Overview: In this chapter we briefly investigate atmospheric effects on ultrashort pulses, i.e., on the order of femto-seconds. Longer pulses (e.g., picosecond pulses) can usually be modeled as if they were continuous wave (CW) signals during the time when the pulse is transmitted. However, this is not the case for ultrashort pulses.
Our treatment here is limited to temporal pulse spreading in the near field and far field, and to far-field temporal scintillations. Because of the increased bandwidth associated with short pulses, much of the analysis has to be performed in the frequency domain. This requires development of the two-frequency mutual coherence function and the four-frequency cross-coherence function.
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