Air-gap structure between integrated LiNbO3 optical modulators and micromachined Si substrates

Area of Science:

• Optoelectronics
• Materials Science
• Microsystems Engineering

Background:

• High-speed optoelectronic systems require efficient optical modulators.
• Integrated lithium niobate (LiNbO3) modulators face performance limitations due to silicon (Si) substrate permittivity.
• Substrate effects can reduce the resonant modulation frequency of LiNbO3 modulator chips.

Purpose of the Study:

• To investigate and mitigate the substrate effect on LiNbO3 optical modulators.
• To introduce an air-gap structure to improve modulator performance.
• To demonstrate a fabrication method for the air-gap structure.

Main Methods:

• Utilized low-temperature flip-chip bonding (100 °C).
• Employed silicon micromachining processes.
• Fabricated and experimentally verified an air-gap structure between LiNbO3 modulators and Si substrates.

Main Results:

• The high permittivity of Si substrates was shown to decrease the resonant modulation frequency.
• An air-gap structure effectively prevented the substrate effect.
• Successful fabrication of the air-gap structure was demonstrated.

Conclusions:

• The air-gap structure is a viable solution for overcoming substrate limitations in integrated LiNbO3 optical modulators.
• This approach enables higher resonant modulation frequencies for high-speed optoelectronic applications.
• The demonstrated fabrication method is compatible with existing semiconductor processes.