We present a simple method to generate mid-infrared photon echoes, using parametrically downconverted incoherent light. The photon echoes generated in this way enable the study of the dynamics of vibrations in the 1.5-4.0 µm wavelength region with subpicosecond time resolution.

Laser Chem.
Ultrafast Spectroscopy

Woutersen, S., Bonn, M., Emmerichs, U., & Bakker, H. (1999). Incoherent mid-infrared photon echoes with parametrically downconverted light. Laser Chem., 19, 123–126.