ABSTRACT In this work, an experimental approach was used for measuring birefringence of thermotropic liquid crystal materials at different wavelengths in the visible region by using speckle interferometry. Also the values of the refractive indices were measured for these thermotropic liquid crystal materials in isotropic and liquid crystal phases at different wave-lengths. Temperature dependency of the refractive indices for each LC sample at certain wavelengths was investigated in the isotropic and in LC phases.
Cite this paper
T. El-Dessouki, M. Roushdy, N. Hendawy, M. Naoum and A. Zaki, "Optical Measurements of Thermotropic Liquid Crystals," Journal of Modern Physics, Vol. 4 No. 1, 2013, pp. 39-48. doi: 10.4236/jmp.2013.41008.
 A. Roshi, “Quenched Random Disorder Studies in Liquid Crystal and Aerosil Dispersions,” Faculty of the Worcester Polytechnic Institute, Worcester, 2005.
 Y. Yusril, S. Yusuke and K. Shoichi, “Birefringence Measurement of Liquid Single Crystal Elastomer Swollen with Low Molecular Weight Liquid Crystal,” Chemical Physics Letters, Vol. 382, No. 1, 2003, pp. 198-202.
 B. Badr-Eddine, H. El-Houssine, Z. Qin and V. Bruno, “An Electro-Optic Modulation Technique for Direct and Accurate Measurement of Birefringence,” Optical Communication, Vol. 221, No. 4-6, 2003, pp. 271-278.
 T. Beica, R. Moldovan, M. Tintaru, I. Enache and S. Frunza, “Measurements of Optical Anisotropy of A Calamitic Lyotropic Liquid Crystal,” Crystal Research and Technology, Vol. 39, No. 2, 2004, pp. 151-156.
 M. Manaia, A. Gharbia, J. P. Marceroub, H. T. Nguyenb and J. C. Rouillonb, “Optic and Electro-Optic Investigations on Smq, Smc_A and L Phases in Highly Chiral Compounds,” Physica B, Vol. 368, No. 1-4, 2005, pp. 168-178.
 Z. L. Cao, L. Xuan, L. F. Hu, X. H. Lu and Q. Q. Mu, “Temperature Effect on the Diffraction Efficiency of the Liquid Crystal Spatial Light Modulator,” Optics Communications, Vol. 267, No. 1, 2006, pp. 69-73.
 A. Jafari, A. Ghanadzadeh, H. Tajalli and M. Yeganeh, “Linear Optical Oarameters of a Dyed Nematic Mixture in the Presence of an ac Voltage,” Optical Materials, Vol. 29, No. 8, 2007, pp. 1004-1009.
 N. Bitri, A. Gharbi and J. P. Marcerou, “Scanning Conoscopy Measurement of the Optical Properties of Chiral Smectic Liquid Crystals,” Physica B: Condensed Matter, Vol. 403, No. 21-22, 2008, pp. 3921-3927.
 T. A. El-Dessouki, N. I. Hendawy and A. A. Zaki, “Measuring Birefringence of Curved Sheet and Single Crystals by Double-Exposure Speckle Photography,” Optics and Lasers in Engineering, Vol. 47, No. 6, 2009, pp. 622-628.
 R. I. Nessim, “Phase Behaviour of Binary Mixture of 4-Substituted Phenyl 4’-N-Alkoxybenzoates,” Liquid Crystals, Vol. 30, No. 2, 2003, pp. 211-218.
 E. Hecht and A. Zajac, “Optics,” Addison-Wesley, Reading, 1990.
 M. Francon, “Information Processing Using Speckle Patterns,” In: J. C. Dainty, Ed., Laser Speckle and Related Phenomena, Springer-Verlag, New York, 1975, pp. 171-201. doi:10.1007/BFb0111439
 L. M. Bernardo and O. D. D. Soares, “Birefringence Measurements by Double Speckle Photography,” Applied Optics, Vol. 26, 1987, pp. 769-772.
 W. A. Crossland, J. H. Morrissy and B. Needham, “Tilt Angle Measurements Of Nematic Phases Of Cyano-Biphenyls Aligned By Obliquely Evaporated Films,” Journal of Physics D: Applied Physics, Vol. 9, No. 14, 1976, p. 2001.
 T. Fujikawa, K. Hiraok, et al., “Construction of Dynamic Conoscope Observation System Using CCD Camera And Image Processor,” Japanese Journal of Applied Physics, Vol. 32, 1993, p. 985-988. doi:10.1143/JJAP.32.985