼64	190	3000	N/A
[10]		Wavelength	690∼730	659	2500	N/A
[21]		Wavelength	730∼750	722	25000	N/A
[6]		Wavelength	650∼750	659	4200	N/A
[42]		Angle	40∼50	159	1250	N/A
This work	mode 1	Wavelength	660∼700	553	69125	0.0052
This work	mode 2	Wavelength	810∼830	285	303	0.0050

VIS-NIR TMOKE enhanced dielectric-metal hybrid structure for high performance dual-channel sensing

Abstract

1. Introduction

2. Theoretical and simulations

3. Results and discussion

3.1 Analysis for the proposed magneto-optics sensing system

3.2 Parameter optimization and analysis

4. Refractive index sensitivity

5. Conclusion

Funding

Disclosures

Data availability

References

Data availability

Cited By

Figures (7)

Tables (2)

Equations (10)

Optics Express