Ultrabroadband polarization analysis of terahertz pulses.

We describe the characteristics of a sensitive photoconductive detector that simultaneously measures orthogonal electric field components of electromagnetic transients with bandwidths up to 30 THz. The device consists of an As(+) implanted GaAs photoconducting region at the centre of a pair of perpendicular bow-tie antennas. The performance is illustrated by studies of optical rectification in GaSe, retardation in a birefringent polymer film and THz emission from impulsively excited optical phonons in GaN.