Extremely high extinction ratio terahertz broadband polarizer using bilayer subwavelength metal wire-grid structure

We report a broadband terahertz (THz) polarizer exhibiting extremely high polarization extinction ratio and the method to fabricate it. The polarizer consists of a bilayer subwavelength Au wire-grid structure fabricated on Si substrate by one step etching and metal formation. The THz time domain spectroscopy (THz-TDS) measurement reveals an extremely high extinction ratio of 84.9 dB at 1.67 THz, close to the detection limit of THz-TDS system, and an average extinction ratio of 69.9 dB in 0.6–3 THz frequency range. The fabricated bilayer wire-grid polarizer shows greatly enhanced performance over conventional single layer wire-grid THz polarizer.