Noncollinear Electro-Optic Sampling of Terahertz Waves in a Thick GaAs Crystal

In this paper, we propose and experimentally demonstrate noncollinear EO sampling of terahertz pulses with a femtosecond fiber laser in cm-thick GaAs crystals. This technique provides more than an order of magnitude improvement in spectral resolution and a significant increase in efficiency as compared to previously used collinear EO sampling in mm- and sub-mm-thick GaAs crystals. The optimal incidence angle of the probe beam on the crystal is found to be 42 $^\circ$ –50 $^\circ$ and the optimal crystal thickness is ${\sim}{\hbox{1}}{\hbox{--}}{\hbox{3}}$ cm.