A heterodyne interferometer with periodic nonlinearities smaller than ±10 pm

Weichert, Christoph; Köchert, Paul; Köning, Rainer; Flügge, Jens; Andreas, Birk; Kuetgens, U.; Yacoot, Andrew

doi:10.1088/0957-0233/23/9/094005

Cited by 74 publications

(52 citation statements)

References 17 publications

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“…Residual phase noise as from the source (AOMs, fibers) will be suppressed by pick-up of an optical heterodyne reference signal close to the balanced interferometers. Limited polarization extinction of PMF requires high quality polarization clean-up after fiber delivery to the bench in order to benefit from the spatially separated heterodyne source delivery and avoid [13]. In spite of conceptual immunity against thermal expansion of the interferometer bench, any practical implementation will, supposedly, require also excellent thermal stability beyond the ±0.1 ºC stability of the VSL laboratory.…”

Section: Icso 2012mentioning

confidence: 99%

Dimensional stability validation and sensor calibration with sub-nanometer accuracy

Voigt

Bergmans

2017

International Conference on Space Optics — ICSO 2012

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Abstract-We report on the development of measurement facilities for the calibration of ultra-precision displacement sensors and for the dimensional stability validation of materials, joint structures and sensors. A Fabry-Pérot interferometer and a double-ended heterodyne interferometer are discussed, both with a dedicated design aiming for sub-nanometer displacement measurement accuracy.Optical metrology; dimensional stability; sensor calibration; displacement interferometry

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Section: Icso 2012mentioning

confidence: 99%

Dimensional stability validation and sensor calibration with sub-nanometer accuracy

Voigt

Bergmans

2017

International Conference on Space Optics — ICSO 2012

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“…It was already proven that a newly developed optical interferometer of the PTB achieved residual periodic non-linearity deviations, which are considered to provide the dominating uncertainty contribution below 10 pm [10], see fig. 7.…”

confidence: 99%

Challenges in nanometrology: high precision measurement of position and size

Bosse

Bodermann

Dai

et al. 2015

Tm - Technisches Messen

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This contribution describes recent developments of the PTB in high precision position and size metrology as support for different nanotechnology applications. It will be shown how measurement uncertainties of about 1-2 nm for 1D-position of graduation lines on 152 mm photomasks (6''), or on line scales and incremental encoders of about 300 mm length have been achieved. The measurement of the size of nanoscale features represents additional challenges, because in addition to the length metric, also the location of opposite feature edges has to be precisely determined. In addition to other feature size or CD metrology techniques applied at PTB, a recent development which uses transmission electron microscopy in the traceability chain of AFM CD measurements will be described. The uncertainties achieved for CD measurements on high quality Si line structures are U 95% = 1.6 nm.

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“…This can be achieved by keeping the two source frequencies spatially separated throughout the interferometer system until detection takes place [12][13][14][15][16][17][18][19]. Spatial separation prevents frequency leakage occurring, thereby prohibiting PNL, but it also leads to possible optical path length inequality during source frequency delivery.…”

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confidence: 99%

“…Spatial separation prevents frequency leakage occurring, thereby prohibiting PNL, but it also leads to possible optical path length inequality during source frequency delivery. The limitation of these interferometer configurations is their special and often complicated optical layouts [18] that limit their applicability.…”

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confidence: 99%

Heterodyne displacement interferometer, insensitive for input polarization

Meskers¹,

Spronck²,

Schmidt³

2014

Opt. Lett.

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Periodic nonlinearity (PNL) in displacement interferometers is a systematic error source that limits measurement accuracy. The PNL of coaxial heterodyne interferometers is highly influenced by the polarization state and orientation of the source frequencies. In this Letter, we investigate this error source and discuss two interferometer designs, designed at TU Delft, that showed very low levels of PNL when subjected to any polarization state and/or polarization orientation. In the experiments, quarter-wave plates (qwps) and half-wave plates (hwps) were used to manipulate the polarization state and polarization orientation, respectively. Results from a commercial coaxial system showed first-order PNL exceeding 10 nm (together with higher order PNL) when the system ceased operation at around 15°hwp rotation or 20°qwp rotation. The two "Delft interferometers," however, continued operation beyond these maxima and obtained first-order PNLs in the order of several picometers, without showing higher order PNLs. The major advantage of these interferometers, beside their high linearity, is that they can be fully fiber coupled and thus allow for a modular system buildup. Laser interferometry is an often applied measurement method in several fields of research, since it allows for noncontact measurements. It is especially preferred in the field of metrology, because of its direct traceability to the length standard [1]. Interferometry is also used in lithography machines in the semiconductor industry, gravitational wave detection [2], coordinate measuring machines, and as a calibration tool for other measurement devices, such as capacitive sensors, inductive sensors, and optical encoders. Many types of displacement interferometer systems can be distinguished; this publication deals with heterodyne displacement interferometry using a stabilized He-Ne laser (λ 632.8 nm) combined with two acoustooptic modulators for generating two (fixed-offset) source frequencies.Industrial manufacturing processes currently operate with measurement errors at the subnanometer level and will require even smaller errors in the near future [3]. When operating at this level, a heterodyne interferometer system is hampered by many error sources. The main error sources are the frequency stability of the laser source, noncommon optical pathway variations due to variations in the refractive indices of optical transport media, system alignment (i.e., cosine error, Abbé error), optical wavefront quality combined with beam walkoff [4], and periodic nonlinearity (PNL) in the measured phase [5][6][7][8][9][10]. Operating in vacuum will improve the obtained measurement error. However, PNL in the measurand remains a substantial error source.PNL manifests itself primarily in traditional heterodyne systems with coaxial beams. Such beams contain two linearly polarized frequencies that are orthogonally oriented. These frequencies may mix (due to "frequency leakage"), resulting in periodic errors that are superimposed on the obtained displacement data. This type ...

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A heterodyne interferometer with periodic nonlinearities smaller than ±10 pm

Cited by 74 publications

References 17 publications

Dimensional stability validation and sensor calibration with sub-nanometer accuracy

Dimensional stability validation and sensor calibration with sub-nanometer accuracy

Challenges in nanometrology: high precision measurement of position and size

Heterodyne displacement interferometer, insensitive for input polarization

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