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Dielectric and flexoelectric oscillations in PDLC studied by flexoelectric spectroscopy and laser light diffraction

A. G. PETROV1,* , Y. MARINOV1, S. D’ELIA2, S. MARINO2, C. VERSACE2, N. SCARAMUZZA2

Affiliation

  1. Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria
  2. LICRYL (CNR-INFM) and Center of Excellence CEMIF. CAL, Dipartimento di Fisica, Università degli Studi della Calabria, Ponte P. Bucci, Cubo 31C, 87036 Rende (CS), Italy

Abstract

Nematic droplets of variable size of E7 were dispersed in a photopolymer NOA65 matrix by the method of UV photopolymerization-induced phase separation. Dielectric and flexoelectric oscillation of the director orientation in the droplets were excited by an ac driving voltage in the range 1Hz to 3 kHz. Both thelinear and quadratic electro-optical response of the PDLC films were studied by the flexoelectric spectroscopy method and by laser light diffraction. The temperature and voltage dependence of the 1st and 2nd harmonic electro-optic spectra (amplitude and phase of the transmitted light vs frequency) were obtained, and strikingly deep minima in all spectra were found. These minima were interpreted as resulted from a spatial filtering (i.e. selective diffraction) of the time-modulated components of the transmitted light..

Keywords

Polymer dispersed liquid crystals, Flexoelectric spectroscopy, Diffraction, Spatial filtering of time modulated light beams.

Submitted at: Nov. 1, 2006
Accepted at: Feb. 15, 2007

Citation

A. G. PETROV, Y. MARINOV, S. D’ELIA, S. MARINO, C. VERSACE, N. SCARAMUZZA, Dielectric and flexoelectric oscillations in PDLC studied by flexoelectric spectroscopy and laser light diffraction, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 2, pp. 420-423 (2007)