Chemical sensing plate with a laser-terahertz monitoring system

Toshihiko Kiwa, Junichi Kondo, Shohei Oka, Iwao Kawayama, Hironobu Yamada, Masayoshi Tonouchi, Keiji Tsukada

Research output: Contribution to journalArticlepeer-review

66 Citations (Scopus)


A new type of laser-terahertz emission system for noncontact investigations of chemical solutions has been developed. The system monitors terahertz emission from a sensing plate, which consists of silicon oxide and silicon thin film layers on a sapphire substrate. Sensing of chemical solutions with pH values between 1.68 and 10.01 was demonstrated. The amplitude of the terahertz emission from the sensing plate increased with increasing pH value. This change in the amplitude was caused by a change in the depletion layers of the silicon thin film when protons were adsorbed on the surface of the sensing plate. This study demonstrates that full noncontact monitoring of chemical solutions is possible using the laserterahertz emission system.

Original languageEnglish
Pages (from-to)3324-3327
Number of pages4
JournalApplied Optics
Issue number18
Publication statusPublished - Jun 20 2008

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering (miscellaneous)
  • Electrical and Electronic Engineering


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