Robust terahertz polarizers with high transmittance at selected frequencies through Si wafer bonding technologies.

Terahertz (THz) polarizers with robust structure and high transmittance are demonstrated using 3D-integrated circuit (IC) technologies. A Cu wire-grid polarizer is sealed and well protected by Si-bonded wafers through a low-temperature eutectic bonding method. Deep reactive-ion etching is used to fabricate the anti-reflection (AR) layers on outward surfaces of bonded wafers. The extinction ratio and transmittance of polarizers are between 20 dB and 33 dB, and 13 dB and 27 dB for 10 µm and 20 µm pitch wire-grids, respectively, and 100% at central frequency, depending on frequency and AR layer thickness. The process of polarizer fabrication is simple from mature semiconductor manufacturing techniques that lead to high yield, low cost, and potential for THz applications.