Giant Pockels effect in an electrode-water interface for a “liquid” light modulator

Hayama, Daisuke; Seto, Kazuto; Yukita, Shunpei; Kobayashi, Takayoshi; Tokunaga, Eiji

doi:10.1364/osac.2.003358

Cited by 7 publications

(17 citation statements)

References 24 publications

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“…In fact, in the Pockels effect of interfacial water on transparent electrode ITO and metal electrode Pt, Y is inverted (delayed) with respect to X at frequencies of this range, as shown in Figure 11, being consistent with the impedance measurement. Note that the results in Figure 11b are the same in mechanism as the present signal in that the resonance reflectance dip is generated by coherent perfect absorption [20,21]. The real and imaginary parts are considered to be reflected in the 𝑋 and 𝑌 of the lock-in signal.…”

Section: Magnitude and Phase Of Voltage Distributed In The Electric D...mentioning

confidence: 60%

“…The interference effect appeared as a sharp spectral dip in the total reflection spectrum at the ITO-water interface, and evanescent light penetrating the water side picked up the ∆n there, causing the dip to shift spectrally. Note that the principle of this modulator is the same as Reference [15], because the mechanism of generating the sharp dip is both "coherent perfect absorption" [20,21]. Therefore, if the Pockels coefficient of water at the interface of a metal showing sharp SPP resonance is large, it would provide a unique method of light modulation because the SPP and the Pockels effect are both the interfacial effect.…”

Section: Introductionmentioning

confidence: 99%

“…However, the following can be argued modestly about the sign. It is reported that the transmission spectra (interference fringes) are blue-shifted and ∆n is negative (r 13 , r 33 > 0) for the interfacial water on the transparent oxide electrode [3,21], while the transmission spectrum is characterized by the red-shift on the Pt electrode [8], and ∆n is most likely to be positive (r 13 < 0). From this, since Ag is a noble metal as well as Pt, and it is more likely that the ∆n of the interfacial water on the Ag electrode is positive ∆n > 0 (∆n < 0) for the positive (negative) applied voltage, so that the Pockels coefficient is negative (r 33 < 0).…”

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confidence: 99%

“…Sci. 2021, 11, x FOR PEER REVIEW 14 of 17sent signal in that the resonance reflectance dip is generated by coherent perfect absorption[20,21].…”

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confidence: 99%

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Electric-Field Induced Shift in the Plasmon Resonance Due to the Interfacial Pockels Effect of Water on a Silver Surface

et al. 2021

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In the research on application of an optical modulator used for information communication, materials having a large Pockels effect, a refractive index change proportional to the electric-field, are required. It is known that the interfacial water on the surface of transparent oxide electrodes has a giant Pockels coefficient, which is an order of magnitude larger than the solid Pockels crystals practically used. It is important to know the Pockels coefficient of water on not only an oxide surface, but also a metal surface to understand the mechanism of the interfacial Pockels effect of water. However, a method has not yet been established for evaluating the coefficient of water–metal interface. Here we present an evaluation method of the Pockels coefficient of interfacial water on a metal (silver) surface from the spectral shift of the surface plasmon polariton resonance due to electric-field induced refractive index change of the interfacial water. The Pockels coefficient of interfacial water on Ag was evaluated as pm/V, without need for exact knowledge of the thickness of the interfacial layer (electric double layer of water) as long as the penetration depth of the plasmon is larger than the thickness.

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Section: Magnitude and Phase Of Voltage Distributed In The Electric D...mentioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

“…Sci. 2021, 11, x FOR PEER REVIEW 14 of 17sent signal in that the resonance reflectance dip is generated by coherent perfect absorption[20,21].…”

mentioning

confidence: 99%

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Electric-Field Induced Shift in the Plasmon Resonance Due to the Interfacial Pockels Effect of Water on a Silver Surface

et al. 2021

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“…These experimental and calculated results indicate that the refractive index is anisotropic in the direction parallel and perpendicular to the interface (see Appendix B in the Supporting Information). It is a surprising result that an anisotropic refractive index was observed in the liquid compared to the observations of SCCPA in the PVP polymer film on the MgF 2 substrate in the preceding paper 4 and in the ITO film on the glass substrate in ref 19, where the dip of ppolarization appears at shorter wavelengths than that of spolarization and is explained by an isotropic refractive index.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Observation of Coherent Perfect Absorption in Oil Film on Water Surface and Sensitive Detection of Refractive Index Anisotropy in the Film

Hasegawa,

Oi,

Yamashita

et al. 2023

Langmuir

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Sharp reflection dips of 50% were observed when white light was incident from the side of a cell on a 1 μm thick film of silicone oil (polydimethylsiloxane, PDMS, nearly transparent in visible light, with the extinction coefficient κ ≈ 0.0001) above a water surface in the cell so that the total reflection condition was satisfied at the oil-air interface. This is the first observation of a coherent perfect absorption (CPA) phenomenon in liquid. The experimental results can be reproduced by the Fresnel reflectance of the monolayer film, but the wavelength positions at which the dip appears for s-polarized and p-polarized light are reversed if the refractive index of the oil film is assumed to be isotropic. The experimental results were correctly reproduced by assuming that the extraordinary-ray refractive index (light polarized perpendicular to the interface) is 1% larger than the ordinary-ray refractive index (light polarized parallel to the interface). This indicates that the polarization dependence of the CPA phenomenon is extremely sensitive to the difference between the in-plane and out-of-plane refractive indices of the thin film.

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Voltage-induced modulation of interfacial ionic liquids measured using surface plasmon resonant grating nanostructures

Aravind,

Wang,

Cai

et al. 2024

The Journal of Chemical Physics

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We have used surface plasmon resonant metal gratings to induce and probe the dielectric response (i.e., electro-optic modulation) of ionic liquids (ILs) at electrode interfaces. Here, the cross-plane electric field at the electrode surface modulates the refractive index of the IL due to the Pockels effect. This is observed as a shift in the resonant angle of the grating (i.e., Δϕ), which can be related to the change in the local index of refraction of the electrolyte (i.e., Δnlocal). The reflection modulation of the IL is compared against a polar (D2O) and a non-polar solvent (benzene) to confirm the electro-optic origin of resonance shift. The electrostatic accumulation of ions from the IL induces local index changes to the gratings over the extent of electrical double layer (EDL) thickness. Finite difference time domain simulations are used to relate the observed shifts in the plasmon resonance and change in reflection to the change in the local index of refraction of the electrolyte and the thickness of the EDL. Simultaneously using the wavelength and intensity shift of the resonance enables us to determine both the effective thickness and Δn of the double layer. We believe that this technique can be used more broadly, allowing the dynamics associated with the potential-induced ordering and rearrangement of ionic species in electrode–solution interfaces.

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Giant Pockels effect in an electrode-water interface for a “liquid” light modulator

Cited by 7 publications

References 24 publications

Electric-Field Induced Shift in the Plasmon Resonance Due to the Interfacial Pockels Effect of Water on a Silver Surface

Electric-Field Induced Shift in the Plasmon Resonance Due to the Interfacial Pockels Effect of Water on a Silver Surface

Observation of Coherent Perfect Absorption in Oil Film on Water Surface and Sensitive Detection of Refractive Index Anisotropy in the Film

Voltage-induced modulation of interfacial ionic liquids measured using surface plasmon resonant grating nanostructures

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