  The polarization and orbital angular momentum properties of light are of
great importance in optical science and technology in the fields of high
precision optical measurements and high capacity and high speed optical
communications. Here we show, a totally new method, based on a combination of
these two properties and using the thermal dispersion and electro-optical
effect of birefringent crystals, the construction of a simple and robust scheme
to rotate a light beam like a fan. Using a computer-based digital image
processing technique, we determine the temperature and the thermal dispersion
difference of the crystal with high resolution. We also use the rotation
phenomenon to realize thermo-optic and electro-optic switches. The basic
operating principles for measurement and switching processes are presented in
detail. The methods developed here will have wide practical applicability in
various fields, including remote sensing, materials science and optical
communication networks.
