Broadband Anti-Reflection coating for THz waves developed with Si nanoparticle-polymer composite material

THz optical elements, typically made of silicon (Si), suffer from large reflection due to the large gap in refractive index at the interface between Si and air. In this research, anti-reflection (AR) coating for THz region using polymer and Si nanoparticle (SiNP) composite was developed to minimize the reflection loss. Low absorbance and small diameter of SiNPs allowed the THz waves to transmit the composite without absorption and scattering. The AR layer coated on a THz optical element successfully demonstrated transmittance exceeding 90 % in amplitude as wide as Δf= 0.8 THz 1 THz.