Electrooptic effect of water in electric double layer at interface of GaN electrode

Hironori Kanemaru, Yugo Nosaka, Akira Hirako, Kazuhiro Ohkawa, Takayoshi Kobayashi, Eiji Tokunaga*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


We determined the Pockels constant of water in the electric double layer (EDL) at the GaN electrode interface. For a positive (negative) bias, the difference transmittance showed a blue (red) shift in the interference fringes in the visible. This was caused by a negative (positive) refractive index change both in the EDL of water and in the space charge layer (SCL) of the GaN. The latter was associated with the blue shift in the absorption edge in the UV due to the band population effect in the GaN. The voltage drops took place within the interfacial layer at a ratio of about 3: 1 for the SCL vs EDL at the modulation frequency of f = 20 Hz, estimated from the frequency dependence of the impedance. The Pockels constant of water in the EDL was determined to be r13 = 0:63 × 100 pm/V for the GaN electrodes. This is three times smaller than that at the surface of the indium tin oxide (ITO) electrode.

Original languageEnglish (US)
Pages (from-to)352-356
Number of pages5
JournalOptical Review
Issue number3
StatePublished - 2010
Externally publishedYes


  • Band population effect
  • Electric double layer
  • Electroabsorption spectroscopy
  • GaN
  • Liquid-solid interface
  • Optical nonlinearity
  • Pockels effect
  • Refractive index
  • Space charge layer
  • Water

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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