Nonlocal Metasurface Lens for Long-Wavelength Infrared Radiation

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Dielectric metasurfaces offer enhanced optical functionalities in ultrathin devices.
• Scaling visible/near-infrared metasurface designs to long-wave infrared (LWIR) is challenging due to thickness and material absorption.
• Nonlocal metasurfaces offer a promising platform for LWIR applications by utilizing extended resonances.

Purpose of the Study:

• To demonstrate nonlocal metalenses operating in the LWIR spectrum.
• To address the limitations of conventional metasurfaces in the thermal infrared region.
• To introduce a novel meta-unit design for enhanced metasurface performance.

Main Methods:

• Fabrication of nonlocal metalenses using germanium thin films on a zinc-selenide substrate.
• Operation at a wavelength of approximately 10.3µm with a device thickness of 1.45µm (14% of the free-space wavelength).
• Design of a novel square lattice meta-unit with isotropic dispersion features.

Main Results:

• Demonstration of ultrathin nonlocal metalenses operating effectively in the LWIR.
• Achieved a deeply subwavelength device thickness, overcoming conventional limitations.
• Showcased a meta-unit geometry with frequency-stable resonant geometric phase.

Conclusions:

• The developed nonlocal metalenses are suitable for multi-functional, low-profile meta-optics in the challenging thermal spectral region.
• The novel meta-unit design simplifies the rational design of complex metasurface operations.
• This platform holds promise for advanced imaging and sensing applications in the LWIR spectrum.