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Lasery s tenkými InAs vrstvami v GaAs - absorpce a elektroluminiscence
Mačkal, Adam
Contribution presents the electroluminescence, photoabsorption and polarization properties of semiconductor lasers with thin strained InAs layers in GaAs at elevated temperature (above 25.sup.o./sup.C). The lasers exhibit high optical recombination efficiency, low threshold current density and wide temperature operation range
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Využití opticky zachycené sondy pro studium velmi slabých interakcí na molekulární úrovni - přehled
Zemánek, Pavel ; Jonáš, Alexandr
A micron-sized dielectric particle confined in a laser trap can be employed as a probe for the measurement of forces in the range from piconewtons to hundreds of piconewtons. Thus, if a biological system of interest (e.g. DNA molecule, single myosin or kinesin molecule, cell membrane) is attached to such a probe, its mechanical and dynamical properties (elasticity, viscosity, forces associated with movement) can be studied during its interaction with the environment with unprecedented resolution. This article introduces the basic principles of the laser trapping and force measurement and illustrates on several examples the great potential of the light-based force transducer for exploiting non-invasively the dynamics of molecular systems
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Emisivita a absorptivita tepelného záření povrchů konstrukčních kovů za velmi nízkých teplot
Musilová, Věra ; Hanzelka, Pavel ; Králík, Tomáš ; Srnka, Aleš
Comparison of thermal radiation properties of surfaces of several metals commonly used in cryogenics is presented. We have measured heat absorbed by a surface of Cu, Al and stainless steel kept at a temperature of about 5 K - 10 K. The source of heat was a parallel black surface placed in a small distance from a tested sample. As a result of our measurement, the dependences of absorptivity on the temperature of the heat radiation source are plotted between 30 K and 140 K. The influence of different types of metal treatment, e.g. chemical and mechanical surface finish and annealing, on radiation heat transfer is presented
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Zařízení pro měření tepelné emisivity při nízkých teplotách
Králík, Tomáš ; Hanzelka, Pavel ; Musilová, Věra ; Srnka, Aleš
In the described device, the thermal emissivity or absorptivity of the sample is measured by substitution of the radiative heat flow between two parallel surfaces by thermal output of a heater. Fast measurements of the mutual emissivity for the range of the temperature of the radiating surface 25 K - 150 K are possible. The absorbing surface has a temperature between 5 K and 10 K when LHe is used as cryoliquid. The desired measurement sensitivity is 1 mK for temperature and 0.1 mikroW for heat power, respectively. The diameter of the whole device is 50 mm and so it is possible to use a commercial Dewar can for the cooling. The form of the sample is a circular plate 40 mm in diameter and 1 mm in thickness with one tested side. The emissivity and its temperature dependence for various surface treatments can be checked immediately before application in a cryogenic system
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