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Optical coatings for absorption cells
Oulehla, Jindřich ; Hrabina, Jan ; Holá, Miroslava ; Pokorný, Pavel ; Lazar, Josef
One of the key optical components used in laser stabilisation is an absorption cell filled with a gas medium. The optical windows of these cells are antireflection coated to minimise optical losses. During the production process, these coatings are subject to high temperatures and are in direct contact with the gas medium. In some special applications, there might be other factors, such as cosmic radiation, to consider. This contribution deals with the coatings’ resistance to these effects.
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Optical frequency references
Hrabina, Jan
Optical frequency references based on absorption cells represent a traditional and essential tool for frequency locking of precise laser standards. One of the most often used absorption media is a molecular iodine 127I2, which offers a rich atlas of strong and narrow absorption lines across mostly whole visible part of optical spectrum. The main disadvatage of this media can be seen in its high corrosivity and sensitivity to presence of foreign substances. This contribution is oriented to comparison of possible measurement methods for bulk- and also optical fiber- based iodine absorption cells quality and chemical purity testing.\n\n
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SMV-2015-21: Optical frequency reference for visible spectral range
Lazar, Josef ; Hrabina, Jan ; Holá, Miroslava ; Oulehla, Jindřich ; Pokorný, Pavel
The content of this contractual research project for the institute of biophysical chemistry was a research and development of an optical frequency reference for the stabilization of a laser for spectroscopy in the visible spectral range. Spectroscopy measurements with a stabilized laser improve significantly the precision of the measurement thanks to direct traceability of the optical frequency to specific transitions in a suitable absorbing media that are listed in the recommendations of the international metrology commission. The reference is represented by a medium of ultrapure vapour of molecular iodine filed into a cell. The optical design of the cell includes windows with antireflexion coatings and a design with multipass arrangement.
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SMV-2015-24: Optical frequency references for laser spectroscopy
Hrabina, Jan ; Holá, Miroslava ; Oulehla, Jindřich ; Pokorný, Pavel ; Lazar, Josef
The contractual project was oriented to development and research of novel types of absorption cells for laser spectroscopy applications – these cells are intended for frequency stabilization of ultra-stable laser standards and investigation of spectral parameters of unknown liquids and gaseous environments. Novel methods for preparation of antireflection coatings on optical windows were investigated due to strict request for minimalization of optical losses and backreflections of interacting laser light at optical windows of the developed cells. Research of methods for thermal protection of the optical windows during the welding process was oriented to unique approach of inert gas jet cooling of AR coatings. Investigation of possibility of AR coatings homogenization was done by method of thermal baking at different temperature levels.
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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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Měření čistoty jódu v absorpčních kyvetách pro frekvenční stabilizaci laserů
Hrabina, Jan ; Petrů, František ; Jedlička, Petr ; Číp, Ondřej ; Lazar, Josef
In the contribution we present a system for measurement of iodine purity by means excitation of a selected strong transition, measurement of induced fluorescence and evaluation by the Stern-Volmer formula. The arrangement is based on a pumping Ar-ion laser tuned to the transition of interest but its linewidth far exceeds the transition. Frequency noise of the laser is effectivelly reduced by monitoring the fluorescence in a second, reference iodine cell and together with monitoring of the laser power enables cancelation of the frequency noise influence which generates errors by demodulating on the absorption profile. The level of the scattered light is subtracted as well. All the measured data are digitally processed and the experiment is fully computer controlled.
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