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Role of the temporal profile of femtosecond lasers of two different colours in holography

The role of the temporal profile of femtosecond lasers in obtaining the holograms is uncovered when two lasers of different colours are used to produce the fringes and recording of holograms. It was shown that the contrast of the time average interference pattern of two short light pulses (pulse duration T) of different colours is remarkably high for frequency detuning (see Odoulov S. et al., Nat. Commun., 6 (2015) 5866). However, we prove that such a continuous range of frequency detuning is not possible but null regions develop and frequency bands are observed for realizing holograms if there is a deviation of the lasers from their Gaussian profiles. The increased pulse duration leads to the generation of additional frequency bands and their narrowing along with higher modulation depth. A shifting of the null regions is noticed for the lasers having different skewness and/or pulse duration.