Broadband high-performance terahertz polarizers by nanoimprint lithography for advanced applications

Terahertz polarizers are needed for advanced spectroscopic systems, but they have drawbacks such as low transmission, short bandwidths, and low extinction ratios. A method for the development of ultrabroadband THz polarizers based on the nanoimprint lithography technique is reported here, in which high performance is achieved for a double-wire-grid polarizer (DWGP) structures on cyclic olefin copolymer (COC) substrates. Over the 0.1-25 THz frequency range, the polymer DWGPs exhibited more than twice the TM-polarized transmittance of their silicon-based counterparts. The degree of polarization was greater than 98% in the 0.1-16 THz range, and the extinction ratio was greater than 65.4 dB at 4.2 THz. THz time-domain spectroscopy (THz-TDS) and Fourier-transform infrared spectroscopy (FTIR) were also employed to characterize the optical properties of materials over the frequency ranges of 0.1-40 THz and 0.9-20 THz, respectively. The nanofabricated polymer DWGP showed better optical properties than the Si DWGP in terms of enhanced TM transmittance and reduced TE leakage. In addition, the prepared COC polarizers exhibited cost-effectiveness, scalability, and durability and can be considered environmentally friendly alternatives to conventional Si-based polarizers. This study opens up the possibility of using polymer-based DWGPs as important high-performance components in THz imaging and sensing applications and in wireless communication systems.