Collimated flat-top beam shaper metasurface doublet based on the complex-amplitude constraint Gerchberg-Saxton...

Area of Science:

• Optics and Photonics
• Metamaterials
• Laser Beam Shaping

Background:

• Collimated flat-top beam shapers are crucial for various applications but face processing and integration challenges, especially at sub-millimeter scales.
• Freeform lenses are commonly used but are difficult to miniaturize.
• Metasurfaces offer a planar alternative, capable of mimicking complex optical functions but conventional designs struggle with amplitude modulation.

Purpose of the Study:

• To propose and demonstrate a novel metasurface doublet design for generating collimated flat-top beams.
• To overcome the amplitude modulation challenges in conventional metasurface designs for beam shaping.
• To achieve high-performance beam shaping comparable to existing freeform lens technologies.

Main Methods:

• Development of a complex-amplitude constraint Gerchberg-Saxton algorithm for metasurface design.
• Simultaneous consideration of meta-atom amplitude and phase characteristics.
• Mitigation of near-field coupling effects on amplitude distribution.

Main Results:

• Experimental realization of a collimated flat-top beam with exceptional homogeneity (U ≈ 0.01).
• Achieved wavefront error below 0.1λ and transmittance exceeding 86%.
• Performance comparable to commercial freeform lens-based beam shapers.

Conclusions:

• The proposed metasurface doublet design effectively generates high-quality collimated flat-top beams.
• The complex-amplitude constraint algorithm successfully addresses amplitude modulation issues in metasurfaces.
• This metasurface approach enables efficient integration with laser systems, particularly for miniaturized optics.