Carrier-Envelope-Phase Characterization Using Harmonic Spectral Interference in Mid-Infrared Laser Filament in Argon

Nonlinear self-channeling (filamentation) of intense, ultrashort laser pulses in air has been extensively studied with ultrafast, near-infrared and visible laser sources [1] . Recently these investigations advanced to longer wavelengths, as well as to the regime of few-cycle pulses, where the effects associated with the carrier-envelope phase (CEP) of the laser pulse become important. It has been shown that spectral interference in the white light generated on filamentation of an ultrafast, short-wave infrared laser source carries CEP information [2] . Here, we report using this spectral interference for single-shot characterization of the CEP of an ultrafast, mid-infrared (MIR) laser source at 3.9 µm wavelength.