A miniature fiber optic refractive index sensor built in a MEMS-based microchannel

Area of Science:

• Optical Physics
• Nanotechnology
• Sensor Technology

Background:

• Refractive index (RI) sensing is crucial for various applications.
• Existing sensors may lack sensitivity, immunity to electromagnetic interference (EMI), or scalability.
• Fabry-Perot (FP) interferometers offer potential for high-performance sensing.

Purpose of the Study:

• To develop a small, highly sensitive, and EMI-immune RI sensor.
• To utilize microelectromechanical systems (MEMS) for precise fabrication.
• To demonstrate a novel method for RI measurement via phase shift demodulation.

Main Methods:

• Fabrication of an FP cavity using metal-deposited single-mode optical fiber endfaces within a silicon microchannel.
• Utilizing MEMS techniques (photolithography, deep dry etching) for microchannel fabrication with 2 μm accuracy.
• Demodulating the transmission spectrum phase shift to determine RI changes.

Main Results:

• Achieved a sensor sensitivity of 665.90 nm/RIU.
• Demonstrated a limit of detection of 6 × 10⁻⁶ RIU.
• Verified EMI immunity and high finesse due to metal film mirrors.

Conclusions:

• The developed FP interferometer sensor is highly sensitive and EMI-immune.
• MEMS fabrication enables precise control and potential for high-yield mass production.
• Integration of multiple sensors on a chip allows for simultaneous multi-parameter measurements (RI, temperature, biomolecules).