Nanoscale surface metrology with a liquid crystal-based phase-shifting angular shearing interferometer

Area of Science:

• Optical metrology
• Interferometry
• Liquid Crystal applications

Background:

• Optical surface metrology (SM) requires precise measurement techniques.
• Existing interferometry methods can be complex to analyze.
• Liquid crystals (LCs) offer tunable optical properties.

Purpose of the Study:

• To propose and demonstrate a phase-shifting angular shearing interferometer for SM.
• To utilize a liquid crystal cell for phase shifting and polarization control.
• To validate the technique for step height measurement.

Main Methods:

• Development of an angular shearing interferometer using a wedge-shaped LC cell and polarization phase shifter.
• Application of a phase-shifting technique with four phase-shifted interferograms.
• Analysis using a simplified Wiener deconvolution method for shearing interferograms.
• Validation through simulation and experimental step height measurement.

Main Results:

• Successful demonstration of the interferometer for step height measurement.
• Experimental accuracy of 5.56% for step height determination.
• Agreement of results with atomic force microscopy (AFM) measurements.
• Validation of the simplified Wiener deconvolution method for interferogram analysis.

Conclusions:

• The proposed LC-based angular shearing interferometer is effective for optical surface metrology.
• The technique offers accurate step height measurement with tunable spatial resolution.
• The simplified analysis method is efficient for shearing interferograms.