High-Performance All-Optical Terahertz Modulator Based on Graphene/TiO₂/Si Trilayer Heterojunctions

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Terahertz (THz) technology requires efficient modulators for various applications.
• Graphene's unique electronic properties make it a promising material for THz devices.
• Hybrid structures can enhance device performance by combining different material functionalities.

Purpose of the Study:

• To demonstrate a novel trilayer hybrid terahertz modulator.
• To investigate the modulation mechanism based on photoinduced charge transfer.
• To evaluate the performance of the modulator in terms of bandwidth and modulation depth.

Main Methods:

• Fabrication of a trilayer structure consisting of p-type silicon (p-Si), TiO2 interlayer, and single-layer graphene.
• Utilizing the built-in electric field at the Si/TiO2 interface to drive photoelectrons.
• Optical excitation to inject electrons into the graphene layer, altering its Fermi level and conductivity.
• Characterization of terahertz transmission modulation across a broad frequency range.

Main Results:

• Successful demonstration of a graphene/TiO2/p-Si hybrid terahertz modulator.
• Observation of broadband modulation from 0.3 to 1.7 THz.
• Achieved a large modulation depth of 88% under optical excitation.
• Confirmed that photoinduced electron injection into graphene increases conductivity and reduces THz transmission.

Conclusions:

• The developed hybrid nanostructure effectively modulates terahertz transmission.
• The device shows significant potential for broadband terahertz applications.
• This work highlights the promise of hybrid graphene-based materials for future terahertz imaging and communication systems.