Tunable Fano Resonance in E-Shape Plasmonic Nanocavities - The

Article pubs.acs.org/JPCC

Tunable Fano Resonance in E‑Shape Plasmonic Nanocavities Bo Sun,*,†,‡ Lixia Zhao,*,† Chao Wang,*,§ Xiaoyan Yi,† Zhiqiang Liu,† Guohong Wang,† and Jinmin Li† †

Semiconductor Lighting Technology Research and Development Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China ‡ Department of Physics, Tsinghua University, Beijing 100084, China § School of Energy Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China S Supporting Information *

ABSTRACT: The optical properties of e-shape plasmonic nanocavities have been studied. Due to the destructive interference of the quadrupole resonance of the c-shape nanoring with the overlapping dipolar resonance of the nanorod, a tunable Fano resonance within a wide range of spectra from visible light to mid-infrared (mid-IR) spectrum have been observed. The spectral positions and modulation depths of the Fano resonances can be tuned with different geometry parameters of nanocavities, and the performance (modulation depth of spectra and near-field enhancement) of e-shape plasmonic nanocavities can be further improved by optimization of the nanocavity’ radiation characteristics using a dielectric layer (SiO2). Furthermore, capacitive coupling between c-shape nanoring and nanorod antenna was found to be asymmetric, in which Fano resonance can be modulated to symmetric/antisymmetric quadrupole−dipole by moving the nanorod in the positive/negative direction of the x axis. This work opens up new opportunities for engineering spectral features and optimizing performance of a broad range of plasmonics devices. enhancement of induced field, Fano resonances have already been used for various applications, such as plasmonic rulers,6 chemical or biological sensors,23 switching, and electrooptics.24−26 To further develop those applications based on Fano resonance, it is highly desired to improve the light confinement of near-field and broad spectral region. Very recently, it was reported that the resonance position and amplitude of light confinement were mainly controlled by the coupling with subradiant modes, which is directly determined by the geometrical configuration of the nanostructures.27 But how to achieve subradiant plasmon modes (quadrupole resonance, octupole resonance, etc.) in plasmonic nanostructures is still an open question. One difficulty is that the subradiant plasmon modes cannot directly couple with the electric field of the incident light when the size of the nanostructure is much smaller than the wavelength of the excitation light. Subradiant plasmon modes can be formed at large size of the nanostructure due to the phase retardation effect.28 However, the excitation of those subradiant plasmon modes usually require electric field with grazing incident, which hamper these applications as most of these applications rely on the excitation of resonances by light at normal incidence. Subradiant plasmon modes in previous reported nanostructure,

1. INTRODUCTION Localized surface plasmon resonances (LSPRs)1 in metallic nanostructures have attracted considerable attention in the past decades due to the ability to manipulate light at a deep subwavelength scale and thereby causing extremely strong local fields near the metal surfaces. Typically, the line-width of plasmon resonance in such metallic nanostructures described by the Lorentz line shape would be large due to the large radiation damping2 of the plasmon mode, which severely hampers its applications. Recently, Fano resonances3−6 which arise from the interference between superradiant and subradiant modes have been paid tremendous attention due to the narrow and asymmetric line shapes. These asymmetric line-shapes have been observed in various plasmonic systems which involve some form of interaction between superradiant and subradiant modes. For example, plasmonic oligomers consisited of three,5 four nanoparticles,7 and even larger aggregates8−10 can exhibit sharp Fano interference due to the linear combinations of the plasmon modes in each constituented nanoparticle with sufficiently small separations of interparticle. Both dolmentype11−15 slab structures and the nonconcentric ring/disk cavity16,17 have shown Fano resonances in the optical regime. In addition, Fano resonances have also been observed in some systems with the interaction between a continuum interband and a dipolar LSPR18,19 or various arrays or grating structures20−22 with narrow diffractive resonances and broad plasmon modes. Because of the narrow spectral width and large © 2014 American Chemical Society

