Dispersion requirements in coherent frequency-to-time mapping

The frequency-to-time mapping technique (also known as the temporal far-field phenomenon) usually requires a significant amount of dispersion to stretch an ultrashort optical pulse so that the intensity profile becomes a scaled replica of its optical spectrum. In this work, we study the near-to-far-field transition and find that the far-field condition can be relaxed in some cases relevant for radio-frequency (RF) waveform generation. This observation has allowed us to achieve intensity signals with an ultrabroad RF bandwidth content.