Credit: Virginia Lorenz

Steve Cundiff studies dense atomic vapors at temperatures ranging from 300-800 °C. By directing excitation laser pulses into dense vapors of potassium atoms, his group can study the signal beam generated by coherent interaction between the excitation pulses in the vapor. The method is similar to using a stroboscope, which uses pulses of ordinary light to make tennis balls appear stationary as they fly through the air. One goal of the experiments is to test an 1873 prediction of a fundamental interaction of light (known as the Lorentz-Lorenz shift) with a dense ensemble of oscillators. Preliminary results suggest that the interactions are more complicated than Hendrik Lorentz predicted more than 130 years ago.

Cundiff's group has shown that the first laser pulse synchronizes resonance frequencies of the potassium atoms' emitted light (i.e., creates coherence); additional pulses gather information about the dissipation of the coherence caused by atomic collisions. By varying the amount of time between pulses, the group can monitor what occurs as atoms approach each other, collide, and fly apart. This research is shedding light on the relationship between collisions that can be explained by classical physics and quantum level interactions.