Abstract
A fractional error as large as 25 pm at the zero optical-path difference has been observed in an optical interferometer measuring the displacement of an x-ray interferometer used to determine the lattice parameter of silicon. Detailed investigations have brought to light that the error was caused by light forward-scattered from the beam feeding the interferometer. This paper reports on the impact of forward-scattered light on the accuracy of two-beam optical interferometry applied to length metrology, and supplies a model capable of explaining the observed error.
Highlights
A fractional error as large as 25 pm mm−1 at the zero optical-path difference has been observed in an optical interferometer measuring the displacement of an x-ray interferometer used to determine the lattice parameter of silicon
This paper reports on the impact of forward-scattered light on the accuracy of two-beam optical interferometry applied to length metrology, and supplies a model capable of explaining the observed error
Laser interferometry is widely used in dimensional metrology
Summary
Laser interferometry is widely used in dimensional metrology. The ability to deliver high-bandwidth, low-noise, sensitive and accurate position and angle information allows interferometers to be used in precision measurements and feedback loops. Exemplar applications include measurements of the Planck [1] and Avogadro constants [2], free-fall gravimetry [3], γ-ray spectrometry [4], and the detection of gravitational waves [5]. All these measurements require state-of-the-art investigations of the interferometer operation as regards the impact of, among others, diffraction [6,7,8], wavefront stability and errors [9], beam alignment [10, 11], ghost, stray and recycled light [12], and polarization delivery [4, 13]. Parasitic rotations and transverse motions are sensed via laser interferometry and a capacitive transducer; feedback loops provide picometer positioning, nanoradian alignment, and nanometer straightness
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