Reflectionless graphene perfect absorber based on parity symmetric unidirectional guided resonance

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Graphene perfect absorbers (GPAs) are crucial for optical devices.
• Achieving high absorption while maintaining transmission is challenging.
• Existing designs often suffer from reflection losses.

Purpose of the Study:

• To propose a reflectionless graphene perfect absorber (GPA).
• To demonstrate high absorption with an open transmission channel.
• To develop an efficient transmissive optical modulator based on the GPA design.

Main Methods:

• Numerical demonstration of a GPA using monolayer graphene on a silicon photonic crystal slab.
• Utilizing parity symmetric unidirectional guided resonances (UGRs).
• Modulating absorption by varying graphene's Fermi energy level.

Main Results:

• Achieved peak absorption of 99.97% in the near-infrared.
• Demonstrated a transmissive optical modulator with 28 dB modulation depth and 0.31 dB insertion loss.
• Showcased the tunability of the device by adjusting Fermi energy.

Conclusions:

• The proposed reflectionless GPA design enables forbidden reflection and open transmission.
• The GPA serves as a foundation for efficient transmissive optical modulators.
• The design strategy is adaptable to other two-dimensional (2D) materials for optical applications.