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Laser spectroscopy and absorption spectra of HCN
Hošek, Martin ; Hrabina, Jan ; Řeřucha, Šimon ; Pravdová, Lenka ; Lazar, Josef ; Číp, Ondřej
Hydrogen Cyanide (specifically isotope H13C14N) has significant potential as an absorption medium for the frequency stabilised lasers’ realisation because its absorption spectrum covers the whole telecommunication C-band (1530-1565 nm). The broad absorption spectrum can be used not only for calibration of optical telecommunication devices but also for modern interferometric methods that are useful for measuring macroscale objects (e.g., FSI - frequency scanning interferometry). Our research aims to precisely characterise the profile of HCN’s spectral lines and determine the optical frequency of absorption lines’ corresponding centres.
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Silver micro drop structured twice around the earth
Meluzín, Petr ; Tryhuk, V. ; Horáček, Miroslav ; Knápek, Alexandr ; Krátký, Stanislav ; Matějka, Milan ; Kolařík, Vladimír
Planar micro structuring of thin metallic layers allows to achieve required surface properties of metallic layers covering bulk materials. Recently, the arrangement of micro holes or pillars placed around the primary spiral according to a phyllotactic model was presented. This deterministically aperiodic planar arrangement was used for benchmarking purposes of the e-beam writer patterning. This arrangement based on single primary spiral and a variety of derived secondary spirals has several interesting properties. One of them is a very low ratio between the area populated by individual micro elements and the length of the primary phyllotactic spiral. This paper presents analysis of the phyllotactic spiral length and the rising gradient at the spiral outer edge. The practical part of the presented work deals with the patterning of a thin silver layer deposited on the silicon or glass substrates using e-beam pattern generation, lithography techniques and related technologies. An interesting impact of the mentioned spiral properties on the e-beam writing strategies and the exposure ordering strategy are also discussed.
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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.
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Utilization of hydrogen cyanide as an absorption media for laser spectroscopy
Hošek, Martin ; Řeřucha, Šimon ; Pravdová, Lenka ; Čížek, Martin ; Hrabina, Jan ; Číp, Ondřej
The main goal of our investigation is the use of hydrogen cyanide (concretely isotope H13C14N) as absorption medium for realisation of etalon of optical frequency. The advantage of HCN over typically used acetylene (isotopes 13C2H2 and 12C2H2) is the better availability and also the wider absorption spectrum in the 1550 nm wavelength band (telecommunication band). The hyperfine transitions in HCN were investigated in the 90‘, but because of technological limitations the measured data are not as precise as the data for C2H2. We aim on use of more developed methods (saturated absorption spectroscopy, optical frequency lock, beat-note against the optical frequency comb) for the measurement of more precise data of absorption lines of HCN. Our other goals will be to obtain the data enough precise to allow the use of them in Mise en pratique.
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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.
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Hiding e-beam exposure fields by deterministic 2D pattering
Horáček, Miroslav ; Knápek, Alexandr ; Matějka, Milan ; Krátký, Stanislav ; Urbánek, M. ; Mika, Filip ; Kolařík, Vladimír
The high stability and good current homogeneity in the spot of the e-beam writer is crucial to\nthe exposure quality, particularly in the case of large-area structures when gray-scale\nlithography is used. Even though the deflection field distortion is calibrated regularly and\nbeam focus and beam astigmatism is dynamically corrected over the entire deflection field, we can observe disturbances in the exposed relief.\nRecently, we presented a method that makes use of e–beam exposure imperfection by\nintroducing marginally visible high–frequency diffraction gratings of variable pitch that fill in\nseparate orthogonal exposure fields. The actually presented approach follows up our\nresearch on aperiodic arrangements of optical primitives, especially on the phyllotactic–\nlike arrangement of sub–micron relief optical elements. This approach is extended from the\ndiffraction element arrangement to the higher level of exposure fields arrangements.
