Refractive index sensing with temperature compensation by a multimode-interference fiber-based optical frequency comb...

Area of Science:

• Optics and Photonics
• Sensing Technology
• Analytical Chemistry

Background:

• Refractive index (RI) sensing is crucial for monitoring concentrations in various applications.
• Temperature fluctuations can significantly affect RI measurements, necessitating compensation.
• Existing methods often lack simultaneous RI and temperature measurement capabilities.

Purpose of the Study:

• To propose and demonstrate a novel sensing method for simultaneous refractive index (RI) and temperature measurement.
• To develop a sensing cavity based on an optical frequency comb (OFC) and multimode-interference (MMI) fiber.
• To achieve accurate and continuous monitoring of liquid concentration and temperature.

Main Methods:

• Utilized a multimode-interference (MMI) fiber integrated with an optical frequency comb (OFC) to create the MMI-OFC sensing cavity.
• Simultaneously measured material-dependent RI and sample temperature by analyzing the comb spacing frequency shift and the wavelength shift of the OFC.
• Realized continuous measurement of RI-related concentration and temperature of liquid samples.

Main Results:

• Achieved simultaneous and continuous measurement of RI-related concentration and temperature.
• Demonstrated high precision with 1.6 × 10^-4 RIU for RI and 0.08 °C for temperature.
• The MMI-OFC sensing cavity effectively compensates for temperature variations in RI measurements.

Conclusions:

• The proposed MMI-OFC sensing cavity provides a robust solution for simultaneous RI and temperature sensing.
• This method enables precise, continuous monitoring essential for various analytical applications.
• The developed technique offers a valuable tool for applications requiring accurate RI sensing with temperature compensation.