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Fiber optic evanescent wave humidity sensor based on SiO2/TiO2 bilayer films
Applied Optics
|March 10, 2021
Summary
A novel silica/titania (SiO2/TiO2) bilayer thin-film fiber optic sensor offers enhanced humidity detection. This sensor exhibits rapid response and recovery times, alongside excellent stability for reliable environmental monitoring.
Area of Science:
- Materials Science
- Optical Engineering
- Environmental Sensing
Background:
- Fiber optic sensors are crucial for environmental monitoring.
- Developing highly sensitive and stable humidity sensors is an ongoing challenge.
Purpose of the Study:
- To fabricate a SiO2/TiO2 bilayer thin-film fiber optic humidity sensor.
- To evaluate the sensor's sensitivity, response time, recovery time, and stability.
Main Methods:
- Modified dip coating process for SiO2/TiO2 bilayer deposition on an optical fiber core.
- Measurement of relative humidity (RH) via transmitted laser intensity modulation at room temperature.
Main Results:
- The sensor demonstrated two-segmented linearity with sensitivities of 5.35 µW/% RH (15%-50% RH) and 1.94 µW/% RH (50%-95% RH).
- Achieved superior response time (25 s) and recovery time (50 s) compared to existing intensity modulation fiber optic humidity sensors.
- Exhibited good reproducibility and long-term stability.
Conclusions:
- The SiO2/TiO2 bilayer sensor provides a promising platform for accurate and efficient humidity sensing.
- The sensing mechanism involves moisture-induced changes in the SiO2 film's refractive index and absorption coefficient, modulating evanescent waves.
