Nanoimprinted Tilt-Free Astigmatic Metasurface for One-Shot Orbital Angular Momentum Beam-Array Readout

Area of Science:

• Optics and Photonics
• Metamaterials
• Structured Light

Background:

• Laguerre-Gaussian (LG) beams carry orbital angular momentum (OAM), crucial for optical communications and sensing.
• Converting LG to Hermite-Gaussian (HG)-like patterns simplifies OAM state readout.
• Traditional methods use bulky, tilted optics, limiting practical applications.

Purpose of the Study:

• To demonstrate a compact, tilt-free metasurface for efficient LG-to-HG-like beam conversion.
• To enable intuitive OAM state readout using the generated HG-like patterns.
• To develop a platform for simultaneous spatial and OAM state decoding of beam arrays.

Main Methods:

• Fabrication of a nanoimprinted astigmatic metasurface with a cylindrical nanopillar array.
• Encoding a generalized anisotropic quadratic phase for beam conversion.
• Utilizing normal incidence for LG beam conversion and HG-like pattern generation.

Main Results:

• The metasurface successfully converted LG beams to HG-like patterns at normal incidence.
• OAM state (|l| and sign) was intuitively decoded from the dark-fringe number and orientation.
• Simultaneous spatial mapping and OAM readout of sparse LG beam arrays were achieved in a single frame.

Conclusions:

• The developed metasurface offers a compact, tilt-free solution for LG-to-HG-like conversion.
• This technology enables efficient OAM mode analysis and structured light beam-array decoding.
• The planar and replication-compatible platform advances miniaturized optical systems for OAM applications.