Realization of inversely designed metagrating for highly efficient large angle beam deflection

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Directional emission sources are crucial for multi-view 3D displays.
• Geometric optics struggle with high efficiency and large deflection angles due to weak light confinement.
• Metasurfaces, particularly metagratings, offer advanced light control but face efficiency drops at large angles with conventional design.

Purpose of the Study:

• To develop a novel inverse design method for metagratings enabling high efficiency and large deflection angles.
• To overcome the limitations of forward design methods in controlling Bloch modes for metasurfaces.
• To demonstrate the potential for full-color 3D displays and other functional devices.

Main Methods:

• Utilized an inverse design method to engineer metagrating structures supporting Bloch mode coupling.
• Tailored the total phase response of supercells for specific incident wavelengths (red, green, blue).
• Realized constructive interference among propagation Bloch modes and enhanced outcoupling for desired diffraction orders.

Main Results:

• Achieved theoretical deflection efficiency over 80% for silicon metagratings at 620 nm across a 30°-80° deflection range.
• Experimentally demonstrated a 75° deflection metagrating with 86.43% efficiency, validating the algorithm.
• Projected theoretical efficiencies exceeding 80% for titanium dioxide metagratings at 530 nm and 460 nm.

Conclusions:

• The developed inverse design algorithm reliably produces high-efficiency, large-angle metagratings.
• The method effectively manages Bloch modes and enhances light outcoupling.
• This approach holds significant potential for full-color 3D displays and other advanced photonic devices.