Received: October 18, 2013 Revised: September 23, 2014 Published: September 29, 2014 25124

dx.doi.org/10.1021/jp4105882 | J. Phys. Chem. C 2014, 118, 25124−25131

The Journal of Physical Chemistry C

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Figure 1. (a) Schematic diagram of an e-shape plasmonic nanocavity. The geometry parameters are the following: outer (R2) and inner radius (R1) of the c-shape ring, the length, L, and the width, W, of the nanorod, the central offset, s, and the thickness, H, of the nanocavity. The ŝ and â axis represent the symmetric and antisymmetric axis of the c-shape nanoring, respectively. (b) Extinction spectra of the c-shape nanoring in the presence of incident light polarization along â (gray curve), ŝ (blue curve), and x (magenta curve) axis, where the geometry parameters of the c-shape nanoring are R1 = 80 nm, R2 = 100 nm, and H = 40 nm. (c−f) Field enhancement of the antisymmetric dipole (I), symmetric dipole (II), antisymmetric quadrupole (III), and symmetric quadrupole (IV) modes, respectively. (g−j) The corresponding charge density distributions of the antisymmetric, symmetric dipole, and quadrupole modes, respectively.

such as dolmen plasmonic nanostructure,11−15 Ring/Disk system28−32 should first excite a bright dipole resonance as the excitation source. Till now, it was also a challenging task to design plasmonic structures exhibiting Fano resonances at specific wavelengths with a tunable local light confinement for their complex nature. In addition, capacitive coupling between superradiant and subradiant modes is generally symmetric, and asymmetric capacitive coupling has rarely been reported. In this study, we designed an e-shape nanocavity plasmonics nanostructure with c-shape nanoring and nanorod, which exhibits a tunable Fano resonance within the broad range from visible to infrared spectrum. It has demonstrated excellent optical properties with the combination effects of both c-shape nanorings and nanorods. The nanorods serve as a superradiant dipole antenna which can strongly couple to the incident field and show an excellent optical tunability, large-field enhancements, and less sensitive to fabrication tolerances.33 The cshape nanoring can directly provide nonradiative subradiant modes in normal incidence without the excitation of dipole resonance as the excitation source.34 It has also been shown that the modulation depth and spectral position of Fano resonance can be modulated by accurate tuning of the geometry parameters of the nanocavity. Furthermore, the performance (modulation depth of spectra and near field enhancement) of the e-shape nanocavity can be further improved by the radiation engineering with a dielectric spacer coated on metal ground planes. In addition, we found that

capacitive coupling between the c-shape nanoring and the nanorod antenna was asymmetric.

2. RESULTS AND DISCUSSION The e-shape gold plasmonic nanocavity studied in this paper was put on a glass substrate as the schematic diagram shows in Figure 1a. The c-shape nanoring had splits of arc length 120 deg. The parameters used to characterize the geometry include: the inner and outer radius R1, R2 of c-shape nanoring, the length, L, and width, W, of the nanorod, the thickness, H, and the center offset, s. The extinction spectra of nanostructure were performed using the finite-difference time domain (FDTD) method with the implement of the Lumerical software package 7.5 (Lumerical Solutions, Inc.). A total-field/scatteredfield source was used as an incident field into the simulation region. The background refractive index of 1 was treated as uniform. The simulation area was discretized by a threedimensional grid mesh, where the grid step is 3 nm in x-, y-, and z-directions. Figure 1b shows the extinction spectra of the c-shape nanoring with the incident light normal to the nanostructure plane. Two unit vectors were defined to describe the geometry of the c-shape nanoring: ŝ along the symmetry axis of the cshape nanoring and â perpendicular to ŝ. For a given polarization light, it was convenient to resolve the incident ⇀

