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Doctoral Thesis
DOI
10.11606/T.43.2002.tde-18022014-170116
Document
Author
Full name
Fabio Luiz Sant'Anna Cuppo
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2002
Supervisor
Committee
Figueiredo Neto, Antonio Martins (President)
Carvalho, Isabel Cristina dos Santos
Evangelista, Luiz Roberto
Nussenzveig, Paulo Alberto
Zilio, Sérgio Carlos
Title in Portuguese
Estudo da não-linearidade óptica de origem térmica em cristais líquidos liotrópicos e seu comportamento nas vizinhanças de transições de fase
Keywords in Portuguese
Cristais líquidos
Óptica não-linear
Propriedades térmicas
Transições de fases
Abstract in Portuguese
Este trabalho visou o estudo da resposta óptica não-linear de cristais líquidos liotrópicos nas fases isotrópicas e nemática calamítica e nas vizinhanças das transições de fase nemática calamítica isotrópica e nemática calamítica nemática biaxial. Para este estudo foi utilizada, fundamentalmente, a técnica de varredura Z. Os resultados obtidos indicam que o efeito não-linear em cristais líquidos liotrópicos esta ligado à presença de micelas na mistura e que a anisometria de micela tem influencia na resposta observada. Foi observado ainda que a presença de ferrofluido na mistura, mesmo em pequenas quantidades, causa um grande aumento na absorção óptica da amostra e consequentemente da resposta não-linear. O comportamento do índice de refração não-linear (n IND.2) em função da temperatura nas vizinhanças da transição da fase nemática calamítica para nemática biaxial apresenta um crescimento expressivo de (n IND.2). Nas vizinhanças da transição nemática calamítica para isotrópica esse efeito não foi observado.
Title in English
Study of optical nonlinearity of thermal origin in lyotropic liquid crystals and its behavior in the vicinity of phase transitions.
Keywords in English
Liquid crystals
Non-linear optics
Phase transitions
Thermal properties
Abstract in English
This work has been focused on the study of the optical nonlinear response of lyotropic liquid crystals in the isotropic and nematic calamitic phases and in the neighborhood of the nematic calamitic isotropic and nematic calamitic nematic biaxial phase transitions. The basic technique we used is Z-scan. The results obtained indicated that the nonlinear effect in lyotropic liquid crystals is related to the presence of micelles in the mixture and the micelle anisotropy has influence on the observed response. Is has also been observed that the presence of ferrofluid in the mixture, even in small quantities, causes a large raise in the sample optical absorption and consequently in the nonlinear response. The behavior of the nonlinear refractive index (n IND.2) as function of temperature in the neighborhood of the nematic calamitic to nematic biaxial phase transition shows as expressive n IND.2 raise. This behavior has not been observed in the neighborhood of the nematic calamitic to isotropic phase transition.
 
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37583Cuppo.pdf (65.02 Mbytes)
Publishing Date
2014-02-18
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • ALVES, S, CUPPO, F. L. S., and Neto, A.M.F. Determination of the nonlinear refractive index of lyotropic mixtures with and without ferrofluid doping: a time-resolved Z-scan experiment in millisecond time scales [doi:10.1364/JOSAB.23.000067]. Journal of the Optical Society of America. B, Optical physics [online], 2006, vol. 23, p. 67-74.
  • ALVES, S., et al. Thermodiffusion of magnetite nanoparticles in ferrofluid-doped micellar systems and in ferrofluids investigated by using the single-beam Z-scan technique [doi:10.1364/JOSAB.23.002328]. Journal of the Optical Society of America. B, Optical physics [online], 2006, vol. 23, p. 2328-2335.
  • CUPPO, F L S, GOMEZ, S L, and Neto, A.M.F. Behavior of the nonlinear refractive indices and birefringence in the neighborhood of first- and second-order phase transitions in lyotrtropic liquid crystals. Physical Review E - Statistical Physics, Plasmas, Fluids and Related Interdisciplinary Topics, 2003, vol. 67.
  • CUPPO, F L S, GOMEZ, S L, and Neto, A.M.F. Effect of the concentration of magnetic grains on the linear-optical-absorbance coefficient of ferrofluid-doped lyotropic mesophases: Deviation from the Beer-Lambert law [doi:10.1140/epje/i2003-10076-8]. European Journal of Physics [online], 2004, vol. E13, p. 327-333.
  • CUPPO, F. L. S., et al. Thermal-lens model compared with the Sheik-Bahae formalism in interpreting Z-Scan experiments on lyotropic liquid crystals [doi:10.1364/JOSAB.19.001342]. Journal of the Optical Society of America. B, Optical physics [online], 2002, vol. 19, p. 1342-1348.
  • CUPPO, F. L. S., and Neto, A.M.F. Thermal and nonlinear optical properties of Potassium laurate/water solutions at amphiphilic concentrations around the critical micellar concentration: a laser Gaussian single beam experiment in millisecond timescales [doi:10.1021/la026267o]. Langmuir [online], 2002, vol. 18, p. 9647-9653.
  • GÓMEZ, S L, CUPPO, F L S, and Neto, A.M.F. Nonlinear optical properties of liquid crystals probed by Z-scan technique [doi:10.1590/S0103-97332003000400035]. Brazilian Journal of Physics [online], 2003, vol. 33, p. 813-820.
  • GOMÉZ, S. L., et al. Z-scan measurement of the nonlinear refractive indices of micellar lyotropic liquid crystals with and without the ferrofluid doping [doi:10.1103/PhysRevE.59.3059]. PHYSICAL REVIEW E [online], 1999, vol. 59, nº 3, p. 3059-3063.
  • GOMEZ, S., et al. Z-Scan measurement of the nonlinear refractive indices of micellar lyotropic liquid crystals with and without the ferrofluid doping. In Europeam Liquid Crystal Conference 99, Crete, Grécia, 1999. Book of abstracts Hersonissos, University of Patras, 1999., 1999. Abstract.
  • ALVES, S, et al. Thermodiffussion of magnetite nanoparticles in ferrofluid-doped micellar systems and in ferrofluids. In 7th International Meeting on Thermodiffusion (IMT7), San Sebastian, 2006. IMT7 Thermodiffusion., 2006. Abstract.
  • CUPPO, F L S, and Neto, A.M.F. Nonlinear optical properties of the potassium laurate/water solutions at amphiphilic concentrations around the critical micellar concentration: a laser Gaussian single beam experiment. In XXV Encontro Nacional de Física da Matéria Condensada, Caxambu, 2002. Resumos São Paulo, 2002., 2002. Abstract.
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