Two-photon 3D printing diaphragm-integrated ring waveguide coupler for ultrasound detection

Area of Science:

• Photonics and Sensing Technologies
• Optical Fiber Sensors
• Acoustic Wave Detection

Background:

• Optical fiber sensors offer advantages like immunity to electromagnetic interference and remote sensing capabilities.
• Ultrasonic sensing requires high sensitivity and low noise for accurate acoustic wave detection.
• Integrating micro-optical components with optical fibers is crucial for advanced sensor development.

Purpose of the Study:

• To demonstrate a novel diaphragm-integrated ring waveguide coupler as an ultrasonic sensor.
• To investigate the sensor's performance in terms of sensitivity and noise equivalent acoustic signal level.
• To explore the potential of this device in various acoustic wave sensing applications.

Main Methods:

• Fabrication of the sensor using the two-photon direct laser writing technique.
• Integration of a micro-ring waveguide (5 µm diameter) as a light reflection mirror on an optical fiber tip.
• Coupling a diaphragm to a straight waveguide to enable ultrasound-induced variation in the coupling gap.

Main Results:

• The device functions as an ultrasonic sensor by modulating light reflection through ultrasound-induced changes in the coupling gap.
• Achieved a high sensitivity and a low noise equivalent acoustic signal level of 1.07 mPa/Hz^1/2 at 100 kHz.
• Demonstrated that diaphragm size optimization can tune the vibration frequency based on plate vibration theory.

Conclusions:

• The diaphragm-integrated ring waveguide coupler is a viable and effective ultrasonic sensor.
• The sensor exhibits excellent performance characteristics, making it suitable for demanding acoustic sensing tasks.
• This technology holds significant promise for advancing acoustic wave sensing applications.