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
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 νexp =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 νtheor=5.7 Hz, is in quite good agreement with the measured value.
PACS: 78.20.Nv – Thermooptical and photothermal effects / 61.30.Gd – Orientational order of liquid crystals; electric and magnetic field effects on order / 42.65.-k – Nonlinear optics
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2007