Infrared Wire-Grid Polarizer with Antireflection Structure by Imprinting on Both Sides

Abstract

We fabricated infrared wire-grid polarizers with an antireflection (AR) grating structure by the simultaneous imprinting on both sides of a low-toxicity chalcogenide glass (Sb–Ge–Sn–S system). Silicon carbide and glassy carbon plates were used as molds for the direct glass imprinting. A wire-grid polarizer of 100-nm-thick was produced by depositing Al obliquely on the grating. Although the transmittance of the chalcogenide glass substrate was 62–66% in the 8.5–10.5 µm wavelength range, the transverse magnetic (TM) transmittance of the fabricated element became higher than 70% owing to the AR structure. The extinction ratio was larger than 20 dB at 11 µm wavelength.

Nanogap Engineering for Enhanced Transmission of Wire Grid Polarizers in Mid-Wavelength Infrared Region

“…It shows that the overall transmittance for the TM polarization in the MWIR wavelength regime of more than 85% increases with a decrease in the air gap between the Al nanowires, with the peak transmittance achieved with an air gap of 6 nm. We note that a surface reflection of ~30% that occurs at the bottom side of the Si substrate is not considered, because this can be improved using the previously reported AR approaches 5 – 7 . Figure S1 in the Supplementary Information (SI) presents one exemplary AR coating comprising 6 dielectric layers, which can highly suppress the reflections over the MWIR range of 3000–5000 nm, and the transmission spectra of a bare Si substrate with and without the designed AR coating.…”

“…However, it is difficult to achieve broadband characteristics with a single AR layer. Although microstructures directly patterned at the subwavelength scale on a chalcogenide glass via an imprinting process have been demonstrated to mitigate the reflection losses, the PER was found to be less than 20 dB due to a reduction of the TM transmission at the short wavelength regime arising from the diffraction and a high leakage loss of the TE transmission resulting from the misalignment of the direction of the imprinted chalcogenide glass grating with that of the metal wire grating 7 . Besides, handling the WGP device with the microstructure-based AR surfaces is difficult.…”

Fabrication of Silicone Grating Using a Photoimprinted Polymer Mold and Period Control by Mechanical Distortion

“…The process is composed of three main steps: preparation of the master mold with a SiC substrate, photoimprinting of polymer using the SiC mold, and molding of silicone solution using the fabricated polymer mold. A SiC substrate of 25 × 25 × 2 mm 3 size (Ad-map Corp.) was used for the mold because of its hardness [7,8]. The photoresist was coated onto the SiC substrate coated onto a WSi film using sputtering method and was exposed by drawing of He-Cd laser (442 nm wavelength) beams for generation of the 3 μm pitch grating structure.…”

“…The WSi mask layer and the SiC substrate were etched, respectively, using SF 6 and CHF 3 gases. The etching conditions were adjusted to fabricate the tapered grating considering the secure demolding [7,8]. Figure 2 presents scanning electron microscope (SEM) photographs of the fabricated SiC mold.…”

Dielectric-based Components and Methods for Terahertz Sensing

“…On the other hand, Aluminium based inks are more affordable, but they provide lower performance than Silver based ones [66], because of their higher resistivity ( = [112], NPs printed with a Dimatix DMP -2831 printer [99], films [89] and wires [88]. With lower cost, Aluminium (Al) has been proposed as an affordable metal for thin metal-film subwavelength-grating polarizers for application from UV/visible [94], [87], [113], [114] to the far IR and THz frequencies [97], [115], [100], [95], [101], [93] thanks to its low resistivity [90] compared with tungsten or chromium in this band, the availability of mature deposition techniques for its manipulation (it has a low melting point that is insensitive to evaporator conditions [92]) and it is cheaper than gold or silver. However, both Aluminium and Silver have been tested with coatings.…”