electric field Ei along ŝ and â direction: Ei = Eaiea⃗ i + Esies⃗ i, where 25125



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ea⃗ i and es⃗ i are basis vectors. As indicated in Figure 1a, the components of the electric field along the ŝ and â directions can be represented by Esi = Ei cos[(5π)/6−θ] and Eai = Ei cos[θ− (π/3)], respectively, where θ is the polarization angle of incident light. It has been known that both the “symmetric” and “antisymmetric” modes are excited in split nanoring due to the symmetry breaking, but the “symmetric” modes are excited by light parallel to the symmetric axis of the nanostructures, while for the “antisymmetric” modes, they are excited by light perpendicular to the symmetric axis of the nanostructures.35 The gray line in Figure 1b is the extinction spectrum of the cshape nanoring with incident polarization light along the â direction (θ = π/3). Two resonances at ∼1772 and 759 nm can be observed. According to the electric field and charge density distributions shown in Figure 1 (panels c, e, g, and i), they are antisymmetric dipole (I) and quadrupole (III) resonance, respectively. The blue line shows the extinction spectrum of the c-shape nanoring with incident polarization light along the ŝ direction [θ = (5π)/6]. In this case, there are also two resonance peaks at ∼997 and 667 nm, which corresponding to symmetric dipole (II) and quadrupole (IV) resonance of cshape nanoring from the electric field and charge density distributions in Figure 1 (panels d, f, h, and j). However, if the polarization is along the x axis (θ = 0), all these four resonances of the c-shape nanoring can be excited, as indicated by the magenta line. This may be because that for the x direction, polarization light can have the components of the incident electric field in both ŝ and â direction of the c-shape nanoring, which can excite the “symmetric” and “antisymmetric” modes at the same time. The quality factor (Q) (defined as the resonant wavelength over the width of the resonance) of antisymmetric, symmetric dipole, and quadrupole modes are 9.64, 8.29, and 25.3 and 27.2, respectively. The Q factor of the subradiant quadrupole modes is 3 times larger than the superradiant dipole modes. Those resonances excited in the c-shape nanoring are different from the normally reported nanoring structures (Figure S1 of the Supporting Information), in which only dipole resonance can be excited with normal incident, while the antisymmetric dipole and quadrupole resonances will be activated for grazing incidence because of the phase retardation effect.28 The excellent subradiant resonances found in the cshape nanoring can make them good candidates to interact with other superradiant antenna, where the local light confinement and line shape of Fano resonance can be easily modified. Figure 2a shows the extinction spectra of the e-shape nanocavity in the absence of central offset (s = 0 nm). An apparent dip at the resonance wavelength of 776.3 nm was observed, where the dipole resonance of nanorod and the quadrupole resonance of the c-shape nanoring are spectrally overlapped. As shown in Figure 2 (panels b, c, and d) compared with the isolated nanorod antenna and c-shape nanoring, the field intensity of the coupled nanorod antenna in the e-shape nanocavity has been reduced, but the field intensity of the coupled c-shape nanoring has been dramatically enhanced. This phenomenon can be associated with the destructive interference of the quadrupole resonance with a broadened dipole resonance. The formation of antisymmetric quadrupole−dipole Fano resonances can also be verified by the charge density distribution shown in Figure 3e, which shows that the strong coupling between the quadrupole mode of the c-shape nanoring and dipole mode of nanorod can produce asymmetric line shape with sharp spectral features and lead to a strong near-field enhancement.

Figure 2. (a) Extinction spectra of the nanorod (gray solid), c-shape nanoring (blue solid), and e-shape nanocavity (red solid), where the geometry parameters are R1 = 80 nm, R2 = 100 nm, W = 40 nm, H = 40 nm, L = 120 nm, and s = 0 nm. Electric field distribution of (b) nanorod, (c) c-shape nanoring, and (d) e-shape nanocavity at the Fano resonance dip (776.3 nm). Inset of (b) shows the charge density distribution of the noncoupled nanorod antenna. (e) Charge density distribution of e-shape nanocavity at the Fano resonance dip.

