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3d Printed Multilayer Structures for Achromatic Lenses With Large Numerical Apertures

Bylima

Dec 30, 2023
3d Printed Multilayer Structures for Achromatic Lenses With Large Numerical Apertures

High-refractive index materials are incorporated into nanostructures to create lenses with thin form factors that are only functional at particular wavelengths, which is how flat optics are made.

Recently, efforts have been made by materials scientists to create achromatic lenses to determine the trade-off between bandwidth and numerical aperture that restricts the capabilities of these materials. In this work, Cheng-Feng Pan and a group of scientists from China and Singapore with backgrounds in computer engineering, information technology, and engineering product development proposed a novel method for creating multilayer achromatic metalenses with high numerical aperture, broadband, and insensitivity to polarization.

The materials scientists used two-photon lithography to inversely design the metalenses by combining topology optimization with full wavelength simulations. The research team used red, green, and blue narrowband illuminations along with white light to demonstrate the engineered structures’ broadband imaging capabilities.

The results demonstrated how 3D-printed multilayer structures could be used to create broadband and multipurpose metadevices. The results have been published in Science Advances and are showcased on the journal’s cover page.

Visual Performance

Recent advancements in both macro and micro-scale metalenses have demonstrated the importance of achieving exceptional imaging performance appropriate for a range of applications in quantum technologies, bioanalysis, light-field imaging, and medicine. For example, broadband responses are displayed by achromatic lenses to capture color information, thereby increasing the design options and application scenarios for photonic devices.

These structures are incredibly lightweight, thin, and compact, making them ideal for creating powerful metal lenses for imaging systems. Broadband implementation is difficult because most metalenses are patterned in high refractive index materials, which offer good optical control but have a strong light.

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In lens design, physicists have demonstrated the Abbe number’s value as a formula to achieve a high-efficiency focusing lens and as a figure of merit to represent a dispersion-free transparent material that is frequently used for high-refractive index materials.

The Process of 3D Printing

By using three-dimensional printing, the research team was able to overcome the fabrication challenges that underlie multilayer achromatic metalenses. Complex structures could be quickly prototyped by patterning a multilayer lens in a single lithographic step thanks to the nanoscale 3D printing technique. The researchers created a range of 3D designs, such as diffractive lenses, gradient index lenses, and intricate microlenses, using two-photon polymerization.

In this work, achromatic lensing behavior was achieved through topology optimization by Pan and colleagues. They swiftly produced a multilayer, stable, and highly resolved structure.

The resultant multilayer achromatic metalenses demonstrated previously unheard-of levels of effective performance, combining the benefits of high-resolution 3D printing at the nanoscale to produce metalenses with remarkable performance that will spur the development of novel approaches to the design and manufacture of multifunctional broadband optical elements and devices.

Creating Multilayer Achromatic Metal Lenses and the Results of the Experiments

The size of the smallest feature is the main distinction between multilevel diffractive lenses and multilevel metals.

For example, the minimum feature size can be tailored to fit a particular dimension, but full-wave simulations are needed to take scattering and interlayer interactions into consideration. The scientists created a real construct out of the designed structure by applying filtering and binarization steps.

The samples were formed using the Nanoscale GmbH photonic professional 3D printing system, with a galvo-scanned focused beam used to induce crosslinking of a liquid resin into a nanoscale solid voxel at the focal spot. The samples were then subjected to topology optimization.

The scientists placed the product on a resolution target that was three times the focal length away from the objectives to evaluate the imaging quality. They then optimized the fabrication process to produce a prototype that was nearly identical to the original design.

The engineered metalens demonstrated their unparalleled ability to eliminate chromatic aberrations by performing well under white light for achromatic imaging applications. The multilayer achromatic metalenses demonstrated high focusing efficiency with broadband performance and topological optimization to precisely realize the designed metalenses with nanoscale features, as demonstrated by the scientists’ optimization of the parameters.

Prospects

Cheng-Feng Pan and the research group created a multilayer metalens system in this manner, treating each layer as a focusing element and achromatic corrector. The outcomes demonstrated how the low-refractive index materials-based stacked metasurfaces overcome the limitations of single-layer flat optics to enable the metalenses to perform broadband functions while maintaining a high numerical aperture.

High refractive index resins and higher resolution 3D printing techniques will help create a more multifunctional optical system that can operate in the near or mid-infrared spectrum and has a broadband response range that extends beyond the visible spectrum.

By lima

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