Measurement of refractive index change with temperature using thermal self-phase modulation

Area of Science:

• Optics and Photonics
• Laser-Material Interactions
• Physical Chemistry

Background:

• Thermal self-phase modulation (TSPM) is a nonlinear optical phenomenon.
• It arises from laser-induced temperature gradients affecting refractive index.
• Accurate measurement of optical properties in liquids is crucial for various applications.

Purpose of the Study:

• To utilize TSPM for measuring the product of absorption coefficient and the change in refractive index with temperature (dn/dT).
• To develop a method for independently determining dn/dT in absorbing liquids.
• To evaluate the feasibility and limitations of this TSPM-based technique.

Main Methods:

• Employing a laser beam passing through an absorbing liquid sample.
• Introducing a dye to precisely quantify the absorption coefficient.
• Analyzing the resulting thermal self-phase modulation to deduce optical parameters.

Main Results:

• Successfully measured the product of absorption coefficient and dn/dT in several liquids.
• Demonstrated that adding a dye enables independent determination of dn/dT.
• Presented experimental results and discussed the advantages and disadvantages of the method.

Conclusions:

• TSPM offers a viable method for characterizing optical properties of absorbing liquids.
• The addition of dye significantly enhances the precision of dn/dT measurements.
• This technique provides valuable insights into laser-matter interactions in liquid media.