Picosecond Light Pulse Display Using Two Different Optical Frequencies

A new technique for the display and measurement of picosecond light pulses is demonstrated. Two picosecond pulses, of different optical frequencies, are sent on a collision course in a liquid. They produce strong two-photon fluorescence only in the region where they overlap. This results in the direct display of the pulse shapes over a very weak background. In a different arrangement, the two pulses enter the liquid collinearly and simultaneously, and initially generate strong two-photon fluorescence. Subsequently, as the pulses propagate through the liquid, dispersion causes one pulse to overtake the other and the two-photon fluorescence diminishes. This results in a magnified display of the pulses.