Resonant SAW-nanofiber acousto-optic coupling for high-sensitivity detection

Area of Science:

• Photonics and Nanotechnology
• Acousto-Optics and Sensing

Background:

• Conventional acousto-optic sensing methods often face limitations in sensitivity and detection bandwidth.
• Spontaneous forward Brillouin scattering can introduce noise and limit performance in interferometric systems.

Purpose of the Study:

• To develop an externally driven intermodal phase modulation technique for enhanced acousto-optic sensing.
• To achieve narrow detection bandwidths approaching the Hz level for high-resolution measurements.

Main Methods:

• Integration of a dual-core As2Se3 nanofiber interferometer within a surface acoustic wave (SAW) cavity.
• Utilizing a thin liquid coupling layer to convert Rayleigh SAW into a leaky SAW, enabling modulation.
• Employing coherent detection with balanced receivers and polarization biasing for common-mode noise rejection.

Main Results:

• Demonstrated externally driven intermodal phase modulation distinct from spontaneous forward Brillouin scattering.
• Achieved modulation sidebands and narrow detection bandwidths approaching the Hz level.
• Minimized the optical noise floor to within ~1 dB of the photodetector dark-noise limit, significantly improving sensitivity.

Conclusions:

• The proposed acousto-optic sensing approach offers a promising platform for high-sensitivity, narrow-bandwidth optical measurements.
• The integration of chalcogenide nanofibers and SAW cavities provides a robust method for advanced sensor development.