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16:11
Implementation of a Reference Interferometer for Nanodetection
Published on: April 26, 2014
Heterodyne interferometer with subatomic periodic nonlinearity
C M Wu1, J Lawall, R D Deslattes
1Physics Laboratory, National Institute of Standards and Technology, Building 221, Room A141, Gaithersburg, Maryland 20899, USA.
Applied Optics
|March 8, 2008
Summary
A novel heterodyne interferometer eliminates periodic nonlinearity for precise differential displacement measurements. This new design achieves sub-20 picometer nonlinearity, overcoming limitations of traditional methods.
Area of Science:
- Optics and Photonics
- Metrology
- Precision Engineering
Background:
- Traditional heterodyne interferometers often suffer from periodic nonlinearity, limiting measurement accuracy.
- Zeeman split lasers are a common source of this nonlinearity in conventional designs.
Purpose of the Study:
- To present a new heterodyne interferometer design for differential displacement measurements.
- To overcome the inherent periodic nonlinearity found in traditional interferometers.
- To achieve theoretically perfect immunity from common-mode displacement.
Main Methods:
- Utilized two acousto-optic modulators to generate spatially separated light beams with different frequencies.
- Employed laser beams of the same frequency in both the measurement and reference arms.
- Experimentally validated the performance and residual nonlinearity of the developed interferometer.
Main Results:
- Demonstrated a novel heterodyne interferometer design that is, in principle, free of periodic nonlinearity.
- Achieved a residual level of periodic nonlinearity less than 20 picometers in amplitude.
- Identified unbalanced ghost reflections as the cause of the remaining, slowly drifting periodic error.
Conclusions:
- The proposed heterodyne interferometer design effectively minimizes periodic nonlinearity for differential displacement measurements.
- The use of acousto-optic modulators and identical frequency beams in arms significantly reduces systematic errors.
- Further improvements can be made by addressing unbalanced ghost reflections for even higher precision.
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