Femtosecond diffracting Fourier-transform infrared interferometer.

We have developed a new scheme of Fourier-transform spectroscopy in the mid and the far infrared. The method relies on an interferometer in the visible or the near infrared, providing a sequence of two femtosecond pulses, which in turn generate a sequence of infrared pulses. The geometrical properties of the different diffracted infrared waves are used to isolate the relevant signal. An experimental demonstration is shown in the mid infrared by use of optical rectification of near-infrared 15-fs pulses.