Uncooled MWIR and LWIR photodetectors in Poland

The history, status, and recent progress in the middle and long wavelength Hg_1−xCd_xTe infrared detectors operating at near room temperatures are reviewed. Thermal generation of charge carriers in narrow gap semiconductor is a major limitation or sensitivity. Cooling is a straightforward way to suppress thermal generation of charge carriers and reduce related noise. However, at the same time, cooling requirements make infrared systems bulky, heavy, and inconvenient in use. A number of concepts to improve performance of photodetectors operating at near room temperatures have been proposed and implemented. Recent considerations of the fundamental detector mechanisms suggest that near perfect detection can be achieved without the need for cryogenic cooling. This paper, to a large degree, is based on the research, development, and commercialization of uncooled HgCdTe detectors in Poland. The devices have been based on 3D-variable band gap and doping level structures that integrate optical, detection and electric functions in a monolithic chip. The device architecture is optimized for the best compromise between requirements of high quantum efficiency, efficient and fast collection of photogenerated charge carriers, minimized thermal generation, reduced parasitic impedances, wide linear range, wide acceptance angles and other device features. Recent refinements in the devices design and technology have lead to sensitivities close to the background radiation noise limit, extension of useful spectral range to > 16 μm wavelength and picosecond range response times. The devices have found numerous applications in various optoelectronic systems. Among them there are fast scan FTIR spectrometers developed under MEMFIS project.     

Insight into precursor kinetics using an infrared gas analyser

Precursor kinetics and its influence on MOCVD growth was investigated using an infrared absorption gas analyser. After several refinements, the analyser was able to be used to measure time dependent concentrations of precursors in the growth zone. Changes were induced by periodic switching of corresponding bubbler valves. It was proved that precursor transport could be accurately described by the combined plug flow and perfectly mixed tank model. The studies of the precursor trans-port are strategically important for the growth of multilayer structures, when growth time of particular layers becomes comparable to delays and time constants. One example is quantum wells or interdiffused multilayer process (IMP) used in the growth of Hg1-xCdxTe heterostructures, where knowledge of precursor transport characteristics is vital for understanding and properly designing that growth. The model parameters, sc. the delays and time constants for DIPTe and DMCd, were evaluated for various growth conditions and then successfully used to optimise the growth of complex Hg_1−xCd_xTe heterostructures.     

Optical sensing of parameters crucial for Japanese woodblock print making

Traditional Japanese woodblock printing is a centuries old art form. This time-honoured form of art is at risk of extinction as a consequence of the increasing lack of availability of wild cherry trees, which are a traditionally used woodblock material. Solutions for this material problem have been investigated for several years, but none of the tested materials has been sufficient when compared with the watercolour print quality imprinted by wild cherry woodblocks. To contribute to overcoming this material problem, we have investigated the physical properties of heat-treated woodblock materials made from different wood species. The International Commission on Illumination (CIE) tristimulus values, the CIELAB coordinates, the total reflectance, and the gloss, as well as, the water contact angle from the woodblock surface is observed to have a strong relation to the surface treatment of a woodblock. The surface treatment of a woodblock, in turn, relates to its water delivery, which is the basis for watercolour printing.     

The influence of electron–phonon interaction on the OSL decay curve shape

The significance of the electron–phonon interaction for optically stimulated luminescence (OSL) process in quartz is demonstrated. OSL variation with temperature has been investigated for four samples of natural quartz. Changes of the OSL decay rate have been observed for all components of the OSL signal. The scale and tendency of these changes are comparable with outcomes of computer simulations carried out for the model composed of two deep electron traps, one shallow trap and one recombination centre, taking into account the electron–phonon interactions.     

Dose response of hydrazine – Deproteinated tooth enamel under blue light stimulation

The beta dose response and Optically Stimulated Luminescence (OSL) signal stability characteristics of human tooth enamel deproteinated by hydrazine reagent under blue photon stimulation are reported. Removal of the protein organic component of tooth enamel resulted in a higher OSL sensitivity and slower fading of OSL signals. The effect of chemical sample preparation on the enamel sample sensitivity is discussed and further steps to make this deproteinization treatment suitable for in vitro dose reconstruction studies are suggested.     

Amorphous track models: A numerical comparison study

We present an open-source code library for amorphous track modelling which is suppose to faciliate the application and numerical comparability as well as serve as a frame-work for the implementation of new models. We show an example of using the library indicating the choice of submodels has a significant impact on the modelling outcome.     

Garvey-Kelson relations for nuclear charge radii

The Garvey-Kelson relations (GKRs) are algebraic expressions originally developed to predict nuclear masses. In this paper we show that the GKRs provide a fruitful framework for the prediction of other physical observables that also display a slowly varying dynamics. Based on this concept, we extend the GKRs to the study of nuclear charge radii. The GKRs are tested on 455 out of the approximately 800 nuclei whose charge radius is experimentally known. We find a rms deviation of 0.01fm between the GK predictions and the experimental values. Predictions are provided for 116 nuclei whose charge radius is presently unknown.     

Distinct magnetic properties of one novel type of nanoscale cobalt-iron Prussian blue analogues synthesized in microemulsion

One novel type of nanoscale cobalt-iron Prussian blue analogues (PBA) in the form of mixed nanorods and nanocubes were synthesized using cetyltrimethyl ammonium bromide (CTAB) as the surfactant in microemulsion at low temperature. The generated products were characterized by SQUID, XRD and IR techniques, etc. The effects of potassium contents, cobalt-to-iron ratios, reaction temperatures on the properties of the nanoscale cobalt-iron PBA were systematically explored. The results showed that the novel type of nanomaterials possessed distinct magnetic properties in that their coercivities were intensely dependent on cobalt-to-iron ratios and potassium contents. Furthermore, it was observed that low reaction temperature not only affected the morphologies of the products, but also had influence on their magnetic properties. Additionally, the cobalt-iron Prussian blue analogues were strongly influenced by CTAB around their surface, which led to higher Curie temperatures.     

Optical results of the black hole microquasar SS 433

We present optical spectroscopic observations of SS 433 during different precessional and orbital phases. Our 2004, 2007 and 2008 data provide us a good chance to study the variability of the Hα line at different orbital phases for nearly the same disk inclination. The data show that the Hα of SS 433 usually had a symmetric profile between orbital phases 0.25–0.75, while an asymmetric structure with a strong red peak was observed for other orbital phases. We suggest that the orbital variability of Hα emission is connected with accretion flow from the donor star to the accretion disk. In addition, we attribute the dramatic increase of Hα emission during our 2007 observational run, which had a time scale of one day, to the emergence of strong jets.