Abstract

Several opto-electronic techniques utilizing femtosecond laser pulses have been recently developed to generate broadband THz pulses in free space [1-3]. One method is the use of high speed photoconducting micro-strip antennae [2]. Our approach is the optical rectification of fs-laser pulses in a nonlinear organic crystal. We use the organic salt dimethyl amino 4-N-methylstilbazolium tosylate (DAST) because of its high nonlinear optical susceptibility χ⁽²⁾. The source of the ultrashort optical pulses was a cw-Ar⁺-laser pumped, mode-locked Ti:sapphire laser with a repetition rate of 76 MHz and a FWHM of 100 fs at a central wavelength of 850 nm. The duration of the pulses could be varied by means of an external group velocity dispersion control consisting of a prism pair. The laser pulses were focussed on the DAST crystal.

© 1996 IEEE