Measuring picometre-level displacements using speckle patterns produced by an integrating sphere

Area of Science:

• Physics
• Optical Engineering
• Metrology

Background:

• Advancements in optical microscopy, semiconductor technology, and fundamental science necessitate precision sensing at the nanoscale.
• There is a growing need for displacement and position sensors capable of sub-nanometer accuracy.

Purpose of the Study:

• To demonstrate a novel method for highly sensitive sub-nanometer displacement sensing.
• To utilize light speckle patterns within an integrating sphere as a probe for nanoscale motion.

Main Methods:

• An integrating sphere was divided into two independent hemispheres, with one hemisphere designed for controlled movement.
• The relative motion between hemispheres was analyzed by observing changes in the generated light speckle pattern.
• Analytical methods were employed to infer displacement amplitude from speckle pattern variations.

Main Results:

• The developed method achieved a noise floor of 5 picometers per root Hertz (pm/rtHz) above 30 Hz.
• The technique successfully measured oscillations with an amplitude of 17 picometers (pm).
• A signal-to-noise ratio of 3 was achieved for the measured oscillations.

Conclusions:

• Speckle patterns from light reflections inside an integrating sphere offer a highly sensitive method for displacement sensing.
• The facile implementation allows for precise measurement of sub-nanometer displacements, crucial for nanoscale applications.
• This technique provides a viable solution for demanding precision sensing requirements in advanced scientific fields.