Eur. Phys. J. B 55, 411-418 (2007)
https://doi.org/10.1140/epjb/e2007-00081-y

Thermally induced effects on the diffraction pattern of a dye doped nematic film

¹ Departamento de Física Química, Instituto de Física, Universidad Nacional Autónoma de México, Apdo. Postal 20–364, 01000 México, D. F., Mexico
² Departamento de Materia Condensada, Instituto de Física, Universidad Nacional Autónoma de México, Apdo. Postal 20–364, 01000 México, D. F., Mexico
³ Centro de Investigación en Polímeros, COMEX, Marcos Lobatón No. 2, 55885 Tepexpan, Edo. de México, Mexico

Corresponding author: ^a zepeda@fisica.unam.mx

Received: 12 December 2006
Published online: 22 March 2007

Abstract

We investigate the effects produced on the diffraction pattern of a dyed nematic thin film under the action of an optical field and a low frequency AC electric field. For a homeotropically aligned mixture of the nematic E7 doped with a dichroic dye, a sequence of dynamical regimes of the far field diffraction pattern is observed. For specific values of the beam's power, frequency and amplitude of the AC field, a uniform steady rotational motion (SR) of the pattern sets in with a measured angular velocity ν_exp =2.58 Hz. To account for this and other observed features of the diffraction pattern an analytical model is proposed. This allows us to describe quantitatively the reorientation of the film, to calculate some specific structural features of the diffraction pattern, as well as its angular velocity. We find that the predicted angular velocity ν_theor=5.7 Hz, is in quite good agreement with the measured value.