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

Coherent perfect absorption (CPA) dependent on orbital angular momentum (OAM) has been proposed theoretically but so far has lacked experimental validation. Here, we design an OAM-selective coherent perfect absorber and experimentally validate this intriguing phenomenon. By combining a spiral phase plate, a polarization-conversion metasurface, and a conical cavity, an incident plane wave of linear polarization is converted into cylindrical waves with different OAMs in two dimensions, which impinges on a dual-layer cylindrical absorber composed of a ceramic core and an indium tin oxide (ITO) coating. Experimental results, coinciding well with numerical simulations, confirm the OAM-selective CPA for different OAMs. Our findings offer a practical approach for electromagnetic energy harvesting and sensing at subwavelength dimensions.