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Increasing efficiency of high numerical aperture metasurfaces using the grating averaging technique.
Amir Arbabi1, Ehsan Arbabi2, Mahdad Mansouree3
1Department of Electrical and Computer Engineering, University of Massachusetts Amherst, 151 Holdsworth Way, Amherst, MA, 01003, USA. arbabi@umass.edu.
Scientific Reports
|April 30, 2020
Summary
Researchers developed a new technique to estimate the efficiency of high numerical aperture (NA) optical metasurfaces. This method enables the design of larger, more efficient metasurfaces, demonstrated by a metalens with 0.78 NA and 77% focusing efficiency.
Area of Science:
- Optics and Photonics
- Metamaterials
- Nanophotonics
Background:
- Optical metasurfaces offer advantages over conventional diffractive optical elements for efficient light deflection.
- Current metasurface design methods are optimized for small deflection angles, limiting performance for high numerical aperture (NA) devices.
- The efficiency of metasurfaces for high NA applications is not well quantified.
Purpose of the Study:
- To introduce and apply a novel technique for estimating the efficiency of high NA metasurfaces.
- To enable the design of arbitrarily large metasurfaces, overcoming limitations of simulation-based methods.
- To identify unconventional metasurface designs for high NA applications.
Main Methods:
- A technique based on coherent averaging of diffraction coefficients of periodic blazed gratings.
- Comparison of different metasurface designs for high NA device implementation.
- Experimental demonstration of a metalens using the developed technique.
Main Results:
- An unconventional metasurface design was identified.
- A metalens with a numerical aperture (NA) of 0.78 was experimentally demonstrated.
- A measured focusing efficiency of 77% was achieved for the metalens.
Conclusions:
- The gradient averaging technique is a versatile tool for designing efficient metasurface components and systems.
- This method allows for the design of arbitrarily large metasurfaces, unlike optimization-based methods.
- The developed technique enables highly efficient metasurface-based optical devices.
