High-Sensitivity Seawater Refraction Index Optical Measurement Sensor Based on a Position-Sensitive Detector

Area of Science:

• Oceanography
• Optical Physics
• Sensor Technology

Background:

• Accurate measurement of seawater refractive index is crucial for ocean observation.
• Existing methods may lack the required precision for certain applications.
• High-precision refractive index data aids in understanding oceanographic phenomena.

Purpose of the Study:

• To develop and validate a highly sensitive method for measuring the refractive index of seawater.
• To establish a theoretical model correlating laser spot displacement with refractive index changes.
• To explore the system's potential for underwater vehicle wake detection.

Main Methods:

• Utilizing a position-sensitive detector (PSD) and laser beam deflection principles.
• Developing a theoretical model for laser spot displacement analysis.
• Incorporating a focusing lens to enhance refractive index detection sensitivity.
• Calibrating the system using the known relationship between seawater refractive index and underwater pressure (depth).

Main Results:

• The developed system achieved a sensitivity of 9.93×10-9 refractive index units (RIU).
• The refractive index deviation due to system stability was determined to be ±7.54×10-9 RIU.
• Experimental results verified the feasibility of highly sensitive seawater refractive index measurement.

Conclusions:

• The proposed method offers a feasible and highly sensitive approach for seawater refractive index measurement.
• The system's sensitivity surpasses the refractive index changes caused by underwater vehicle wakes.
• Potential applications include ocean observation, underwater vehicle wake measurement, and monitoring of underwater navigation targets.