Tailoring exceptional points with one-dimensional graphene-embedded photonic crystals.

Area of Science:

• Photonics
• Materials Science
• Condensed Matter Physics

Background:

• Exceptional points (EPs) are unique degeneracies in non-Hermitian systems with potential applications in sensing and optical devices.
• Graphene's tunable electronic properties offer a promising route for dynamic control of optical phenomena.
• One-dimensional (1D) photonic crystals provide a versatile platform for manipulating light propagation.

Purpose of the Study:

• To theoretically demonstrate the realization of tunable exceptional points (EPs) in graphene-embedded 1D photonic crystals.
• To investigate the influence of graphene's Fermi level on the emergence and tunability of EPs.
• To explore the topological characteristics of these EPs and their potential for optical device applications.

Main Methods:

• Theoretical modeling of 1D photonic crystals incorporating a graphene sheet.
• Analysis of band structures and optical properties under varying Fermi levels.
• Investigation of eigenvalue spectra to identify and characterize EPs and their topological features.

Main Results:

• Tunable EPs were theoretically demonstrated in graphene-embedded 1D photonic crystals operating in the terahertz (THz) frequency range.
• Significant alteration of energy bands and the appearance of EPs were achieved by tuning the graphene Fermi level.
• Multiple EPs at distinct frequencies were selectively produced by adjusting the photonic crystal's band structure.
• Topological features of EPs, including eigenvalue crossing and anti-crossing, were analyzed.

Conclusions:

• Tunable EPs can be effectively realized in graphene-based 1D photonic crystals.
• Optical pumping of graphene offers a method for dynamic control of EPs in the THz range.
• These findings provide a pathway for designing active optical devices utilizing photoexcited graphene.