Bidirectional invisibility in Kramers-Kronig optical media

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Invisibility cloaking has been a long-standing goal in optics.
• Kramers-Kronig media, a recent discovery, possess unique electromagnetic properties.
• Controlling light interaction with materials is crucial for advanced optical devices.

Purpose of the Study:

• To introduce a broad class of planar dielectric media exhibiting full invisibility.
• To explore the properties of these media, specifically their relation to Kramers-Kronig relations.
• To investigate the transition from unidirectional to bidirectional invisibility and sharp reflection phenomena.

Main Methods:

• Theoretical introduction of planar dielectric media with complex permittivity profiles.
• Analysis based on Kramers-Kronig relations, linking real and imaginary parts of permittivity via Hilbert transform.
• Investigation of electromagnetic wave propagation and reflection characteristics.

Main Results:

• A class of locally isotropic, non-magnetic dielectric media exhibiting bidirectional invisibility is defined.
• The spatial profiles of permittivity are shown to be related by a Hilbert transform, consistent with Kramers-Kronig relations.
• Conditions for transition to bidirectional invisibility and sharp reflection above a cut-off angle are discussed.

Conclusions:

• The study presents a novel class of materials enabling full optical invisibility.
• These Kramers-Kronig media offer tunable control over light reflection and transmission.
• The findings open new avenues for designing advanced optical cloaking and manipulation devices.