Characterization of mid-infrared femtosecond pulses [Invited]

We review different methods for characterizing mid-infrared femtosecond pulses, including linear methods such as electro-optic sampling, time-and frequency-domain interferometry and nonlinear self-referenced methods such as frequency-resolved optical gating (FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). Of particular interest are methods based on upconversion through non-linear mixing with chirped 800 nm pulses, enabling a complete measurement of mid-infrared pulses with visible-light spectrometers.