Scale ranging with subpsec pulses of THz radiation

Here we describe the use of optoelectronic techniques to generate single cycle pulses of freely propagating THz radiation, and thereby demonstrate ultrawide bandwidth scattering from simple geometrical objects. These pulses are the best approximation to impulse excitation ever used in ranging studies. The absolute bandwith is also larger than any other previously reported. The relatively short wavelengths of the THz pulse permit target features of less than 1 mm to be observed, making this technique ideal for scale ranging measurements since realistic target to wavelength ratios can be maintained. Furthermore, the measurement window achieved by the optolectronic gating technique enables only the scattered signal from the target to be detected, providing background free measurements.