Liquid crystal lab1
Among the many interesting properties of liquid crystals, optical birefringence ( ) is probably one of the most important. It is the basis of liquid crystals display (LCD) as well as other device application. in this lab we have got a experimental set up used to measure the electrically induced kerr constant (EOKE). All measurements of the Kerr constant were made using the nulled intensity method. In this method. The polarizer and analyzer were Glan–Thompson double refraction type prisms of commercial origin and adjusted such that they crossed each other, making an angle 45° with respect to the applied AC field (1 kHz). A spectra physics He–Ne laser emitting at a wavelength of 632.8 nm with a power of 5 mW was used as a probe beam The estimated accuracy in the measurement of temperature is ± 0.05 °C. A photomultiplier tube, type E.M.I. 9816B is used as light photo detector and the output has been fed to a digital storage oscilloscope (Tektronix 300 MHz, model TDS3032B). The electric field is generated by means of a high-voltage power supply that was applied, as a short duration rectangular shaped pulse from a pulse generator, to the electrodes of the Kerr cell.
Results : The linear dependence of (T - T*)-1 on the Kerr constant is found to be in good agreement with the predications of the Landau-De Gennes model. The first order phase transition temperatures and susceptibility values were determined for these.
Publications : H. tajalli , A.Ghannadzadeh , H. khoshsima , A. Vahedi.
Static Efector- optic kerr effect in a novel nematic liquid Crystal.
The 11th Annual Conference on optics 8 photonic faser 8 plasma Reseacrch Institute , Shaid Beheshti university , Theran , iran , 2-3 Februay , 2005.
H. Khoshsima, H.Tajalli, A.Ghanadzadeh, R. Dabrowski, J. Phys. D: 39, 1495, (2006).