  Terahertz (THz) band communications is envisioned as a key technology for
future wireless standards. Substantial progress has been made in this field,
with advances in hardware design, channel models, and signal processing.
High-rate backhaul links operating at sub-THz frequencies have been
experimentally demonstrated. However, there are inherent challenges in making
the next great leap for adopting the THz band in widespread communication
systems, such as cellular access and wireless local area networks. Primarily,
such systems have to be both: (i) wideband, to maintain desired data rate and
sensing resolution; and, more importantly, (ii) operate in the massive near
field of the high-gain devices required to overcome the propagation losses. In
this article, it is first explained why the state-of-the-art techniques from
lower frequencies, including millimeter-wave, cannot be simply repurposed to
realize THz band communication systems. Then, a vision of wavefront engineering
is presented to address these shortfalls. Further, it is illustrated how novel
implementations of specific wavefronts, such as Bessel beams and Airy beams,
offer attractive advantages in creating THz links over state-of-the-art
far-field beamforming and near-field beamfocusing techniques. The paper ends by
discussing novel problems and challenges in this new and exciting research
area.
  Index Terms - Terahertz Communications; 6G; Wavefront Engineering; Bessel
beams; Near field; Orbital Angular Momentum
