GRENOUILLE

Grating-eliminated no-nonsense observation of ultrafast incident laser light e-fields (GRENOUILLE) is an ultrashort pulse measurement technique based on frequency-resolved optical gating (FROG).

The effect of these replacements is to eliminate all sensitive alignment parameters while increasing the signal strength.

However, like the previous systems, GRENOUILLE still determines the full phase and intensity data of a pulse and produces traces identical in form to those from SHG FROG.

The effect of this element is to split the beam into two sources and superimpose the two at the focus point in the SHG crystal, thus mapping delay to the horizontal position.

The two identical beams from the biprism cross in the crystal with a delay that varies in the horizontal direction, which is effectively a self-gating process.

The second function of the SHG crystal is to act as the spectrometer by converting vertical incidence angle into wavelength.

In a normal second harmonic generation, the goal is to minimize the group-velocity mismatch (GVM) in order to maximize phase-matching bandwidth.

This is typically achieved by requiring the fundamental and second harmonic wavevectors to overlap throughout the crystal length, L. However, in a GRENOUILLE the goal is to only phasematch a portion of the pulse bandwidth in order to act as a frequency filter.

, the constraint is In addition, if the crystal is too thick, the accumulation of group-velocity dispersion (GVD) will cause excessive pulse spreading.

This means that a crystal length L will satisfy the simultaneous condition above if which is considered the fundamental relationship of the system.

From this, it can be seen that material properties and crystal dimensions will affect GRENOUILLE's temporal and spectral resolution.

To understand the performance of a given crystal, a factor, A, is introduced to the GVD and GVM conditions, which can be rearranged to get In the above equation, the TBP has been assumed to be approximately equal to 1, indicating a near-transform limited pulse.

The case where A equals 1 is considered the cutoff for satisfying the condition and is the edge of where the crystal can resolve a pulse.