Enhanced Photon-Phonon Interaction in WSe₂ Acoustic Nanocavities

Area of Science:

• Solid State Physics
• Materials Science
• Nanotechnology

Background:

• Acoustic nanocavities (ANCs) operating above 1 GHz are crucial for advanced sensors and quantum devices.
• Van der Waals (vdW) nanolayers enable ANCs with resonance frequencies up to 1 THz and quality factors of 10^3.
• Optical methods are essential for generating and detecting coherent phonons at these high frequencies, as electrical methods are insufficient.

Purpose of the Study:

• To experimentally and theoretically investigate acoustic nanocavities fabricated from WSe2 layers.
• To study the amplitude of optically measured acoustic signals from the breathing mode in ANCs.
• To explore the potential of ANCs with exciton resonance for high-frequency phonon operations at elevated temperatures.

Main Methods:

• Fabrication of ANCs using WSe2 layers (8-130 nm thick) on silica colloidal crystals.
• Optical probing of the acoustic signal using a single wavelength near the exciton resonance.
• Measurement of relative reflectivity changes induced by coherent phonons up to 3 × 10^-4 for frequencies around 100 GHz.

Main Results:

• Demonstrated enhancement of photon-phonon interaction across a broad range of acoustic frequencies.
• Observed high sensitivity of the acoustic signal amplitude to photoelastic constants near the exciton resonance.
• Discovered a photoelastic resonance in nanolayers with thickness near the Bragg condition.

Conclusions:

• WSe2-based ANCs show significant potential for acousto-optical devices.
• The study reveals key mechanisms governing photon-phonon interaction in these nanostructures.
• ANCs with exciton resonance are capable of operating with high-frequency single phonons at elevated temperatures.