Graphene based on-chip variable optical attenuator operating at 855 nm wavelength.

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Optical communication systems require precise control over light signal intensity.
• Graphene's unique electro-optical properties offer potential for novel photonic devices.
• Silicon nitride (Si3N4) waveguides provide a stable platform for integrated photonics.

Purpose of the Study:

• To fabricate and characterize a graphene-based variable optical attenuator (VOA).
• To integrate the VOA onto a silicon nitride photonic waveguide.
• To evaluate the device performance at an 855 nm wavelength.

Main Methods:

• Fabrication of a graphene layer positioned within the evanescent field of a Si3N4 waveguide.
• Application of gate voltage to modulate graphene's optical absorption.
• Characterization of attenuation performance and comparison with theoretical models.

Main Results:

• Achieved a maximum optical attenuation of 17 dB at -3 V gate voltage for a 700 µm device length.
• Experimental results showed good agreement with theoretical simulations based on graphene's optical conductivity.
• Demonstrated the gate voltage-dependent optical absorption of graphene for attenuation.

Conclusions:

• The fabricated graphene-based VOA on Si3N4 waveguides is a viable component for optical signal control.
• The device performance validates theoretical models of graphene's electro-optical behavior.
• Future improvements in layout and fabrication can enhance speed and reduce insertion loss.