  Ultra-fast laser pulses have made possible the study of extreme nonlinear
processes. Many of these experiments however require a full characterization of
the electric field, which typically requires a separate parametric optical
process. As the central wavelength range of new sources continues to increase
so too does the need for nonlinear crystals suited for characterizing these
differing wavelengths. Here we report on the use of polycrystalline Zinc
Selenide as a universal nonlinear crystal in the frequency resolved optical
gating characterization technique from the near to long-wavelength infrared,
capable of phase matching second-harmonic generation and sum-frequency
generation over a decade of bandwidth, as well as ultra-broadband pulses, all
of which being crystal orientation and input polarization independent. With the
majority of ultra-fast laser sources being in this span of wavelengths, this
work demonstrates a greatly simplified approach towards ultra-fast pulse
characterization in the mid to long-wavelength infrared.
