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

Yurina Nishi, Ryosuke Watanabe, Subaru Sasaki, Akihiro Okada, Keisuke Seto, Takayoshi Kobayashi, Eiji Tokunaga*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


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 |r33|=5 +/- 1 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.

Original languageAmerican English
Article number2152
Number of pages17
JournalApplied sciences-Basel
Issue number5
StatePublished - Mar 2021


  • Pockels effect
  • surface plasmon polariton
  • water
  • interface
  • electric double layer
  • electro-modulation spectroscopy
  • silver
  • penetration depth
  • attenuated total reflection
  • optical modulation


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