A fractional phase-coding strategy for terahertz beam patterning on digital metasurfaces.

Area of Science:

• Metasurfaces and Wavefront Engineering
• Terahertz (THz) Technology
• Electromagnetics and Optics

Background:

• Metasurfaces offer digital wave manipulation at subwavelength scales, but current coding strategies lack flexibility for advanced applications.
• Existing phase gradient metasurfaces and phase coding techniques are limited in field of view and targeting accuracy.
• There is a growing demand for sophisticated and flexible coding strategies for terahertz wavefront manipulation.

Purpose of the Study:

• To present a generalized coding method for precise terahertz wavefront manipulation.
• To overcome the limitations of rigidity in phase gradient division for expanded applications.
• To enable anomalous scattering and ultrafine radiation patterning with enhanced flexibility.

Main Methods:

• Developed a generalized coding method by reconfiguring the array factor using phased array theory and metasurface concepts.
• Introduced a fractional coding method by discretizing supercell spacing for arbitrary phase gradient distribution.
• Fabricated and measured 2-bit coding metasurfaces with four fractional coding sequences.

Main Results:

• Demonstrated consecutive single-beam steering from 22° to 74° across 0.34-0.5 THz using fractional phase-coding metasurfaces.
• Achieved single to multiple beam scanning in an expanded angular range with minimal steps by switching coding sequences or frequencies.
• Validated results through numerical prediction, simulation, and experimental measurements, showing good accordance.

Conclusions:

• The proposed fractional coding strategy enables delicate beam regulation for high-resolution imaging and detection.
• This method offers enhanced flexibility and precision in terahertz wavefront manipulation compared to conventional techniques.
• The findings pave the way for advanced applications in terahertz optics and electromagnetics.