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Multidimensionální interferometrický odměřovací systém pro AFM mikroskopii - národní etalon pro nanometrologii
Hrabina, Jan
Příspěvek prezentuje výsledky výzkumu na interferometrickém odměřovacím 6-osém systému pro mikroskopii s lokální sondou. Zařízení bylo vyvíjeno ve spolupráci s Českým metrologickým institutem v Brně a je v sestavě s AFM mikroskopem (mikroskop atomárních sil) určeno k provozu jako národní nanometrologický etalon. Systém sestává z komerčního nanopolohovacího stolku řízeného piezoelektrickými aktuátory s možností polohování, metrologického rámu a laserem napájené interferometrické sestavy pro odměřování polohy ve všech šesti osách volnosti.
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Nanopositioning with detection of a standing wave
Holá, Miroslava ; Hrabina, Jan ; Číp, Ondřej ; Fejfar, A. ; Stuchlík, J. ; Kočka, J. ; Oulehla, Jindřich ; Lazar, Josef
A measuring technique is intended for displacement and position sensing over a limited range with detection of standing-wave pattern inside of a passive Fabry-Perot cavity. In this concept we consider locking of the laser optical frequency and the length of the Fabry-Perot cavity in resonance. Fixing the length of the cavity to e.g. a highly stable mechanical reference allows stabilizing wavelength of the laser in air and thus to eliminate especially the faster fluctuations of refractive index of air due to air flow and inhomogeneity. Detection of the interference maxima and minima within the Fabry-Perot cavity along the beam axis has been tested and proven with a low loss transparent photodetector with very low reflectivity. The transparent photodetector is based on a thin polycrystalline silicon layer. Reduction of losses was achieved thanks to a design as an optimized set of interference layers acting as an antireflection coating. The principle is demonstrated on an experimental setup.
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Interferometric coordinates measurement sytem for local probe microscopy nanometrology
Hrabina, Jan ; Lazar, Josef ; Klepetek, P. ; Číp, Ondřej ; Čížek, Martin ; Holá, Miroslava ; Šerý, Mojmír
We present an overview of new approaches to the design of nanometrology measuring system with a focus on methodology of nanometrology interferometric techniques and associated problems. The design and development of a nanopositioning setup with interferometric multiaxis monitoring and control involved for scanning probe microscopy techniques (primarily atomic force microscopy, AFM) for detection of the sample profile is presented. Coordinate position sensing allows upgrading the imaging microscope techniques up to quantified measuring. Especially imaging techniques in the micro- and nanoworld overcoming the barrier of resolution given by the wavelength of visible light are a suitable basis for design of measuring systems with the best resolution possible. The system is being developed in cooperation with the Czech metrology institute and it is intended to operate as a national nanometrology standard combining local probe microscopy techniques and sample position control with traceability to the primary standard of length.
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Precision displacement interferometry with stabilization of wavelength on air
Lazar, Josef ; Holá, Miroslava ; Hrabina, Jan ; Buchta, Zdeněk ; Číp, Ondřej
We present an interferometric technique based on differential interferometry setup for measurement in the subnanometer scale in atmospheric conditions. The motivation for development of this ultraprecise technique is coming from the field of nanometrology. The key limiting factor in any optical measurement are fluctuations of the refractive index of air representing a source of uncertainty on the 10'6 level when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined interferometric setup where a reference length is derived from a mechanical frame made from a material with very low thermal coefficient on the 1 O'8 level. The technique allows to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third represents a reference for stabilization of the wavelength of the laser source. The principle is demonstrated on an experimental setup and a set of measurements describing the performance is presented.
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Nanometrology coordinate measurement machines uncertainties caused by frequency fluctuations of the laser
Hrabina, Jan ; Lazar, Josef ; Číp, Ondřej
One of considerable sources of displacement measurement uncertainty in nanometrology systems such as multidimensional interferometric positioning for local probe microscopy is the influence of amplitude and especially frequency noise of a laser source which powers the interferometers. We investigated the noise properties of several laser sources suitable for interferometry for micro- and nano-CMMs (coordinate measurement machines) and compared the results with the aim to find the best option. The influences of amplitude and frequency fluctuations were compared together with the noise and uncertainty contributions of other components of the whole measuring system. Frequency noise of investigated laser sources was measured by two approaches – at first with the help of frequency discriminator (Fabry-Perot resonator) converting the frequency (phase) noise into amplitude one and then directly through the measurement of displacement noise at the output of the interferometer fringe detection and position evaluation. Both frequency noise measurements and amplitude noise measurements were done simultaneously through fast and high dynamic range synchronous sampling to have the possibility to separate the frequency noise and to compare the recorded results.
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Differential interferometry with suppression of the influence of refractive index of air for nanometrology
Holá, Miroslava ; Číp, Ondřej ; Hrabina, Jan ; Buchta, Zdeněk ; Lazar, Josef
We present an interferometric technique based on differential interferometry setup for measurement in the subnanometer scale in atmospheric conditions. The motivation for development of this ultraprecise technique is coming from the field of nanometrology. The key limiting factor in any optical measurement are fluctuations of the refractive index of air representing a source of uncertainty on the 1*E-6 level when evaluated indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined interferometric setup where a reference length is derived from a mechanical frame made from a material with very low thermal coefficient on the 1*E-8 level. The technique allows to track the variations of the refractive index of air on-line directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range acting as a tracking refractometer. The principle is demonstrated on an experimental setup and a set of measurements describing the performance is presented.
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Displacement Interferometry in Passive Fabry-Perot Cavity
Lazar, Josef ; Číp, Ondřej ; Oulehla, Jindřich ; Pokorný, Pavel ; Fejfar, Antonín ; Stuchlík, Jiří
We present techniques oriented to improvement of precision in incremental interferometric measurements of displacements over a limited range where the atmospheric wavelength of the coherent laser source is either directly stabilized to a mechanical reference or is corrected to fit to the reference. This may represent a reduction of uncertainty linking the laser wavelength not to indirectly evaluated refractive index but to the setup mechanics which cannot be completely eliminated. Here we suggest an approach where the traditional interferometers are replaced by a passive Fabry-Perot cavity with position sensing using an intracavity transparent photodetector.
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