Deflection of Ultra Slow Light by Earth Gravity on Laboratory Length Scale

The high speed of light in vacuo together with the weakness of Earth gravity rules out any experimental detection of gravitational deflection of light on the laboratory length scale. Recent advances in coherent optics that produce ultra slow light in highly dispersive media with the group velocities down to ~102 ms-1, or even less, however, open up this possibility. In this work, we present a theoretical study for a possible laboratory observation of the deflection of such an ultra slow light in the highly dispersive medium under Earth gravity. Our general relativistic calculation is based on the Gordon optical metric modified so as to include dispersion. The calculated linear vertical deflection turns out to be ~0.1 mm for a horizontal traversal of 0.1 m, and a group speed vg ~ 102 ms-1. Experimental realizability and some conceptual points involved will be briefly discussed.