Solving Fresnel equation for refractive index using reflected optical power obtained from Bessel beam interferometry

Area of Science:

• Optical Physics
• Metrology
• Biomedical Optics

Background:

• Refractive index (RI) is a crucial parameter in various scientific and industrial fields.
• Accurate and non-invasive RI measurement techniques are essential for quality control and research.
• Existing optical fiber-based RI sensors often require temperature compensation, limiting their practical application.

Purpose of the Study:

• To demonstrate an interferometric technique for non-invasive refractive index measurement of liquid samples.
• To validate the use of Fresnel equations with optical interferometry for RI determination.
• To develop a temperature-independent RI sensing method suitable for industrial processes.

Main Methods:

• Utilized low-coherence common-path optical interferometry with a specialized optical fiber tip.
• Generated a non-diffractive Bessel beam to probe liquid samples non-invasively within a glass container.
• Employed fast-Fourier transform (FFT) analysis of interference spectra to determine reflected powers and solve Fresnel equations for RI.

Main Results:

• Successfully measured the refractive index of various liquid samples, including turbid media like blood.
• Demonstrated the feasibility of using reflected power measurements from dielectric interfaces to calculate RI.
• Validated the technique as a confirmation of the Fresnel equation for light reflection.

Conclusions:

• The developed non-invasive interferometric technique accurately measures the refractive index of liquids without requiring temperature compensation.
• This method offers a robust and potentially cost-effective solution for real-time RI monitoring in pharmaceutical and chemical industries.
• The technique serves as an excellent example for confirming the Fresnel equation in practical optical measurements.