Unidirectional invisibility in a two-layer non-PT-symmetric slab

Area of Science:

• Optics and Photonics
• Metamaterials
• Electromagnetism

Background:

• Unidirectional invisibility, a phenomenon enabling light to pass through in one direction while being blocked in the other, has been previously achieved using complex parity-time (PT) symmetric periodic structures.
• The fabrication complexity of these PT-symmetric structures presents practical challenges for real-world applications.

Purpose of the Study:

• To propose and numerically demonstrate a simpler, non-parity-time (PT)-symmetric structure for achieving unidirectional invisibility.
• To investigate the tunability of this structure for potential applications in optical switching and cloaking devices.

Main Methods:

• Numerical simulations were employed to analyze a conventional two-layer slab structure.
• The structure's optical properties were investigated by varying the real and imaginary parts of the refractive indices and the thicknesses of the slabs.

Main Results:

• Unidirectional invisibility was successfully achieved in the proposed two-layer non-PT-symmetric slab structure under specific conditions for refractive indices and thicknesses.
• The unidirectional invisibility effect could be controllably converted into unidirectional reflection by adjusting the imaginary parts of the refractive indices to their odd symmetric forms.

Conclusions:

• A simple two-layer non-PT-symmetric slab structure offers a practical alternative for realizing unidirectional invisibility.
• The tunability of the structure's optical response, including conversion to unidirectional reflection, highlights its potential for advanced optical functionalities.