Laser-Ablated Antireflective Structures for Terahertz Radiation Focusing

Numerical simulations and experimental characterization of laser-ablated anti-reflective, phase shifting and focusing structures for terahertz frequencies are presented. Nearly 90 % transmittance of silicon wafers with anti-reflective structures on both sides was confirmed experimentally within 0.5-0.6 THz frequency range. Focusing binary zone plate for 0.6 THz was produced employing phase shift differences due to the dual function antireflective layer. Close to diffraction-limited focusing performance was demonstrated thus further confirming sufficient uniformity of the structured layer for reliable phase-shifting application.