Eliminating Nearfield Coupling in Dense High Quality Factor Phase Gradient Metasurfaces

Area of Science:

• Metasurface optics
• Nanophotonics
• Wavefront engineering

Background:

• High Q factor metasurfaces are crucial for light manipulation.
• Near-field coupling limits the trade-off between quality factor (Q) and resolution.

Purpose of the Study:

• To present a strategy for eliminating coupling-based nonlocal effects in metasurfaces.
• To achieve arbitrarily long resonant lifetimes with sub-diffraction spatial resolution.

Main Methods:

• Utilizing a zero-coupling regime via interference of longitudinal and transverse electric fields.
• Designing metasurfaces composed of meta-pixels with sub-diffraction spatial resolution.

Main Results:

• Demonstrated metasurfaces with Q-factors in the millions and resolution <λ/1.6.
• Achieved >90% diffraction efficiency for beam-splitting (±53°) and beam-steering (33°) with minimal refractive index modulation.
• Experimentally validated the zero-coupling regime via a sign flip in angular dispersion.

Conclusions:

• The zero-coupling strategy removes the Q-factor versus resolution trade-off.
• Fabricated metasurfaces exhibit stable resonant wavelengths over wide incident angles.
• This platform enables precise wavefront shaping with high efficiency, nonlinearity, and programmability.