Experimental realization of orbital-angular-momentum-selective coherent perfect absorption

Area of Science:

• Optics and Photonics
• Metamaterials
• Electromagnetics

Background:

• Coherent perfect absorption (CPA) is a phenomenon where incident light is completely absorbed.
• CPA dependent on orbital angular momentum (OAM) has been theoretically proposed but lacked experimental evidence.
• Controlling light absorption based on OAM offers potential for novel photonic devices.

Purpose of the Study:

• To experimentally demonstrate OAM-selective coherent perfect absorption (OAM-CPA).
• To design and validate a device capable of achieving OAM-CPA.
• To explore practical applications in electromagnetic energy harvesting and sensing.

Main Methods:

• Designed an OAM-selective coherent perfect absorber combining a spiral phase plate, polarization-conversion metasurface, and conical cavity.
• Utilized a dual-layer cylindrical absorber with a ceramic core and indium tin oxide (ITO) coating.
• Converted linearly polarized plane waves into cylindrical waves with different OAMs for absorption.

Main Results:

• Successfully validated OAM-selective CPA experimentally.
• Experimental results closely matched numerical simulations.
• Demonstrated CPA for distinct OAM states.

Conclusions:

• The study provides the first experimental validation of OAM-selective CPA.
• The developed device offers a practical method for controlling light absorption based on OAM.
• Findings open avenues for subwavelength electromagnetic energy harvesting and sensing applications.