An In-Situ Method for the Reconstruction of Ultrashort and Ultrabroadband Synthesized Light Transients

We present a novel method for the reconstruction of ultrashort and ultrabroadband synthesized light transients generated by a parametric waveform synthesizer [1]. Our method relies on the measurement of the third-order nonlinear response (
$S_{NL}$
) of a noble gas target normally used for high-harmonic generation (1 mm length at 0.1-1 bar) while scanning the relative delay
$\tau$
between the two constituent ultrabroadband pulses
$(E_{1}(t)$
and
$E_{2}(t))$
that are synthesized (c.f. Fig. 1(d)). The recorded spectrogram can be described by
$S_{NL}(f,\tau)\propto T(f)\vert FT[(E_{1}(t)+E_{2}(t+\tau))^{3}]\vert^{2}$
, where
$T(f)$
describes a spectral transfer function and
$FT$
denotes the Fourier transform.