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Frequency references and dissemination
Hrabina, Jan ; Pravdová, Lenka ; Šarbort, Martin ; Čížek, Martin ; Holá, Miroslava ; Oulehla, Jindřich ; Pokorný, Pavel ; Lazar, Josef ; Číp, Ondřej
The work deals with an overview of research topics of the “Frequency references and dissemination” group, Department of Coherence Optics, Institute of Scientific Instruments, Czech Academy of Sciences. These topics include frequency locking of lasers by laser spectroscopy and high-finnese optical cavities, digital holography and optical frequency tranfers through fiber and free-space optical links.
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Highly-coherent laser for precise optical frequencies dissemination
Pravdová, Lenka ; Čížek, Martin ; Hrabina, Jan ; Jelínek, Michal ; Řeřucha, Šimon ; Mikel, Břetislav ; Lazar, Josef ; Havliš, O. ; Altmannová, L. ; Smotlacha, V. ; Vojtěch, J. ; Velc, R. ; Číp, Ondřej
The paper presents a multipurpose laser with a very narrow spectral line, operating at a wavelength of 1540 nm and designed for cooled ions spectroscopy and the dissemination of precise optical frequencies over optical fibre links. The optical frequency of a commercial single-mode laser (NKT Photonics Koheras Basik) is spectrally narrowed to the level of several Hz using a high-quality optical resonator as an optical reference and an acousto-optic modulator as an active control element. The optical resonator is made of a low length thermal expansion coefficient material and is placed in a multi-shell vacuum chamber providing a stable operating environment. Optical frequency stabilisation uses PDH (Pound-Drewer-Hall) modulation and detection technique.
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Free-space optical link fro coherent transfer
Hrabina, Jan ; Čížek, Martin ; Barcík, P. ; Kolka, Z. ; Skryja, P. ; Wilfert, O.
The dissemination of precise optical frequencies and time has an irreplaceable role in many applications (scientific experiments in time and frequency metrology, security of critical infrastructures, synchronisation of navigation systems, sensors). We must deploy a different transmission type where optical fibre links cannot be used. The paper describes the possible distribution of stable optical frequencies by the free-space optical link between FEEC BUT Brno (responsible for development and operation of FSO units) and ISI CAS CR (responsible for optical laser source, optical fibre links, data processing).
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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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SMV-2014-27: Optical system for generation of stable optical frequency
Hrabina, Jan ; Číp, Ondřej ; Čížek, Martin ; Hucl, Václav
The work was oriented to design and development of a stable optical frequency laser standard based on ultra-low noise DFB laser. The laser frequency was locked to selected rotational-vibrational transition of isotopic acetylene gas by the method of linear absorption spectroscopy. The research included: design, investigation and development of narrow-linewidth DFB laser source including of development of ultra-low noise power-supply and control electronics; development of an optical setup equipped with opto-fiber output for automatic locking of the laser to selected transition of the ultra-pure acetylene gas, special custom-design absorption cell development, filled with isotopic acetylene, with optical windows equipped with custom-design antireflection coatings; development of control electronics for automatic searching of absorption lines and automatic locking of the laser frequency to this transition; development of control software.
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