Refractive index profile measurement techniques by reflectivity profiling: vidicon imaging, beam scanning, and sample...

Area of Science:

• Optoelectronics
• Materials Science
• Photonics

Background:

• Titanium-diffused lithium niobate (LiNbO3) is a key material for integrated optics.
• Accurate characterization of refractive index profiles is crucial for waveguide performance.

Purpose of the Study:

• To develop and compare methods for directly determining refractive index profiles.
• To establish a precise measurement technique for LiNbO3 waveguides.

Main Methods:

• Reflectivity measurements on angular polished surfaces of LiNbO3 waveguides.
• Comparison of three techniques: large area illumination, focused beam scanning, and sample scanning.
• Detailed analysis of the preferred sample scanning method.

Main Results:

• The sample scanning method offers high accuracy (Deltan/n = 10(-4)).
• Achieved local resolution of <0.1 microm in depth and ~1 microm in width.
• Demonstrated direct determination of refractive index profiles.

Conclusions:

• The reflectivity measurement technique is effective for characterizing LiNbO3 waveguides.
• The scanning method provides superior accuracy and resolution for index profiling.
• This method is valuable for optimizing waveguide fabrication and performance.