It is widely believed that the velocity of information νi encoded on an optical pulse is equal to the group velocity νg, at least when νg is less than the speed of light in vacuum c. On the other hand, several authors suggest that νi = c, although the size of the signal traveling at this velocity may be small, thereby making it difficult to measure. Here, we measure νi for pulses propagating through a resonant "slow-light" medium where νg ≈ 0.006c. We find νi ≈ 1.03c-0.25c+0.49c, or that νi χ 168νg clearly demonstrating that the speed of information cannot be generally described by νg, but is characterized by its own velocity.
ASJC Scopus subject areas
- Physics and Astronomy(all)