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Optical binding of polystyrene particles in tractor beam
Damková, Jana ; Chvátal, Lukáš ; Oulehla, Jindřich ; Ježek, Jan ; Brzobohatý, Oto ; Zemánek, Pavel
The motion of a particle illuminated by a laser beam is usually driven by the photon flow due\nto the radiation pressure and therefore for particle trapping, one has to employ gradient forces. But in a tractor beam, objects are illuminated by the uniform light intensity and even so they can be pulled against the beam propagation. There have been developed several techniques how to create such a tractor beam. In our case, the tractor beam is created by two identical Gaussian beams that interfere under the defined angle. It creates the\nstanding wave, where in the transversal plane the particle is trapped by means of the gradient\nforce, but in the total beam propagation direction, the particle manipulation is driven by the non-conservative force. It is remarkable that this force can for the specific combinations of\nparameters pull the micro-particle against the beam propagation. This kind of behavior is\nbecause of the particle scattering where the majority of the incident photons is scattered in the forward direction and, based on the principle of action and reaction, the transfer of\nmomentum leads to a backward movement of the object. The pushing and pulling force is\nsensitive to the polarization of the laser beam, its incident angle and the particle size so this\ntechnique can be used for example for sorting of objects of different sizes.
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Lift-off technology for thick metallic microstructures
Krátký, Stanislav ; Horáček, Miroslav ; Meluzín, Petr ; Kolařík, Vladimír ; Matějka, Milan ; Oulehla, Jindřich ; Pesic, Z.
This paper deals with a method enabling the preparation of thick metallic microstructures on metal substrates. Such metallic microstructures can be used as a resolution samples to characterize various microanalysis techniques, such as X-ray fluorescence (XRF) or X-ray photoelectron spectroscopy (XPS). Moreover, the\npatterned samples could be used as anodes to characterize focusing properties of X-ray tubes for micro CT systems. Considering that the standard lift-off technique is designated for structures with the thickness of several hundred nanometers at most, we had to modify lift-off technique to be possible to use it for preparation of very thick metal layers (several microns) with spatial resolution of a few microns. The mask with the desired pattern for UV exposure was prepared by e-beam lithography. SU-8 photoresist was used for a lift-off because of its aspect ratio ability, process purity and high resistance to heating. We used a thin layer of PMMA under the SU-8 masking layer to guarantee the photoresist would lift-off correctly. Thick aluminum layer was deposited by thermal evaporation. The dependence of metal layer thickness as a function of required exposed\nline width was determined. The final lift-off process was carried out in acetone ultrasonic bath. Generally, this technology can be used for the evaporate deposition of various materials with several microns thick layer in\nmicron resolution.
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Deterministic Aperiodic Image Device
Horáček, Miroslav ; Meluzín, Petr ; Krátký, Stanislav ; Knápek, Alexandr ; Mika, Filip ; Chlumská, Jana ; Matějka, František ; Král, Stanislav ; Brunn, Ondřej ; Giričová, D. ; Kopal, Jaroslav ; Kolařík, Vladimír
The paper deals with the analysis, design and preparation of a diffractive optically variable imaging device consisting of a deterministic aperiodic mesh formed by basic optical elements. The theoretical basis is complemented by numerical analysis and presentation of the implemented master and its replicas.
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Effect of thermal radiation on low temperature measurement for various types of temperature sensor installations
Urban, Pavel ; Hanzelka, Pavel ; Králík, Tomáš ; Vlček, Ivan ; Srnka, Aleš
We investigated an effect of thermal radiation (300 K) on precision of low temperature measurement of a sample holder (or sample) in an UHV SEM/SPM microscope working at range down to 20 K for various ways of temperature sensor mounting. We designed a special copper casing for installation of Lake Shore\ntemperature sensors (CernoxTM and Si diodes) encapsulated in SD packages. The sensor body is attached direct to the casing using indium solder. The current leads pertaining to the sensor are thermally anchored but electrically insulated from the casing. Quality of sensors installation in the casing was tested for various ways of mounting on a cooled plate. Insufficient thermal anchoring of electrical wires and thermal shielding were imitated. Comparative measurement was also performed with sensors in SD package mounted without\ncasing. The experiments proved that our special design of temperature sensors casing is adequate for intended application of temperature measurement of sample holder in UHV SEM/SPM microscope. In contrary, measurement precision of unprotected sensors was absolutely unsuitable.
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