All-sapphire-based fiber-optic pressure sensor for high-temperature applications based on wet etching

Area of Science:

• Materials Science
• Optical Sensors
• Nanotechnology

Background:

• Extrinsic Fabry-Perot interferometer (EFPI) sensors are crucial for precise pressure measurements.
• Sapphire is a promising material for sensor fabrication due to its robust properties.
• Improving interference signal quality in EFPI sensors is essential for enhanced performance.

Purpose of the Study:

• To develop an all-sapphire EFPI pressure sensor with improved interference signal quality.
• To investigate the effect of wet etching parameters on sapphire pressure sensitive diaphragm (SPSD) surface roughness.
• To demonstrate the performance benefits of a smoother SPSD surface.

Main Methods:

• Fabrication of sapphire pressure sensitive diaphragms (SPSDs) using wet etching with varying H3PO4 and H2SO4 ratios at 280°C.
• Characterization of SPSD surface roughness.
• Construction of a pressure sensing test system utilizing SPSDs with different surface roughness values (3.91nm and 0.39nm).
• Comparative performance testing of the EFPI pressure sensors.

Main Results:

• Achieved SPSD surface roughness values of 3.91nm (H3PO4:H2SO4 ratio 1:1) and 0.39nm (ratio 1:3).
• The EFPI sensor with a 0.39nm surface roughness SPSD demonstrated significant improvements.
• Demodulation jumps were eliminated, and cavity length fluctuation was reduced to ±5nm.

Conclusions:

• Optimized wet etching of sapphire can yield ultra-smooth surfaces for EFPI pressure sensors.
• Reduced surface roughness of the SPSD is critical for high-quality interference signals and stable sensor performance.
• The developed all-sapphire EFPI pressure sensor offers a promising solution for demanding pressure sensing applications.