Nano-displacement measurement using a Littman-configured interferometer based on orbital angular momentum beams

Area of Science:

• Optics and Photonics
• Nanotechnology
• Metrology

Background:

• Precise measurement of nano-displacements is crucial for advanced manufacturing and scientific research.
• Traditional interferometers face limitations in environmental robustness and resolution.

Purpose of the Study:

• To develop a Littman-configured interferometer utilizing orbital angular momentum (OAM) beams for high-resolution nano-displacement measurement.
• To investigate the system's capability for both in-plane and out-of-plane displacement detection.

Main Methods:

• Generation of petal-like interferograms via interference of conjugate OAM beams.
• Diffraction of a reference OAM beam from a scale grating to create a measured beam.
• Demodulation of interferogram rotation angle using circular cross-correlation for displacement calculation.

Main Results:

• Theoretical analysis shows 1° interferogram rotation corresponds to 2.313 nm in-plane and 1.067 nm out-of-plane displacement.
• Experimental results demonstrate maximum errors of 1.299 nm (in-plane) and 1.898 nm (out-of-plane).
• Achieved displacement resolutions better than 2 nm for both measurement types.

Conclusions:

• The OAM interferometer in a Littman configuration effectively transfers the measurement standard to the grating pitch for in-plane measurements.
• Out-of-plane displacement is influenced by both grating pitch and wavelength.
• The proposed method offers enhanced environmental robustness and high displacement resolution.