Controllable enhanced dragging of light in ultradispersive media

We have theoretically demonstrated an enhanced Fizeau effect due to dragging the light that occurs when the group velocity of light is ultraslow. The proposed experiment can be done in a cell of atomic Rb vapor under conditions such that the group velocity of light is of the order of a few hundred meters per second. We show theoretically that higher-order dispersion can influence the Fizeau effect and can be observed experimentally. It has been shown that the change of phase is sensitive to the motion of the cell with the speed of the order of 10(-3) cm/s and for possible displacements as small as 10 angstrom. The enhanced dragging effect can be applied for position control, detection of slow mechanical motion, and efficient modulators of light.