Three-dimensional direct observation of Gouy phase shift in a terajet produced by a dielectric cuboid

The generation of the terajet at the terahertz (THz) frequency with the capability of subwavelength beam-compression has been attracting increasing research interest, as did the generation of the nanojet at the optical frequency. In particular, a terajet generated from a dielectric cuboid was not previously studied experimentally in the THz region. We here experimentally demonstrate three-dimensional visualizations and characterization of a terajet generated from a dielectric cuboid with a refractive index of n = 1.46 at 125GHz. The subwavelength compressed beam and the Gouy phase shift phenomena of the terajet are directly observed. It is also found out that a calculation model of Gouy phase shift based on focused Gaussian beam by a lens cannot explain the Gouy phase shift of compressed beam by the terajet. The intensity enhancement of about 7.4 dB and full width at half maximum of 0.6 lambda are obtained at the distance 0.5 lambda from the cuboid. Published by AIP Publishing.