Numerical studies of the interplay between self-phase modulation and dispersion for intense plane-wave laser pulses
A computer algorithm is presented which allows simultaneous consideration of self-phase modulation and dispersion for predicting temporal shape changes during the propagation of plane-wave intense light pulses. The algorithm entails considering propagation alternately in regions where only one of the two above effects is operative. Numerical simulations of propagation in CS$sub 2$ indicate that, after sufficient travel, a shock can form on the leading edge of a mathematically smooth incident pulse. With further propagation, the entire pulse develops violent amplitude features. Impressed amplitude noise on the pulse is shown to intensify this instability. Propagation of 5-ps mode- locked dye laser pulses in CS$sub 2$-filled fibers is considered. Shocks appear at 2-m propagation if the input peak intensity is 50 MW/cm$sup 2$. Furthermore, attenuation present in the fibers tends to stabilize the shape of the shock as it forms. For optimal compression more dispersive delay is required in a compressor than would have been needed in the absence of CS$sub 2$ dispersion. Compression of pulses emanating from the CS$sub 2$-filled fibers was calculated. The subsequent compressed pulses are not much shorter than the temporal shock which had formed on the pulse prior to compression. Propagation distances in such experiments should thus be kept below the shock distance. The simulation of pulse propagation in Nd : glass laser amplifier chains is also studied, with nonlinearity and dispersion taken into account. In the absence of gain, pulses temporally broaden and flatten because the glass dispersion is the wrong sign to compress the chirp which develops at the temporal center of the pulse. In pumped amplifiers a sharp temporal spike forms at the center because the chirp swings the pulse center frequency through the center frequency of the amplifying transition at that time. Under typical operating conditions, pulses are relatively stable to amplitude modulation.
- Research Organization:
- Los Alamos Scientific Lab., NM
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-028868
- OSTI ID:
- 4074455
- Journal Information:
- J. Appl. Phys., v. 46, no. 11, pp. 4921-4934, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
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