An acousto-optic sensor based on resonance grating waveguide structure

• We demonstrate an acousto-optic ultrasound sensor.
• The sensor is based on resonance waveguide grating structure.
• Elastic polymers are used for a potential improvement of acousto-optic sensitivity.
• Planar sensor structure is suitable for two-dimensional ultrasound imaging.
• 20 MHz ultrasound signal is successfully measured using a fabricated sensor.

This paper presents an acousto-optic (AO) sensor based on resonance grating waveguide structure. The sensor is fabricated using elastic polymer materials to achieve a good sensitivity to ultrasound pressure waves. Ultrasound pressure waves modify the structural parameters of the sensor and result in the optical resonance shift of the sensor. This converts into a light intensity modulation. A commercial ultrasound transducer at 20 MHz is used to characterize a fabricated sensor and detection sensitivity at different optical source wavelength within a resonance spectrum is investigated. Practical use of the sensor at a fixed optical source wavelength is presented. Ultimately, the geometry of the planar sensor structure is suitable for two-dimensional, optical pressure imaging applications such as pressure wave detection and mapping, and ultrasound imaging.