Interferometric technique for measuring the refractive index variation of a liquid with temperature

Area of Science:

• Optics and Photonics
• Physical Chemistry
• Fluid Dynamics

Background:

• Accurate measurement of liquid refractive index is crucial for various scientific and industrial applications.
• Traditional methods face challenges in achieving uniform temperature distribution and rapid temperature changes.
• Mach-Zehnder interferometry offers high sensitivity but requires precise control over sample conditions.

Purpose of the Study:

• To develop and validate a novel technique for measuring refractive index variations in liquids.
• To overcome the limitations of uniform temperature control in optical path measurements.
• To determine the temperature-dependent refractive index of a dilute NaCl solution.

Main Methods:

• A Mach-Zehnder interferometer was employed for refractive index measurements.
• A new method was developed involving heating liquid in a separate vessel and injecting it as jets into the test cell.
• This turbulent mixing approach ensures uniform temperature distribution and allows for rapid temperature variation.

Main Results:

• The developed technique achieved an equivalent resolution of 2x10^-6 in refractive index variation.
• The method successfully measured the refractive index variation of a 0.1% NaCl/H2O solution.
• Measurements were conducted over a temperature range of 23-33 degrees C.

Conclusions:

• The novel jet injection method effectively addresses the challenge of uniform temperature control in optical measurements.
• The technique provides high-resolution data for studying liquid properties as a function of temperature and concentration.
• This method offers a reliable approach for characterizing the optical properties of solutions.