Spectrometer-based refractive index and dispersion measurement using low-coherence interferometry with confocal...

Area of Science:

• Optical Physics
• Metrology
• Materials Science

Background:

• Accurate characterization of optical materials is essential for various applications.
• Traditional methods for measuring refractive index and thickness can be complex and time-consuming.

Purpose of the Study:

• To develop and validate a novel fiber-optic low-coherence interferometer.
• To enable simultaneous measurement of phase refractive index (nₚ), group refractive index (n<0xE2><0x82><0x97>), and geometrical thickness (t) of transparent plates.
• To assess the material dispersion properties.

Main Methods:

• Utilizing a fiber-optic low-coherence interferometer with a broadband light source.
• Measuring quantities related to phase and group refractive indices.
• Measuring the dispersion of phase index dependent quantities across a range of wavelengths.
• Relating measured quantities to simultaneously determine nₚ, n<0xE2><0x82><0x97>, and t.

Main Results:

• Successfully measured refractive indices and thickness for various transparent materials.
• Achieved high precision with mean percentage errors of 0.09% for nₚ, 0.08% for n<0xE2><0x82><0x97>, and 0.11% for t.
• Demonstrated capability to measure ordinary and extraordinary refractive indices of birefringent materials, such as sapphire.

Conclusions:

• The developed fiber-optic interferometer provides a precise and efficient method for characterizing transparent optical materials.
• The technique is versatile and applicable to a wide range of materials, including birefringent ones.
• This method offers significant improvements in accuracy for optical metrology.