C. J. Winta, S. Gewinner, W. Schoellkopf, M. Wolf, and A. Paarmann:
OSA Technical Digest (online) (Optical Society of America, 2016), paper FTu4A.5;
We demonstrate mid-infrared second harmonic generation spectroscopy as a novel type of phonon spectroscopy for a-quartz. The immense tunability of an infrared free-electron laser gives access to optical phonons in the range of 350-1400 cm-1.
The original publication is available by link DOI: 10.1364/CLEO_QELS.2016.FTu4A.5