Ultrahigh-speed photography of picosecond light pulses

A new technique for the display of picosecond light pulses is presented. Ultrashort (6 ps) green light pulses passing through a light-scattering medium are photographed from the side by a camera positioned behind a shutter of 10-ps framing time. The shutter is an ultrafast Kerr cell driven by infrared pulses 8 ps in duration. Color photographs show a bright spot on a dark background, revealing the unambiguous presence of well-isolated picosecond light pulses. The shape of the spot is the result of a convolution involving the three-dimensional shape of the green pulse and the time transmission function of the shutter, this function being dictated by the shape of the infrared pulse. The experiment indicates that a new technique for visualizing light pulses consists in simply observing their flight through a scattering medium from behind an ultrafast shutter having a framing time equal to the time resolution desired. The new technique has many advantages over the two-photon fluorescence display technique, such as higher sensitivity, wider spectral range, and easier interpretation. The ultrafast camera also can be used for the photographic measurement of ultrashort relaxation times in dielectrics and in fluorescent dyes.