Nonlinear optical properties of Langmuir-Blodgett monolayers: Local-field effects

Gerard Cnossen, Karel E. Drabe, Douwe A. Wiersma

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Abstract

Detailed measurements of the macroscopic second-order optical nonlinearity chi(2) (2-omega,omega,omega) of Langmuir-Blodgett dye-doped monolayers are reported. The observed deviations from a linear behavior of chi-(2) with increasing surface density are shown to be due to local-field effects. In order to calculate these local-field factors for disordered systems, a novel Monte Carlo type calculation is introduced. This calculation not only accounts for density variations in the monolayers but also incorporates the effect of off-diagonal elements of the (microscopic) linear susceptibility tensor. Quantitative agreement is found between the calculations and the experimental results using only the molecular hyperpolarizability as a free parameter. A method is presented to determine the tilt angle of the chromophores in Langmuir-Blodgett monolayers from the anisotropy of the linear absorption. The tilt angle determined this way is in excellent agreement with a determination by second-harmonic generation.
Original languageEnglish
Pages (from-to)4512-4524
Number of pages13
JournalThe Journal of Chemical Physics
Volume97
Issue number6
DOIs
Publication statusPublished - 15-Sep-1992

Keywords

  • 2ND HARMONIC-GENERATION
  • 2ND-HARMONIC GENERATION
  • MOLECULAR-ORIENTATION
  • SPONTANEOUS EMISSION
  • DISTANCE DEPENDENCE
  • ADSORBED OVERLAYERS
  • ORGANIC-MOLECULES
  • FATTY-ACID
  • HEMICYANINE
  • ENHANCEMENT

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