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Laser standards for interferometry and stable frequencies distribution
Hrabina, Jan
Optical frequency references - absorption cells - represent an unique tool for frequency stabilization of the laser sources. Their spectral properies define overall quality of the stabilized laser, so these properties must be precisely controlled and verified. One of the most used absorption media in the visible spectral range is molecular iodine. It offers wide and reach spectra of very narrow and strong transitions so many types of laser standards can be realized on base of this media. Testing of final properties of iodine absorption cells is traditionaly based on two methods - laser induced fluorescence method (LIF) and evaluation of absolute frequency shifts of the iodine stabilized laser (beatnote measurement). Unfortunately both of these methods have few limitations and disadvantages - in case of high-quality cells the LIF method reaches its resolution limits, the beatnote method needs quite complicated optical setup. We present a novel approach for the iodine cells quality evaluation based on measurement of hyperfine transition linewidths - the impurities in absorption media cause line broadening of the transitions. Pilot measurement shows that presented method achieves a very good sensitivity to the iodine purity and together with a need of relatively simple setup can be considered as a novel method for absorption cells quality verification.
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Advanced Laser Measuring Systems in Nanometrology
Lazar, Josef ; Hrabina, Jan ; Holá, Miroslava ; Vychodil, M.
We present a development of a nanometrology system combining local probe microscopy and precise positioning and measuring in the nanoscale. The positioning operates in short range with a focus on precision; displacement measurement controls the sample stage in six degrees of freedom with high-resolution interferometry. The system is designed to operate as a national standard for nanometrology. The contribution presents collaborative work with Meopta company.
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Multidimensional interferometric measuremenr system for AFM microscopy - national standard for nanometrology
Hrabina, Jan
We present the design and performance characteristics of 6-axis interferometric measurement system for local probe microscopy. Described measurement tool was developed in colaboration with the Czech Metrological Institute in Brno and it is intended to solve as a national nanometrological standard. The system in based on a commercial nanopositioning sample table controlled by piezoelectric transducers, a metrological frame and a laser interferometric setup for dimensional measurements in six degrees of freedom.
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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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