The zinc blend nonlinear crystal
of zinc telluride (ZnTe) is currently
one of the most commonly used electro-optical material for terahertz
(THz) probe and imaging. We report herein how to engineer the surface
behavior of a ZnTe single crystal to design subwavelength structures
(SWSs) for enhancing ultrabroadband transmission. Polystyrene (PS)
nanoparticle monolayers with a maximum coverage of 85.2% were produced
on the ZnTe crystal by an eccentric spin-coating technique combined
with surface wettability engineering. Subsequently, the well-defined
conical SWS arrays were fabricated on the ZnTe crystal by reactive
ion etching over the PS monolayer template, with the size of the SWS
arrays customized by optimizing the etching process. Finally, we demonstrated
ultrabroadband antireflection on the surface structured ZnTe crystals
in the visible-near-infrared, infrared, and terahertz regions with
transmittance increase of 11.6%, 10.0%, and 24.8%, which are attributed
to the decrease of surface Fresnel reflection by SWS. Notably, in
0.2–1.0 THz, the transmittance reached over 70%. Our work provides
a new strategy to enhance the THz generation efficiency and detection
sensitivity based on ZnTe crystals by surface engineering.