Refractive-index measurement at high spatial resolution by source doubling.

Area of Science:

• Optics and Photonics
• Materials Science
• Metrology

Background:

• Accurate measurement of material properties like refractive index is crucial for various scientific and industrial applications.
• Existing techniques may lack the resolution or adaptability for thin solid samples.

Purpose of the Study:

• To introduce and validate a new interferometric technique for measuring the refractive index of thin solid samples.
• To achieve submillimetric spatial resolution in refractive index measurements.

Main Methods:

• Utilized a modified triangular common path interferometer for source doubling, generating a spatially distributed interferogram.
• Employed a CCD line sensor to detect fringe spacing changes.
• Inserted the thin solid sample into the optical path to alter the distance between secondary point sources.

Main Results:

• Successfully measured the refractive index of a microscope slide at 632.8 nm.
• Achieved a spatial resolution of 150-microm probe spots.
• Demonstrated the technique's ability to determine refractive index by measuring fringe spacing alterations.

Conclusions:

• The developed interferometric technique offers a precise and high-resolution method for determining the refractive index of thin solid samples.
• The technique's resolution is influenced by the primary source size and probe spot-forming lens magnification.
• This method provides a valuable tool for material characterization in scientific research and development.