Accession Number : ADP006784

Title :   Spectral Pulse Distortion from Two-Beam Coupling of Sub-Picosecond Pulses in a Photorefractive Crystal,

Corporate Author : UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES

Personal Author(s) : Yao, X. Steve ; Feinberg, Jack

Report Date : 22 MAY 1992

Pagination or Media Count : 4

Abstract : Consider the coupling between two trains of mode-locked pulses in a photorefractive crystal. Let each optical pulse be so weak that it takes a large number of pulses to built up a quasi-steady-state refractive-index grating in the crystal. In this case the shape of the pulses will change as the result of beam coupling. The temporal pulse shape changes for two reasons. First, interference between the diffracted pulse and the transmitted pulse alters the pulse shape, as shown. Second, only a portion of each pulse's full frequency spectrum is diffracted by the volume photorefractive grating. In the simplest case, in which the laser pulses are long enough so that they can be considered quasi-monochromatic, there is only one photorefractive grating formed in the crystal, and its grating wavevector is k=2(Omega/c) sin 2 theta. All of the frequency components in each pulse will be perfectly phase matched to this grating. In Eq(l), omega O is the center frequency of the laser pulses, c is the speed of light and 20 is the external crossing angle between the two interfering beams.

Descriptors :   *LIGHT PULSES, DIFFRACTION, ANGLES, COUPLINGS, CROSSINGS, CRYSTALS, LASERS, INTERFERENCE, REFRACTIVE INDEX, SHAPE, STEADY STATE, VELOCITY, VOLUME, REFRACTION, SYMPOSIA.

Subject Categories : Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE