Optically read Coriolis vibratory gyroscope based on a silicon tuning fork.

Area of Science:

• Mechanical Engineering
• MEMS Technology
• Sensor Technology

Background:

• Microelectromechanical systems (MEMS) gyroscopes are complex and often require integrated electronics.
• Existing Coriolis vibratory gyroscopes have limitations in excitation and readout methods.
• Miniature mechanical resonators offer potential for high-performance sensing.

Purpose of the Study:

• To design, fabricate, and characterize purely mechanical miniature resonating structures for gyroscopic applications.
• To demonstrate gyroscopic performance comparable to MEMS devices using a novel approach.
• To validate a fabrication process using wafer-level silicon processing.

Main Methods:

• Utilized differential optical readout, similar to atomic force microscopy's optical lever.
• Employed a piezoelectrically actuated stage for efficient excitation of tuning fork structures.
• Fabricated millimeter-scale tuning fork structures using high-throughput wafer-level silicon processing.

Main Results:

• Achieved reproducible responses to rotational rates as low as 1.8 x 10^3 °/h with a benchtop prototype.
• Demonstrated a noise-equivalent rate (ΩNER) <0.5 °/h for 10^3 s.
• Performance was not limited by thermomechanical noise despite low Q factors (<10^4) under ambient conditions.

Conclusions:

• Purely mechanical miniature resonators can achieve gyroscopic performance competitive with MEMS.
• The optical readout and piezoelectric excitation eliminate the need for on-chip electronics near the resonator.
• This proof-of-principle study shows significant potential, with performance four orders of magnitude from the fundamental limit.