Metasurface optic for Gaussian beams accepts a nonplanar input beam

Aug. 1, 2019
Most metasurface optics only accept plane-wave beams; a new hybrid metal-dielectric metastructure focuses a diverging Gaussian beam back on itself.

With their potential ability to replace bulk-glass optical components, and even entire optical systems, metasurface optics have come a long way in their capabilities, including high-numerical-aperture (NA) operation and multispectral or broadband operation. But most metasurface optics today are designed to accept and modify plane waves, eliminating the possibility of finite-conjugate metasurface optics. Researchers at the Chalmers University of Technology (Göteborg, Sweden) and Politecnico di Torino (Turin, Italy) have now theoretically developed a metasurface, designed for use with monochromatic Gaussian beams, that reflects a diverging beam and forms a converging beam in the process (in other words, it’s the metasurface analogue of a concave spherical mirror)—the process has an efficiency of higher than 90%.

In the model, the subwavelength metasurface elements (meta-atoms) are fins of titanium dioxide (TiO2) with varying orientations (producing differing phases) in almost-periodic arrays. Both all-dielectric and hybrid metal-dielectric structures were modeled for wavelengths in the near-infrared, with most of the modeling done on the hybrid metal-dielectric version. The array period was 380 nm—the difference in phase between consecutive elements grew quadratically with the distance from the optical axis. The whole reflective metasurface had a radius of 12.57 µm and a focal length of 50 λ. The beam waist was 3.21 µm for both the incoming and reflected beams, with a close-to-ideal beam profile. An example phase profile for the ideal Gaussian field (blue line in figure) and cross-polarized reflected field (red dotted line) at a distance of 1350 nm from the surface matched well for the hybrid metal-dielectric structure. Reference: J. Martínez-Llinàs et al., Opt. Express, 27, 15 (Jul. 22, 2019); https://doi.org/10.1364/oe.27.021069.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Sponsored Recommendations

Achromatic Lenses: High-Quality Custom Optics

March 13, 2025
Ensure clarity and accuracy in your optics systems with Lacroix’s achromatic lenses. Explore how our custom solutions minimize chromatic aberration for perfect results.

Manufacturing Considerations for Tolerancing Aspheres

March 13, 2025
Understand the critical factors in manufacturing aspheres and how Lacroix Optics ensures precise tolerancing in every optical component.

Explore Our Videos: Insights into Precision Optics

March 13, 2025
Get an inside look at Lacroix Optics with our collection of informative videos showcasing our capabilities, innovations, and processes.

Optical Assemblies: Reliable and Precise Solutions

March 13, 2025
Ensure your optical system works seamlessly with Lacroix Optics' custom optical assemblies. Discover the precision and reliability we bring to every project.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!