Nonreciprocal reflection based on asymmetric graphene metasurfaces

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Nonreciprocal optical devices are crucial for integrated photonics.
• Achieving efficient and tunable nonreciprocity, especially in reflection mode, remains a challenge.

Purpose of the Study:

• To propose and demonstrate a novel asymmetric graphene metasurface for controllable nonreciprocal behavior.
• To investigate the underlying mechanisms of asymmetric reflection in the near-infrared range.

Main Methods:

• Fabrication of asymmetric metasurfaces using a continuous graphene sheet and a polycrystalline silicon slab with periodic grooves.
• Characterization of optical properties, focusing on reflection asymmetry and nonreciprocal reflection ratio.
• Analysis of nonlinear effects contributing to nonreciprocity.

Main Results:

• Demonstrated completely asymmetric reflection in opposite directions in the near-infrared range.
• Achieved a high nonreciprocal reflection ratio of 21.27 dB with minimal insertion loss of -0.76 dB.
• Showcased dynamic tunability by controlling incident field intensity and graphene Fermi level.

Conclusions:

• The proposed graphene metasurface design offers a promising route towards miniaturized, integratable nonreciprocal optical components.
• This work facilitates advancements in integrated isolators, optical logic circuits, and bias-free nonreciprocal photonics.