Highly Tunable Cascaded Metasurfaces for Continuous Two-Dimensional Beam Steering

Area of Science:

• Optics and Photonics
• Metasurface Technology

Background:

• Cascaded metasurfaces offer dynamic light manipulation through mechanical tuning.
• Current designs require sub-wavelength gaps, hindering practical implementation and far-field operation.

Purpose of the Study:

• To propose a novel design paradigm for cascaded metasurfaces overcoming gap size limitations.
• To demonstrate a practical, tunable two-dimensional (2D) beam-steering device.

Main Methods:

• Utilized a ray-tracing scheme for optimal metasurface operation at achievable gap sizes.
• Designed a 2D beam-steering device based on the lateral translation of two cascaded metasurfaces.
• Validated the design through simulations and experimental measurements at 1064 nm.

Main Results:

• Achieved biaxial deflection angles of ±45° with ±3.5 mm lateral translations.
• Maintained low light divergence (<0.007°).
• Experimental results closely matched theoretical predictions with uniform optical efficiency.

Conclusions:

• The proposed generalized design paradigm enables tunable cascaded metasurface devices.
• This approach overcomes practical implementation challenges associated with small gap sizes.
• The technology holds promise for applications in LiDAR and free-space optical communication.