Light Modulation in Silicon Photonics by PZT Actuated Acoustic Waves

Area of Science:

• Photonics
• Materials Science
• Acousto-optics

Background:

• Tailoring light-sound interactions is key for photonic integrated circuits (PICs).
• Actuating sound in silicon PICs typically needs piezoelectric films like lead zirconate titanate (PZT).
• Existing PZT integration methods on silicon cause optical loss, hindering photonic applications.

Purpose of the Study:

• To integrate high-quality PZT thin films onto silicon-on-insulator (SOI) photonic chips.
• To demonstrate efficient acousto-optic modulation using PZT-actuated acoustic waves in silicon waveguides.
• To achieve figures-of-merit comparable to state-of-the-art modulators without complex fabrication.

Main Methods:

• Grew high-quality PZT thin films on SOI using an optically transparent buffer layer.
• Fabricated interdigital transducers (IDTs) on PZT films using photolithography and electron-beam lithography.
• Generated acoustic waves in MHz and GHz ranges for acousto-optic modulation.

Main Results:

• Demonstrated acousto-optic modulation in silicon waveguides.
• Achieved a VπL of ~3.35 V·cm at 576 MHz with a gold IDT.
• Measured a VπL of ~3.60 V·cm at 2 GHz with an aluminum IDT, considering mass-loading and grating reflection effects.

Conclusions:

• Successfully integrated PZT on SOI photonic chips without optical loss.
• Achieved broadband acousto-optic modulation with figures-of-merit competitive with state-of-the-art SOI modulators.
• The developed method presents a promising route for efficient and integrated acousto-optic devices.