Gaussian Beams and Spatial Modulation in Nanopositioning

The kilogram is the last base unit of the systeme international d'unites (SI) that is still defined by an artifact. The watt-balance experiment is one of the promising methods that can produce a new definition of the kilogram based on fundamental constants. In this experiment, to compare an ele...

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Bibliographic Details
Published in:IEEE transactions on instrumentation and measurement 2009-04, Vol.58 (4), p.1003-1009
Main Authors: Haddad, D., Juncar, P., Geneves, G., Wakim, M.
Format: Article
Language:English
Subjects:
Amplifiers
Astrophysics
Beams
Beams (radiation)
Collimators
Constants
Electromagnetic forces
Electromagnetic propagation
Gaussian beams
Gaussian beams (optics)
Gravity
Instrumentation
Modulation
Nanopositioning
Nanostructure
Optical modulation
position control
position measurement
Slits
spatial light modulators
Spatial resolution
synchronous detection
Uncertainty
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Summary:The kilogram is the last base unit of the systeme international d'unites (SI) that is still defined by an artifact. The watt-balance experiment is one of the promising methods that can produce a new definition of the kilogram based on fundamental constants. In this experiment, to compare an electromagnetic force and a gravitational force with a relative uncertainty of 10 -9 by means of a beam balance, an absolute position sensor with nanometric resolution is needed. A novel method in position sensing based on the Gaussian beam propagation properties and their spatial modulation is presented. Two modulated and collimated Gaussian beams are focused into a slit. The slit is fixed to the object to be positioned. The resulting beams at the slit illuminate a photodetector whose signal is demodulated by a lock-in amplifier. The lock-in amplifier output signal is a function of the slit position with respect to the two modulated Gaussian beams. A resolution of 25 pm/(Hz) 1/2 can be achieved. The long-term stability is 3.5 pm over 2 h and 20 min.
ISSN:0018-9456
1557-9662
DOI:10.1109/TIM.2008.2008475