In the following, we are going to show that the Fano resonance can also be modified by changing geometry parameters of the c-shape nanoring and nanorod, such as (1) the length of the nanorod, (2) the radii of the c-shape nanoring, and the (3) central offset s. Figure 3a shows the spectra characteristics of the e-shape nanocavity with different lengths of nanorod, the dip of the Fano resonance moved from 776.3 to 795.1 nm with the length increasing from 120 to 140 nm, but no dip can be formed in the extinction spectra for the nanorod with length 110 nm. The corresponding dipole resonance of the nanorod and quadrupole resonance of the c-shape nanoring are shown in Figure 3b, respectively. It can be seen that the spectra of the nanorod (110 nm) and c-shape nanoring are overlapped. The large gap between nanorod and nanoring may hinder the generation of the Fano resonance, which indicates that the near-field interaction between the superradiant and subradiant modes is an important factor to generate Fano resonances. Figure 4 shows the spectra characteristics of e-shape nanocavity by changing the radius of the c-shape nanoring. The length, L, of nanorod was controlled (with the relation of L = 2R1 − 20, where R1 is the inner radius of the c-shape nanoring). With the inner radius of the c-shape nanoring increasing from 50 to 140 nm, the peak position of antisymmetric quadrupole resonance move from 640.2 to 1130.5 nm. Figure 4 (panels a−f) shows the extinction spectra of the nanorod, where the peak position of dipole resonances shift from 656.3 to 1153.6 nm with the length increasing from 80 to 220 nm. The corresponding extinction spectra of the eshape nanocavity exhibits Fano-resonance, where the dip of the Fano resonance increases from 642.2 to 1074.8 nm. This wide spectra modulation from visible light to mid-infrared is very important for sensing applications. Next, we will show that the line shape of Fano resonance can also be influenced by the near-field interaction between the superradiant and subradiant modes. Generally, symmetry breaking configuration30,31was used to control the line shape of Fano resonance. Here, the spectra characteristics of e-shape nanocavity was investigated by introducing central offset. The central offset, s, has been defined negative (positive) as the nanorod antenna moves to the negative (positive) direction of the x axis. The transmittance and absorbance spectra dependence on s (in the negative direction) are presented in Figure 5 (panels a and b). With the absolute value of the central 25126



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Figure 3. (a) Extinction spectra of e-shape nanocavity as a function of the nanorod length, L, where structure parameters are R1 = 80 nm, R2 = 100 nm, W = 40 nm, H = 40 nm, and s = 0 nm. (b) Extinction spectra of c-shape nanoring and nanorod antenna for different lengths, where the gray dash line represents the antisymmetric quadrupole resonance of the c-shape nanoring.

Figure 4. (a−f) Extinction spectra of the nanorod antenna as a function of L (from 260 to 80 nm but W fixed at 40 nm); (g−l) extinction spectra of the c-shape nanoring as a function of the radius R1 (from 140 to 50 nm but width of nanoring fixed at 20 nm); (m−r) the corresponding extinction spectra of e-shape nanocavity. The orange dash arrows in the middle and right panels show the antisymmetric quadrupole resonance of the c-shape nanoring and Fano resonance of e-shape nanocavity, respectively.

offset s increasing, the transmittance of the nanocavity was dramatically enhanced but suppressed for the absorbance. This phenomenon is called plasmonic EIT,4,14 where a destructive interference occurs between the coupling of the superradiant nanorod antenna with the incident light and the subradiant quadrupole nanoring with the dipole antenna. To further explore the EIT spectral characteristics, the electric field distributions of the e-shape nanocavity at the absorbance dip for different s were calculated and shown in Figure 5 (panels c−f). With the absolute value of s increasing, the electric field intensity for the nanorod antenna decreases but increases for the c-shape nanoring. This means that the coupling strength between dipole mode of nanorod and quadrupole mode of c-shape nanoring has been dramatically enhanced with increasing the absolute value of s. This local-field enhancement in the c-shape nanoring indicates that the

radiative damping of the e-shape nanocavity can be effectively suppressed, and the EIT-like spectra is only limited by the nonradiative damping (the intrinsic Drude loss of the metal). Figure 6a shows the extinction spectra of e-shape nanocavity as a function of central offset s in the positive direction. Compared with the negative value of s shown in Figure 5, a new Fano-like dip (λ = 677.8 nm) appeared in the extinction spectra for the positive value of s. Furthermore, it can be see that the modulation depth of this Fano dip (λ = 677.8 nm) gradually increased with the central offset s increasing. In accordance with the electric field intensity and charge density distribution of this dip shown in Figure 6 (panels b and c), it can be inferred that the new Fano dip originated from the destructive interference between the dipole resonance of the nanorod and the symmetric quadrupole resonance of the c-shape nanoring. 25127



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Figure 5. (a) Transmittance and (b) absorbance spectra of e-shape nanocavity with central offset s varying from −15 to 0 nm, where the olive dash dot line represents the position of the antisymmetric quadrupole−dipole Fano resonance. (c−f) Corresponding field enhancement distribution of the e-shape nanocavity at Fano dip.

