Japanese scientists record 3-D movie of femtosecond pulse propagation (WATCH VIDEO)

November 30, 2007, Kyoto, Japan--For the first time, three-dimensional (3-D) images of femtosecond light pulse propagation have been observed and recorded by researchers at the Kyoto Institute of Technology. The continuously moving pictures are produced using holographic light-in-flight techniques and enable the temporal and spatial analysis of femtosecond pulses for improving studies of ultrafast phenomena.

In the experiment, the researchers used gelatin as a moderate 3-D scattering medium to visualize the path of light propagating within it. When an ultrashort pulsed laser is used in the holographic recording setup, interference fringes are recorded only where the object pulse--scattered by the gelatin--and the reference pulse arrive simultaneously in the recording material. Because the reference pulse obliquely illuminates the gelatin, the arrival time of the reference pulse at each point in the gelatin is different; therefore, a time-lapse image of the object is recorded along the lateral direction of the holographic plate. When the hologram is illuminated with a continuous light wave, each portion of the holographic image reconstructs the light pulse at a different point in time. By moving the point of observation along the lateral direction of the hologram, the temporally continuous moving picture of the image of the ultrashort light pulse can be observed.

To demonstrate 3-D imaging for a femtosecond pulse, a moving picture of a pulse as it converges and diverges through a convex lens was recorded (WATCH VIDEO). The research is documented in the October 29 issue of Optics Express and will also appear in the January issue of Laser Focus World magazine.