Far-infrared second-harmonic generation and pulse characterization with the organic salt DAST

We generated the second harmonics of pulses in the far-infrared region (30-55 mu m), using the organic salt dimethylamino-4-N-methylstilbazolium tosylate (DAST). We demonstrate that DAST can be used to characterize ultrashort pulses in a spectral region where no other materials are available. To illustrate the need for such characterizations, we show the effects of propagation through air on the shape of ultrashort far-infrared pulses. (C) 1998 Optical Society of America.