Mechanisms of the anomalous Pockels effect in bulk water

Yukita, Shunpei; Suzuki, Yuto; Shiokawa, Naoyuki; Kobayashi, Takayoshi; Tokunaga, Eiji

doi:10.1007/s10043-018-0407-6

Cited by 6 publications

(12 citation statements)

References 21 publications

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“…The fact that the Pockels coefficient of interfacial water on the Ag electrode (5 pm/V) is nearly two orders of magnitude smaller than that on the ITO transparent electrode (200 pm/V) is consistent with the previous report of the Pockels coefficient on ITO and Pt electrodes [8]. Pt and Ag are common in that both are noble metals and are robust against oxidation.…”

Section: Discussionsupporting

confidence: 91%

“…However, the microscopic physical mechanism is still unknown, and there is no theory that can predict the magnitude and sign of the Pockels coefficient. For metal electrodes, there is only an evaluation on the order of the Pockels coefficient for platinum being two orders of magnitude smaller than that of ITO [8], and a precise quantitative evaluation has not yet been performed. The reason for this is that the ∆n of interfacial water on the transparent electrode was estimated from the shift of interference fringes in the transmission spectrum of the thin transparent electrode film [2,3], while the same method cannot be used for metals because it is difficult to observe interference fringes even in thin films due to their large extinction coefficient [8].…”

Section: Introductionmentioning

confidence: 99%

“…For metal electrodes, there is only an evaluation on the order of the Pockels coefficient for platinum being two orders of magnitude smaller than that of ITO [8], and a precise quantitative evaluation has not yet been performed. The reason for this is that the ∆n of interfacial water on the transparent electrode was estimated from the shift of interference fringes in the transmission spectrum of the thin transparent electrode film [2,3], while the same method cannot be used for metals because it is difficult to observe interference fringes even in thin films due to their large extinction coefficient [8]. If we can evaluate the Pockels coefficient of water at the interface of noble metals such as silver (Ag) and platinum (Pt), it will be the key to understand the mechanism.…”

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%

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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: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…This phenomenon would not be observable in pure molecular liquids such as glycerol, in which such an ordering near an electrode is absent. However, the Pockels effect in the liquid phase has indeed been reported by Tokunaga and co-workers for water and other polar organic solvents containing electrolytes (NaCl, NaF, and LiCl) at both low (0.1 M) and high (3–4 M) concentrations. − …”

Section: Resultssupporting

confidence: 59%

Observation of the Pockels Effect in Ionic Liquids and Insights into the Length Scale of Potential-Induced Ordering

et al. 2021

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Ionic liquids (ILs) under electric fields play essential roles in the electrochemical utilization of ILs. Recently, long-range organization of ILs in the vicinity of charged (and even neutral) surfaces has been revealed, but experimental evidence for such an ordering is still limited and its spatial length scale remains controversial. Here, we use confocal Raman microspectroscopy to investigate the effect of an applied electric potential on the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and its analogues in a space-resolved manner. Much to our surprise, the observed Raman difference spectra of the ILs obtained with and without an applied potential exhibit uniform intensity changes independent of vibrational modes of cations and anions, a finding in sharp contrast with the electric field effects on molecular liquids that we have previously observed. We interpret this unexpected finding in terms of the Pockels effect that occurs as a result of a potential-induced ordering of the IL near an IL–electrode interface. The refractive index changes due to the applied potential are estimated using the experimental Raman intensity changes. The results allow us to deduce that the length scale of the ordering in the ILs is tens to hundreds of nanometers, extending more than would be expected for the electrical double layer but not as far as a micrometer scale.

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

Hayama¹,

Seto²,

Yukita³

et al. 2019

OSA Continuum

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Mechanisms of the anomalous Pockels effect in bulk water

Cited by 6 publications

References 21 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 the Pockels Effect in Ionic Liquids and Insights into the Length Scale of Potential-Induced Ordering

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

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