2.4 ng/√Hz low-noise fiber-optic MEMS seismic accelerometer

Area of Science:

• Microelectromechanical Systems (MEMS)
• Optical Sensing
• Seismology

Background:

• Development of sensitive accelerometers is crucial for seismic exploration.
• Existing micromachined optical accelerometers face limitations in noise performance.
• Fiber-optic sensors offer potential advantages in harsh environments.

Purpose of the Study:

• To introduce a novel fiber-optic MEMS seismic-grade accelerometer.
• To demonstrate a fabrication process using composite masking for deep reactive ion etching.
• To evaluate the noise performance and sensitivity of the developed accelerometer.

Main Methods:

• Fabrication of a silicon flexure accelerometer using bulk silicon processing.
• Utilized photoresist/silicon dioxide composite masking for one-step deep reactive ion etching.
• Employed a Fabry-Perot interference (FPI) based light intensity detection for displacement transduction.

Main Results:

• Achieved an overall noise floor of 2.4 ng/√Hz at 10 Hz.
• Demonstrated a sensitivity of 3165 V/g.
• The optical displacement transduction system exhibited a noise floor of 208 fm/√Hz at 10 Hz.

Conclusions:

• The developed fiber-optic MEMS accelerometer shows superior noise performance compared to many micromachined optical accelerometers.
• The fabrication method using composite masking is effective for creating complex MEMS structures.
• The sensor is highly promising for high-performance seismic exploration applications.