A Thermally Stable, Infrared-Transparent High-Sulfur-Containing Polymer for High Aspect-Ratio Nanostructured MWIR...

Infrared (IR) polarizer is essential for thermal imaging applications such as mobility and military operations. High-sulfur-containing polymers have emerged as promising candidates for IR polarizers due to their mid-wave IR (MWIR) transparency, addressing the limitations of inorganic materials, including their brittleness and high cost. However, poor thermal stability and limited IR range restrict their applicability. This study introduces a glassy IR polarizer based on poly(sulfur-co-hexavinyl disiloxane) (pSHVDS), a highly crosslinked sulfur-rich polymer synthesized via sulfur chemical vapor deposition (sCVD). Self-crosslinking of pSHVDS at high temperatures provided thermal stability during nanoimprint lithography, enabling the fabrication of high-fidelity nano-grating patterns (400 nm pitch, 150 nm width, 300 nm height). The broad transmittance and high aspect ratio of the nanopattern enabled the glassy-pSHVDS MWIR polarizer to achieve over 50% transmittance of transverse magnetic field (T_TM) and an extinction ratio (ER) exceeding 6000 across a broad IR range (3-8 µm). An additional pSHVDS anti-reflection coating further enhanced T_TM to 84% and ER to 7200 at a wavelength of 4 µm, the highest ER reported for organic MWIR polarizers to date. The polarizer maintained its performance after 24 h at 100 °C, demonstrating exceptional thermal stability. These findings underscore the potential of glassy pSHVDS-based polarizers for IR applications.