Low-Cost, High-Performance Fiber Optic Fabry⁻Perot Sensor for Ultrasonic Wave Detection

Area of Science:

• Optoelectronics
• Microelectromechanical Systems (MEMS)
• Acoustics

Background:

• Fiber optic sensors offer advantages in harsh environments.
• Ultrasonic detection is crucial for various industrial and medical applications.
• Existing ultrasonic sensors can be costly or lack sensitivity.

Purpose of the Study:

• To develop a novel, cost-effective extrinsic Fabry–Perot interferometric (EFPI) ultrasonic sensor.
• To leverage Microelectromechanical Systems (MEMS) technology for high-performance diaphragm fabrication.
• To achieve high sensitivity for detecting weak ultrasonic pressure waves.

Main Methods:

• Fabrication of a 5 μm thick silicon diaphragm using MEMS on a silicon-on-insulator (SOI) wafer.
• Integration of the Fabry–Perot (FP) cavity length definition into the diaphragm manufacturing process.
• Utilizing low-cost, commercially available components and MEMS processing.

Main Results:

• The EFPI sensor demonstrated a minimum detectable ultrasonic pressure of 1.5 mPa/sqrt(Hz) between 20 kHz and 40 kHz.
• The sensor design facilitated easier assembly due to integrated cavity length definition.
• The use of MEMS and commercial components significantly limited the sensor's cost.

Conclusions:

• The developed EFPI ultrasonic sensor is a cost-effective solution for high-sensitivity ultrasonic detection.
• This sensor shows significant potential for successfully detecting weak ultrasonic signals.
• The integrated manufacturing approach simplifies assembly and reduces production costs.