Plasmonic monolithic lithium niobate directional coupler switches

Area of Science:

• Photonics and Optoelectronics
• Materials Science
• Nanotechnology

Background:

• Lithium niobate (LN) is a key material for electro-optic modulators but conventional devices are often too large, costly, and power-intensive.
• The increasing demands of the optoelectronics industry necessitate smaller, more efficient modulation technologies.

Purpose of the Study:

• To demonstrate ultra-compact plasmonic electro-optic directional coupler switches on lithium niobate.
• To enable efficient switching and modulation functionalities with a significantly reduced footprint.

Main Methods:

• Fabrication of nm-thin gold nanostripes on LN substrates to create plasmonic waveguides.
• Guiding coupled electromagnetic modes and electrical signals through closely spaced nanostripes.
• Utilizing the extreme confinement and spatial overlap of slow-plasmon modes and electrostatic fields.

Main Results:

• Achieved 90% modulation depth with 20-μm-long switches.
• Demonstrated broadband electro-optic modulation efficiency of 0.3 V·cm.
• Showcased the potential for μm-scale footprints and ultrafast operation.

Conclusions:

• The developed monolithic LN plasmonic platform enables cost-effective optical communication applications.
• The ultra-compact switches offer high environmental stability and ultrafast operation.
• This technology addresses the limitations of conventional electro-optic modulators for future optoelectronic systems.