Controlling frequency dispersion in electromagnetic invisibility cloaks

Area of Science:

• Physics
• Materials Science
• Electrical Engineering

Background:

• Electromagnetic cloaking is a rapidly developing field, with transformation optics (TO) offering theoretical pathways to invisibility devices.
• Current limitations include extreme material property requirements and narrow operational bandwidths for metamaterial cloaks.

Purpose of the Study:

• To design and simulate a spherical cloak that overcomes the bandwidth limitations of existing metamaterial cloaks.
• To investigate the use of plasma-like metamaterials for achieving broadband electromagnetic cloaking.

Main Methods:

• Designing a spherical cloak incorporating the dispersive nature of permittivity and permeability tensors.
• Simulating the cloak's performance using plasma-like metamaterials.
• Deriving equations of state relating permittivity and permeability tensor eigenvalues.

Main Results:

• The designed spherical cloak demonstrates effective operation over a broad frequency band, despite the highly dispersive nature of the metamaterials used.
• Two key equations of state were established, linking tensor eigenvalues in spherical cloaks irrespective of geometric transformation.
• The study shows that frequency-dispersive properties do not impede cloaking if the derived equations of state are satisfied.

Conclusions:

• Broadband electromagnetic cloaking is achievable using dispersive metamaterials like plasma-like materials.
• The derived equations of state provide a fundamental link between material properties and cloaking performance.
• This work advances the practical realization of metamaterial cloaks with enhanced operational bandwidths.