Figure 1

Schematic of the experimental setup. Initial pulses are provided by a Kerr-lens-mode-locked master oscillator, and temporally compressed in three stages, each consisting of a multi-pass self-phase-modulation cell followed by chirped mirrors. After nonlinear compression, the spectrally-filtered (SF) blue part of the near-infrared (NIR) is used to generate an error signal for intensity noise suppression with an acousto-optic-modulator (AOM)-based active stabilisation. The compressed NIR pulses drive IPDFG in a LiGaS₂ (LGS) crystal. The NIR pulses are split from the emerging MIR beam with a dichroic mirror (DM), attenuated, temporally recompressed and used as gate pulses for EOS detection. Their envelope provides the temporal reference for the measurement. An auxiliary laser for interferometric delay tracking (IDT), coupled in at the DM, co-propagates along the NIR and MIR arms towards the EOS detection; t, time; I, intensity; λ, wavelength; PD, photodiode; Ge, germanium; GaSe, gallium selenide; SF, spectral filter; QWP, quarter-wave plate; WP, Wollaston prism; BPD, balanced photodiode.