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Accurate Picometers for DC and Low-Frequency Displacement Measurement



Jon R. Pratt, Douglas T. Smith, Lowell Howard


We have developed a fiber-optic interferometer optimized for best performance in the frequency range from DC to 1 kHz, with displacement linearity of 1 % over a range of 25 nm, and noise-limited resolution of 2 pm [1]. The interferometer uses a tunable infrared laser source (nominal 1550 nm wavelength) with high amplitude and wavelength stability, low spontaneous self-emission noise, high sideband suppression and a coherence control feature that broadens the laser linewidth and dramatically lowers the low-frequency noise in the system. The amplitude stability of the source, combined with the use of specially manufactured bend-insensitive fiber and all-spliced fiber construction, result in a robust homodyne interferometer system that achieves resolution of 40 fm Hz-1/2 above 20 Hz and approaches the shot-noise-limit of 20 fm Hz-1/2 at 1 kHz for an optical power of 10 μW, without the need for differential detection. Here we briefly review the design and construction of the interferometer, demonstrate its use for feedback stabilization of a probe displacement, and suggest a method to link the interferometer output to an absolute wavelength reference with an uncertainty on the order of 0.5% for displacements on the order of 100 pm.
Conference Dates
April 6-7, 2009
Conference Location
Albuquerque, NM
Conference Title
ASPE 2009 Spring Topical Meeting Mechanical Metrology and Measurement Uncertainty


picometer, fiberoptic, interferometer


Pratt, J. , Smith, D. and Howard, L. (2009), Accurate Picometers for DC and Low-Frequency Displacement Measurement, ASPE 2009 Spring Topical Meeting Mechanical Metrology and Measurement Uncertainty, Albuquerque, NM, [online], (Accessed June 18, 2024)


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Created April 6, 2009, Updated February 19, 2017