10-pm-order mechanical displacement measurements using heterodyne interferometry

Area of Science:

• Metrology and Measurement Science
• Optical Engineering
• Nanotechnology

Background:

• Measuring sub-10-picometer mechanical displacements is challenging due to inherent electronic and environmental noise.
• Conventional interferometry systems require significant noise floor improvements for ultra-precise measurements.

Purpose of the Study:

• To develop and demonstrate a system capable of 10-picometer (pm)-order mechanical displacement measurements.
• To investigate the impact of environmental factors (air vs. vacuum) on measurement precision.
• To achieve a low noise floor for enhanced phase meter performance.

Main Methods:

• Utilized a single-path heterodyne interferometer with two spatially separated beams and balanced optical arms.
• Implemented a phase meter with a phase-locked loop (PLL) algorithm programmed on a field-programmable gate array (FPGA) for noise reduction.
• Integrated the interferometer with a stiff piezoelectric flexure stage within a vacuum chamber for environmental control.

Main Results:

• Achieved mechanical displacement measurements with an 11-picometer (pm) precision in both air and vacuum environments.
• Demonstrated a noise floor of 0.2 pm/√Hz within the 50 Hz to 100 Hz frequency range in vacuum.
• Validated the effectiveness of the PLL algorithm and vacuum environment in reducing noise.

Conclusions:

• The developed heterodyne interferometry system, coupled with PLL-based noise reduction and vacuum operation, successfully achieves 10-pm-order displacement measurements.
• The system exhibits high precision and a low noise floor, making it suitable for advanced metrology applications.
• Environmental isolation and advanced signal processing are critical for pushing the boundaries of precision measurement.