Optically Controlled Nano-Transducers Based on Cleaved Superlattices for Monitoring Gigahertz Surface Acoustic...

Area of Science:

• Acoustics
• Materials Science
• Nanotechnology

Background:

• Surface acoustic waves (SAWs) are crucial for various applications, including sensing and signal processing.
• Current opto-acousto-optic transducers (OAOTs) are limited to below 100 GHz due to fabrication and electronic constraints.
• Existing methods struggle to achieve higher frequencies for coherent SAWs.

Purpose of the Study:

• To introduce cleaved superlattices (SLs) as unconventional, optically controlled nanotransducers for generating high-frequency SAWs.
• To demonstrate the feasibility of using SLs for generating and detecting acoustic waves at GHz frequencies.
• To explore the potential of SLs for future sub-THz to THz nanoacoustic applications.

Main Methods:

• Utilized ultrafast lasers in a pump-probe configuration on cleaved superlattices (SLs).
• Employed SLs composed of alternating AlGa_1-As and AlGa_1-As layers with ~70 nm periodicity.
• Investigated acoustic vibrations generated and detected by laser beams incident on the nanostructured surface.

Main Results:

• Successfully generated and detected acoustic vibrations in the 40-70 GHz range.
• Observed generalized surface Rayleigh mode and bulk modes within the dispersion relation.
• Demonstrated the potential for surface-skimming longitudinal and transverse acoustic waves at GHz frequencies.

Conclusions:

• Cleaved superlattices offer a promising alternative to conventional transducers for high-frequency nanoacoustics.
• This proof-of-concept opens avenues for generating sub-THz to THz coherent surface acoustic vibrations.
• The atomic-scale precision in SL growth enables future advancements in terahertz acoustics.