Achromatic Metalens With Polarization Insensitivity

Lenses work with various wavelengths and applications, including phone cameras, microscopes, and sensors. They must, first and foremost, be able to focus light regardless of its polarization. Researchers have long believed symmetric nanostructures, such as circular pillars, are critical components in developing polarization-insensitive photonic devices. Researchers have created polarization-insensitive metalens made of non-symmetric nanofins that can achromatically focus light across the visible spectrum without aberrations.

A flat lens of this type is helpful for various applications, including virtual or augmented reality headsets, microscopy, lithography, sensors, and displays.

They have doubled the efficiency of the metalens from previous iterations by making this lens polarization-insensitive. It is the first paper to show achromatic and polarization insensitive focusing in the visible spectrum. Previous research showed that arrays of titanium dioxide nanofins could equally focus light wavelengths and eliminate chromatic aberration, but those lenses could only focus circularly polarized light.

It meant they were effectively discarding half of the incident light that did not have the correct polarization. The researchers changed the layout of the nanofins in this latest design, positioning each pillar so that it is either parallel or perpendicular to its neighbor. This new design allows for more freedom in tuning the geometrical parameters of the metalens, allowing for better achromatic focusing across the entire visible range.

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