Effects of spatial fine structure on a femtosecond-order optical pulse are numerically studied by using nondispersive and linear dielectric diffraction gratings in the resonance domain. Whereas a pulse longer than 100 fs is expected to behave the same as a continuous wave, the distribution of energy into each diffraction order deviates gradually for shorter pulses. This is due to the wide spectral profile of the pulsed wave. Overlap of adjacent diffraction orders will also occur for a pulse shorter than 5 fs. Therefore extra attention should be paid to designing optical elements based on diffractive structure for use with ultra-short pulsed waves.
© 1999 Optical Society of America
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