Metasurface with multi-sized structure for multi-band coherent perfect absorption.

Area of Science:

• Metamaterials and Nanophotonics
• Optical Engineering
• Condensed Matter Physics

Background:

• Coherent perfect absorption (CPA) enables near-total light absorption at specific frequencies.
• Metasurfaces offer tunable optical properties through subwavelength structuring.
• Achieving broadband and tunable CPA is crucial for advanced optical applications.

Purpose of the Study:

• To demonstrate multi-band coherent perfect absorption (CPA) using a novel metasurface design.
• To investigate the tunability and polarization independence of the CPA.
• To explore the potential of the optimized metasurface as an optical device.

Main Methods:

• Fabrication of a metasurface unit cell comprising columnar metal patches and a dielectric layer.
• Experimental and theoretical analysis of light absorption under coherent illumination.
• Systematic variation of structural parameters (patch radius, dielectric thickness) to optimize CPA.
• Investigation of absorption spectra for different polarizations and incidence angles.

Main Results:

• Achieved multi-band CPA at infrared frequencies with enhanced absorption bandwidth (3x compared to single-band).
• Demonstrated polarization-independent CPA, tunable at each resonant frequency via phase control of incident beams.
• Showcased resonant frequency sensitivity to columnar patch radius, enabling a wide CPA frequency range.
• Obtained near-perfect absorption at oblique incidence for both TE and TM polarizations.

Conclusions:

• The designed metasurface effectively achieves broadband, tunable, and polarization-independent multi-band CPA.
• The metasurface's resonant properties can be precisely controlled by structural parameters.
• The optimized metasurface shows promise for applications such as efficient optical filters and beam splitters.