Linear polarization-separating metalens at long-wavelength infrared

Area of Science:

• Optics and Photonics
• Materials Science
• Infrared Imaging

Background:

• Long-wavelength infrared (LWIR) imaging is crucial for various applications, but often lacks polarization information.
• Metalenses offer miniaturized and versatile optical solutions, but polarization-selective designs for LWIR are challenging.

Purpose of the Study:

• To design and fabricate a polarization-separation metalens (PSM) using single-crystal silicon (sc-Si) for LWIR imaging.
• To achieve high-performance polarization separation and sensitive imaging in the LWIR spectrum.

Main Methods:

• Fabrication of sc-Si dielectric waveguide pillar meta-atoms with rectangular cross-sections using electron beam lithography and deep reactive ion etching.
• Characterization of the metalens for phase delay range and transmittance for orthogonal polarizations.
• Demonstration of polarization-separation imaging and polarization-sensitive imaging in the LWIR region.

Main Results:

• The PSM demonstrated a full 2π phase delay range for both orthogonal linear polarization components.
• High transmittances (>70%) were achieved for both polarization states.
• High extinction ratios of 21.8 dB (x-polarization) and 12.8 dB (y-polarization) were obtained in polarization-separation imaging.
• Successful demonstration of distinguishing object surfaces based on polarization sensitivity.

Conclusions:

• The developed sc-Si PSM effectively separates and images LWIR light based on polarization.
• This metalens technology enables the visualization of previously invisible information in the LWIR spectrum.
• The PSM has significant potential for widespread applications in LWIR imaging and sensing.