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Optical cavity for ultra-narrow linewidth laser system
Pravdová, Lenka ; Hrabina, Jan ; Čížek, Martin ; Číp, Ondřej ; Procháska, František ; Beneš, Jiří
We designed an optical resonator cavity for narrowing standard commercial laser to sub-Hz linewidth. The optical Fabry Perot resonator is designed hemispherical with all components from ULE material and zero crossing temperature at 33°C. The support Zerodur shelf is isolated from the resonator by two Viton O-rings. The resonator is located in an Aluminium chamber with direct temperature stabilization. 2nd temperature stabilisation is provided by 4 Peltier modules enabling heat exchange between the copper jacket and the assembly surroundings. The stainless-steel jacket has passive isolation and protective function.
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Measurement of magnetic field stability using 40Ca+ ion
Pham, Minh Tuan ; Lešundák, Adam ; Čížek, Martin ; Podhora, L. ; Řeřucha, Šimon ; Jedlička, Petr ; Slodička, L. ; Lazar, Josef ; Číp, Ondřej
One of the main limitations in the long-term measurement of the clock transition's absolute frequency is the magnetic field's fluctuation. The time-varying fluctuation of the external magnetic field leads to frequency shifts of the Zeeman components, thereby reducing the optical clock's frequency stability over time. Currently, optical atomic references are usually implemented with the help of a single ion. However, scaling the number of ions to higher values brings an indisputable benefit in the form of a high signal-to-noise ratio and, thus to the efficiency of the entire measurement process. In this case, the ions are spread over a large area, forming so-called ionic Coulomb crystals. In addition to the spatial stability of the magnetic field, the homogeneity of the magnetic field is also significant when working with Coulomb crystals. Excessive magnetic perturbation can be greatly reduced by covering the assembly with a magnetic shield or by using permanent magnets instead of conventionally used magnetic coils. Another method is averaging over multiple-level transitions. This contribution presents a simple method for measuring the stability of the magnetic field at the ion position.
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Optical fibre dosimeter
Jelínek, Michal ; Mikel, Břetislav
In the nuclear facility, there is currently a demand for optical methods of measuring gamma radiation. For these measurements, we need very robust measurement methods and sophisticated equipment. Silica optical fibres coupled to crystal scintillators are suitable and we present results from their implementation. The scintillators detect gamma radiation and the silica optical fibres transmit the scintillation light from the scintillator to the detector. We used commercially available silica optical fibres up to 1.5 mm in diameter with different numerical apertures to transmit visible light from the scintillators to the detector.
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System for scanning hydrogen cyanide absorption lines
Hošek, Martin ; Řeřucha, Šimon ; Hrabina, Jan ; Čížek, Martin ; Pravdová, Lenka ; Číp, Ondřej
The definition of both meter and second relies on precisely measured frequency. The convenient sources of such frequencies are lasers stabilized by molecular vapours. The He-Ne lasers stabilized by iodin vapours represent the cornerstone sources in the visible spectrum. On the other hand, the infrared spectrum (particularly the 1550 nm C-band) is of metrological interest thanks to its cost-effective, readily available components. The widely used absorption media at 1550 nm has been two acetylene isotopes (12C2H2, 13C2H2), while H13C14N represents an alternative covering a wider spectrum well corresponding to the telecommunication C-band. The 2ν3 rotational-vibrational band had been investigated, but due to the use of not-so-precise methods, the presented data feature high uncertainty compared to acetylene data. We represent methods that will lead to precise assessments of hydrogen cyanide's absorption line centres with the potential to introduce HCN to Mise en Pratique, making it an internationally recognized source of precise frequency for the realization of traceable laser etalons.
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Multiband fiber polygon for accurate time and coherent frequency transmission
Havliš, O. ; Vojtěch, J. ; Šlapák, M. ; Číp, Ondřej ; Čížek, Martin ; Hrabina, Jan ; Pravdová, Lenka ; Slodička, L.
The CESNET association, in cooperation with the Institute of Scientific Instruments of the Academy of Sciences of the Czech Republic (Institute of Scientific Instruments of the CAS, abbreviated ISI CAS), ČD Telematika and University Palacký in Olomouc (UPOL) Department of Optics built a multiband polygon on real optical routes . The multiband polygon is designed for two-way transmission of ultra-stable quantities, i.e. transmission of acurrate time and coherent frequency (T/F).
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Processing of glass by ultrashort pulses
Novotný, Jan ; Mrňa, Libor ; Horník, Petr ; Šebestová, Hana
Use of ultrafast laser pulses for processing of glass materials is promising method for cutting, drilling and manufacturing of free form shapes. No material damage is observed due to nearly zero heat affected zone. Cutting of opticaly coated substrates withou damage to the layers is also possible. Thanks to precision beam positioning system it is possible to manufacture free form shapes for optical (microelents) or microfluidic use. Optical element's surfaces are finished to desired quality by other technologies.
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Stabilization for optical receiver
Kolka, Z. ; Barcík, P. ; Novotný, Jan ; Biolková, V.
Free-Space Optics (FSO) is a wireless optical technology for line-of-sight communications. The front of the receiving optical fiber is located at the focus of the telescope. The relatively small diameter of the core puts extreme demands on receiver pointing under atmospheric turbulences and mounting bracket vibrations. To ensure stability, the beam is stabilized by a fine positioning system. A detection unit evaluates the position of the centre of the laser spot using photodiodes and compensates for deviations by changing the mirror angle.
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