nanocavity. As indicated in Figures 5 and 6, it can be seen that capacitive coupling between the c-shape nanoring and the nanorod antenna was asymmetric. The symmetric quadrupole− dipole Fano resonance is activated when the nanorod antenna moves in the positive direction of the x axis, but antisymmetric quadrupole−dipole Fano resonance will happen when it moves in the negative direction. To achieve deeper understanding of this phenomena, we analyze the processes of capacitive coupling between these two antennas. As shown in Figure S2 of the Supporting Information, it can be seen that capacitive coupling between the left side of the nanorod and the B and C parts of the c-shape nanoring is predominant for the negative s. However, when the nanorod antenna moves in the positive direction of the x axis, the near-field interaction between the right side of the nanorod and the A part of the c-shape nanoring dominates the process of capacitive coupling. Moreover, the phase of the coupled nanorod antenna has changed with π, compared with the noncoupled nanorod antenna. This may be due to the charge redistribution in the nanorod antenna and the c-shape nanoring due to the intensive right-side capacitive coupling. More intuitive understanding of this phenomenon should represent the nanorod and c-shape nanoring as circuit nanoelements,39 which will be the focus of future work. To further understand the mechanism of this coupling process, the electromagnetic theory27,40 based on Maxwell’s equation have been used to explore the plasmonic Fano resonances. The spectrum with the Fano-like asymmetric line shape caused by the interference between the direct excitation of the continuum and the excitation of the dark mode through its coupling to the continuum can be regarded as

Figure 6. (a) Extinction spectra of e-shape nanocavity as a function of central offset s (varying from 0 to 20 nm), where the gray and violet dash lines represent the position of antisymmetric and symmetric quadrupole−dipole Fano resonance. (b−c) Field enhancement and charge distribution of symmetric quadrupole−dipole Fano resonance at the dip.

In the previous study, capacitive coupling plays an important role in the formation of Fano resonance.36 Furthermore, it was found that capacitive coupling between superradiant and subradiant modes in the symmetric nanostructure, such as ring/disk plasmonic nanocavities,37,38 or in the asymmetric nanostructure, such as gold nanoshells with an off-centered core32 and symmetry breaking ring/disk system,16 are symmetric. That is completely different from our e-shape 25128



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Figure 7. Resonance line shape of e-shape nanocavity influenced by electromagnetic interactions. (a−c) Reflection spectra of e-shape nanocavity for various s, where red solid line and black dash represent numerical simulated and fitted results with σt (eq 3), respectively. (d−f) Asymmetric line shapes σa extracted from the fitting (eq 1), where the violet rectangle show the resonance width, Wa. (g−h) Extracted asymmetric parameter q and modulation damping parameter b for various s.

( σ = a

2

ω2 − ωa 2 2Waωa

(

)

+q

ω2 − ωa 2 2Waωa

coupling strength in our system, the parameters Wa, q, and b for different s were compared as well. Figure 7 (panels d−f) shows the asymmetric line shape produced by using the fitting parameters according to eq 1. It was found that the width of asymmetric line shape increased with the absolute value of s increasing, which indicates that mode coupling becomes stronger between the superradiant and subradiant modes. This is also consistent with the previous simulation results. The fitting parameters b and q were also shown in Figure 7 (panels g and h). The parameter b decreased, while the absolute value of the parameter q increased with the absolute value of s increasing. This result demonstrated that intrinsic losses of eshape nanocavity decreased with the absolute value of s increasing, which is in good agreement with the simulation results (Figure 5). The amount of field enhancement in the local region of the nanostructure is the most important parameter to characterize its performances. The maximum field enhancement in the nanostructure can be achieved through optimization of the nanostructures’ radiation characteristics.41 In coupled mode theory,42 the field enhancement of the nanostructure at the resonance can be represented as |Eloc|2 ∝ Q/(Qrad)Q/(Veff)|Ei|2, where Eloc and Ei are the local field amplitude of nanostructure and the field amplitude of incoming excitation light, respectively and Veff is the effective mode volume of the nanostructure. The total quality factor (Q) is the summation of the radiation quality factor (Qrad) and the absorption quality factor(Qabs): Q−1 = Qrad−1 + Qabs−1. Compared with the effective mode volume (Veff) and Qabs, the optimization of radiation quality factor (Qrad) is more effective in field enhancement of the nanostructure. Therefore, in order to further improve the e-shape nanocavity performance, we placed

