Directly traceable ultra-precision displacement metrology: a heterodyne self-traceable grating interferometer

Area of Science:

• Metrology
• Optical Engineering
• Nanotechnology

Background:

• Heterodyne grating interferometers offer high resolution and environmental adaptability for precise displacement measurement.
• Current methods lack direct traceability for grating pitch, leading to measurement inaccuracies and inconsistencies.
• Self-traceable gratings (STG) fabricated via atomic lithography provide picometre-level accuracy and direct traceability to atomic transition frequencies.

Purpose of the Study:

• To develop a novel heterodyne self-traceable grating interferometer (He-STGI) for ultra-precision displacement metrology.
• To combine stable heterodyne interferometric length metrology with intrinsically traceable displacement readout.
• To establish a simplified and shortened traceability chain for displacement calibration.

Main Methods:

• Fabrication of self-traceable gratings (STG) using atomic lithography technology with 4700 lines/mm density.
• Development of a heterodyne self-traceable grating interferometer (He-STGI) integrating STG.
• Experimental validation against a traceable iodine-stabilized laser interferometer (IS-LI).

Main Results:

• The He-STGI demonstrated 2-nm-level resolution.
• Achieved a standard deviation of 1.23 nm over a 2-min static record.
• Showcased approximately 0.5 nm deviation in dynamic displacement repeatability.

Conclusions:

• The proposed He-STGI offers a novel solution for ultra-precision displacement metrology.
• Intrinsically traceable displacement readout enhances measurement accuracy and consistency.
• The He-STGI simplifies and shortens the traceability chain for displacement calibration.