Improving depth-of field in broadband THz beams using nondiffractive Bessel beams

We report new results related to imaging using broadband Bessel-like beams at the terahertz (THz) domain that were generated by use of axicons and pulsed THz radiation emitting at a bandwidth 0.1 to 1 THz. Such Bessel-like beams exhibit an invariant line of focus with an extended length compared to Gaussian-beams Rayleigh range, which enables imaging through the extended length. We demonstrate this imaging property using a resolution target illuminated by broadband-THz beams and show an improvement by a factor of 3.5 in imaging depth while using Bessel-like beams over Gaussian beams. Our results highlight the potential in using broadband THz radiation together with nondiffractive Bessel beams to significantly improve spatial separation over deep view.