+b

2

)

+1

(1)

Where ωa is the resonance central spectral position, Wa gives an approximation of its spectral width, q is the asymmetry parameter, and b is the modulation damping parameter originating from intrinsic losses. Meanwhile, the bright dipole resonance strength follows a symmetric pseudo-Lorentzian line shape as a function of the frequency ω: σs =

a2

(

ω2 − ωs 2 2Wsωs

2

)

+1

(2)

Where ωs and Ws are the spectral position and width, respectively. The entire system resonance regarded as the Fanolike asymmetric line shape at the background of symmetric pseudo-Lorentzian line shape can be obtained as follows: σt(ω) = σs(ω)σa(ω)

(3)

In electromagnetic theory, the width of the asymmetric resonance is mainly determined by the modes coupling, while intrinsic losses drastically affect the modulation depth and the symmetry of the resonance. The frequency position of the asymmetric resonance is determined by the dark mode’s frequency and perturbed by its coupling to the bright mode. Subsequently, we fit the numerical simulation absorbance spectra in Figure 5b, according to eq 3. The fitted spectra (σt) were presented by black-dashed curves for a direct comparison shown in Figure 7 (panels a−c), where the numerical spectra made good agreement with the fitted results. To measure the 25129



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range of applications, such as surface-enhanced spectroscopy, nonlinear optics, and plasmon sensors.

the e-shape nanocavity on a dielectric layer (SiO2) coated on a gold metal substrate (as shown in Figure S3 of the Supporting Information). The extinction spectra of the e-shape nanocavity were calculated for different space layer thickness of SiO2 (from 20 to 140 nm). The results shown in Figure 8a demonstrated

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ASSOCIATED CONTENT

S Supporting Information *

Extinction spectra of nanoring plasmonics nanostructure; field enhancement of the antisymmetric modes of nanoring and corresponding charge density distrubtion of the modes of nanoring; charge density distrubtion of the nanorod, c-shape nanoring, and e-shape nanocavity for negative and positive s; and schematic diagram of e-shape nanocavity on dielectric spacer layer (SiO2) coated on gold substrate. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. *E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National High Technology Program of China under Grants 2011AA03A105, 2011AA03A103, and 2011AA03A107 and the National Natural Sciences Foundation of China under Grant 60806001. The authors thank Lina Wang for the helpful discussion.

Figure 8. (a) Reflection spectra of e-shape nanocavity on a gold substrate as a function of SiO2 dielectric spacer thickness h. (b) Field intensity enhancement plot as a function of SiO2 dielectric spacer thickness h. (c−d) Electric field distribution of nonoptimized and optimized (h = 80 nm) e-shape nanocavity.

■

that the modulation depth of the reflection spectra in the eshape nanocavity increased initially but decreased with the spacer thickness increasing. The maximum modulation depth was achieved at the spacer layer thickness of 80 nm. The field enhancement in the high-field region of the e-shape nanocavity (represented by the red dot shown in Figure S3 of the Supporting Information) was also calculated and shown in Figure 8b. With the thickness of spacer increasing, the field enhancement was also initially increased and then decreased. Furthermore, the field enhancement was also found to be maximized at the spacer layer thickness of 80 nm. This indicates that the magnitude of extinction dip is linearly proportional to field intensity enhancement, which is also found in the dipole antenna system.41 Figure 8 (panels c and d) shows the electric field intensity distributions of nonoptimized and optimized e-shape nanocavity. Compared to the nonoptimized situation, electric field intensity of the optimized e-shape nanocavity has been dramatically enhanced.

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3. CONCLUSIONS In summary, we systematically investigated a tunable Fano resonance for plasmonic nanostructure with an e-shape nanocavity, which consist of a c-shape nanoring and nanorod. The results show that the capacitive coupling between the cshape nanoring and nanorod antenna was asymmetric. The spectral positions and the modulation depths of the Fano resonances can be modulated within a wide range by changing the geometry parameters of the nanocavity. Moreover, the performance (modulation depth of spectra and near field enhancement) of the e-shape nanocavity can be further improved through optimization of the nanocavity’ radiation characteristics. Therefore, the e-shape nanocavity combining the advantages of optical tunability could be useful for a wide 25130



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