Terahertz amplification and lasing by using transverse electric modes in a two-layer-graphene-dielectric waveguide...

Area of Science:

• Condensed Matter Physics
• Optics and Photonics
• Materials Science

Background:

• Graphene exhibits unique electronic properties at terahertz (THz) frequencies.
• Waveguide modes in graphene structures are crucial for THz wave manipulation.
• Efficient coupling between free-space THz waves and guided modes is challenging.

Purpose of the Study:

• To investigate the interaction between freely propagating THz waves and graphene waveguide modes.
• To explore the phenomenon of resonance between THz waves and surface transverse electric (TE) modes.
• To demonstrate THz amplification and lasing using a two-layer graphene structure.

Main Methods:

• Theoretical investigation of surface TE modes in a dielectric waveguide with two DC-biased graphene layers.
• Analysis of graphene's complex conductivity at THz frequencies.
• Study of dispersion, amplification, and lasing conditions for TE modes.

Main Results:

• Discovered resonance between incident THz waves and graphene waveguide surface TE modes near the light cone.
• Demonstrated amplification and lasing of THz waves via TE mode excitation.
• Showed that DC bias creates necessary capacitive complex conductivity for TE modes.
• Identified that negative real part of graphene conductivity leads to THz amplification and lasing.
• Two-layer graphene reduces the required charge-carrier drift velocity for lasing.

Conclusions:

• Freely incident THz waves can directly resonate with graphene waveguide TE modes.
• The proposed two-layer graphene structure enables efficient THz amplification and lasing without external coupling elements.
• This approach offers a promising pathway for developing novel THz devices and sources.