National Repository of Grey Literature 83 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Estimation of mechanical parameters of thin films using finite element analysis
Tinoco Navaro, Hector Andres ; Holzer, Jakub ; Pikálek, Tomáš ; Buchta, Zdeněk ; Lazar, Josef ; Chlupová, Alice ; Kruml, Tomáš ; Hutař, Pavel
This study shows a methodology to estimate mechanical parameters of thin films by means of a bulge\ntest and a numerical approach. The methodology is based on the combination of finite element analysis with a\nclassical analytical method. Finite element modelling was conducted for monolayer (Si3N4) membranes of 2x2mm\nwith the aim to approximate both the load-deflection curves experimentally measured and the classical loaddeflection\nanalytical model. Error functions were constructed and minimized to delimit a coupled solution space\nbetween Young’s modulus and Poison’s ratio. In a traditional bulge test analysis only one of the elastic properties\ncan be determined due to that there is not unique solution in the estimations of these parameters. However, both\nelastic parameters were determined through the proposed numerical procedure which compares the deformed\nsurfaces for a specific set of optimal elastic parameters computed. Results shows that the estimated elastic\nproperties agree with corresponding values determined by other methods in the literature
Interferometric System for Length Calibration on a Metre Scale
Jedlička, Petr ; Mikel, Břetislav ; Řeřucha, Šimon ; Matěj, Z. ; Herman, O. ; Holá, Miroslava ; Jelínek, Michal ; Pavelka, Jan ; Číp, Ondřej ; Lazar, Josef
Interferometric system is designed to calibrate the measurement frame, used for periodic assessment of the inner geometry of the reactor active zone chassis. Calibration lenght is up to 3300mm.
Comparison of frequency stability of laser wavelength standards over photonic networks
Pravdová, Lenka ; Hrabina, Jan ; Čížek, Martin ; Lazar, Josef ; Číp, Ondřej
In our work we present a metrological ampaign in which the stability of the 1540 nm normal laser located at the CESNET workplace in Prague was compared with the wavelength of the supercoherent laser transmitted from the ÚPT workplace in Brno via the 306 km phase-coherent transfer line Brno - Prague. The assembled acetylene standard was transferred to the CESNET workplace and a unit receiving coherent wave from the supercoherent laser stabilized by the optical frequency comb and the H-maser at the ISI workplace in Brno was put into operation. The optical frequency mixer with a photodetector recorded a frequency response between the acetylene optical frequency normal and the supercoherent laser distributed over the photonic network whose stability is given by the H-maser in the 15th order. We have verified that the laser normal meets the requirements of the BIMP Recommendation for the Practical Implementation of the Meter Standard.
Stable optical frequency transfer between ISI and CESNET workplaces
Čížek, Martin ; Pravdová, Lenka ; Hucl, Václav ; Jelínek, Michal ; Hrabina, Jan ; Řeřucha, Šimon ; Mikel, Břetislav ; Lazar, Josef ; Číp, Ondřej ; Smotlacha, V. ; Havliš, O. ; Vojtěch, J.
The contribution reports on the current state of a 306km long experimental line for transfering stable optical frequency from a telecommunication band laser standard between ISI CAS (Brno) and CESNET (Prague). The bidirectional link uses a telecommunication fiber with a dedicated DWDM window of 1540-1546 nm.1540-1546 nm. In the Czech rep. this technology can be utilized currently in two fields: remote comparisons of optical frequency standards and remote callibration of instruments (optical spectral analyzers) in industrial applications that do not allow transporting the device to a specialized laboratory. The stability of the optical frequency transfer was evaluated. A long-term measurement of transport delay was conducted. \n
Grazing incidence interferometer for form measurement of hollow cylinders
Šarbort, Martin ; Řeřucha, Šimon ; Holá, Miroslava ; Lazar, Josef
Optical metrology of cylindrical specimens represents an interesting task in scientific and\nindustrial practice. The most precise measurement methods use principles of laser\ninterferometry where the phase difference between the reference wave and the object wave reflected from the tested surface is detected. The form measurement of hollow cylindrical tubes can be advantageously realized by an object wave with conical wavefronts generated by an axicon lens or an equivalent diffractive optical element. An axicon characterized by large apex angle forms a conical wave that fulfills the conditions of the grazing incidence, which results in suppression of the speckle noise. The previous experimental setups were relatively complex since they involved a pair of mutually reversed axicons or a pair of diffractive optical elements that transform the object wave from planar to conical and vice\nversa.
Development of the bulge test equipment for measuring mechanical properties of thin films
Holzer, Jakub ; Pikálek, Tomáš ; Buchta, Zdeněk ; Lazar, Josef ; Tinoco, H.A. ; Chlupová, Alice ; Kruml, Tomáš
The bulge test apparatus designed for the measurement of mechanical material properties of thin films was constructed and tested. The principle of the test is to apply pressure on a free-standing membrane, to measure the membrane shape and to analyse the results. Commercially available silicon nitride (Si3N4) thin films were used for the testing. It is shown that interferometric set-up designed and assembled for the apparatus enables precise determination of 3D shape of the whole membrane, which allows more precise determination of materials parameters compared to measurement of the height of the center of the membrane only. Fit of an analytical formula gives values of Young modulus and residual stress with very good agreement with the literature data. Moreover, FEM model of the bulged membrane was developed. The main aim of the effort is to enable measurement of plastic properties of a thin film of interest, that will be deposited on the Si3N4 membrane with known properties and bulge test will be performed on the bilayer specimen. Subsequently, the material properties of the thin film will be obtained using FEM analysis.
Detecting plasticity in al thin films by means of bulge test
Holzer, Jakub ; Pikálek, Tomáš ; Buchta, Zdeněk ; Lazar, Josef ; Tinoco, H.A. ; Chlupová, Alice ; Náhlík, Luboš ; Sobota, Jaroslav ; Fořt, Tomáš ; Kruml, Tomáš
The Bulge test proved to be a useful tool for measuring elastic properties of thin films and\nfree standing membranes, particularly Young’s modulus and residual stress. The basic principle\nof bulge test is application of differential pressure on one side of the a membrane, measurement of\nthe shape of bulged surface as a function of pressure, in this case via laser interferometer, and\nevaluation of a pressure-deflection relationship. In this study, bilayer membrane consisting of a\nsilicon nitride supporting layer and an aluminium layer deposited by means of magnetron\nsputtering is subjected to the bulge test. The results clearly show signs of a non-linear behavior\nthat is caused by plastic deformation in the aluminium layer. Finite element analysis is being\ndeveloped to describe this behavior because analytical model using deflection of central point and\npressure relation falls apart in case of non-linearity.
Interferometrical system for bulge test thin film characterization
Pikálek, Tomáš ; Holzer, Jakub ; Tinoco, H.A. ; Buchta, Zdeněk ; Lazar, Josef ; Chlupová, Alice ; Náhlík, Luboš ; Sobota, Jaroslav ; Fořt, Tomáš ; Kruml, Tomáš
Behavior of thin film materials undergoing stress and deformation differs from bulk materials. A common method for the mechanical characterization of thin films is nanoindentation based on indenting a small tip into the material. A different approach is a bulge test technique. In this method, a differential pressure is applied on a free-standing membrane and the mechanical properties (Young’s modulus and residual stress) are calculated from the shape of the bulged membrane. In our experiments, we developed an interferometrical system for the membrane shape measurement during the bulge test.
Stabilized laser for spectroscopy on trapped calcium ions
Čížek, Martin ; Pham, Minh Tuan ; Lešundák, Adam ; Hucl, Václav ; Řeřucha, Šimon ; Hrabina, Jan ; Lazar, Josef ; Číp, Ondřej
The paper focuses on the ongoing development of clock laser assembly operating at a wavelength of 729 nm, which will be used for 40Ca+ calcium spectroscopy. As a primary source of coherent radiation, a diode laser with an external resonator operating at a wavelength of 729 nm is used. The width of the spectral line of the free-running laser is approx. 300 kHz. The laser is tunable by a piezoelectric actuator in the range of 10 GHz with a maximum bandwidth of 2 kHz. Fast fine-tuning in hundreds of MHz is possible by modulating the pump current of the laser diode with 50MHz bandwidth. The optical frequency of the laser is locked by means of electronic control loops on a resonator with a finesse better than 300 000 with a mode spectral width of approx. 8 kHz. The cavity of the resonator is made of ULE material and placed in a thermally stabilized vacuum chamber. The entire optical assembly is mounted on an active anti-vibration pad in a wooden box plated with acoustic and thermal isolation. The tuning of the primary laser to the resonator mode is detected by the Pound-Drever-Hall technique.
Trapping and cooling of single ions for frequency metrology and quantum optics experiments
Slodička, L. ; Pham, Minh Tuan ; Lešundák, Adam ; Hucl, Václav ; Čížek, Martin ; Hrabina, Jan ; Řeřucha, Šimon ; Lazar, Josef ; Obšil, P. ; Filip, R. ; Číp, Ondřej
Single trapped ions trapped in Paul traps correspond to ideal candidates for realization of extremely accurate optical atomic clocks and practical studies of the light–atom interactions and nonlinear mechanical dynamics. These systems benefit from both, the superb isolation of the ion from surrounding environment and excellent control of its external and internal\ndegrees of freedom, at the same time, which makes them exquisite platforms for experimental studies and applications of light matter interaction at its most fundamental level. The exceptional degree of control of single or few ion's state enabled in past decade number of major advancements in the applications from the fields of experimental quantum information\nprocessing and frequency metrology, including recent realization of scalable Shor's\nalgorithm, fractional uncertainties of the frequency measurements close to 10-18 level, or simulations of complex quantum many-body effects. These results, together with the rapid advancements in the production of low-noise segmented micro-traps, promise prompt access to long-desired regimes of quantum optomechanics and further development and applications\nof optical atomic clocks.

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2 Lazar, Jan
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