•The luminescence characteristics of GaN films implanted with Erbium at low doses were evaluated.•The temperature dependence of the YL band allowed us to identify the VN as the main responsible ...defect for this emission.•The color coordinates analysis indicates that Er3+/Yb3+ co-doped GaN emits at RT a in the white-light region.•The maximum sensitivity reached was 15×10−4K−1 at 200K.•The significant temperature sensitivity indicates its potential as optical temperature sensor in the range 200–300K.
The luminescence characteristics of GaN films implanted with Er at low doses were evaluated. The defect-related yellow luminescence (YL) and green luminescence (GL) bands observed under direct excitation with 488nm were attributed to the transitions via different charge levels of the same defect. The quenching behavior of the luminescence intensity either with the temperature or concentration variation can be attributed to nonradiative energy transfer (ET) and/or charge transfer by trapping impurities. The temperature dependence of the YL band allowed us to identify the defect responsible for this emission. The best candidate for this defect was found to be a nitrogen-vacancy. A GaN sample co-doped with Er3+ and Yb3+ ions was prepared, and its optical properties were analyzed. The incorporation of Yb3+ improved the PL emission intensity in the visible region. This feature results from the efficient ET processes between these two doping ions. The color coordinate analysis indicates that Er3+/Yb3+ co-doped GaN semiconductor emits light with color in the white-light region. To investigate the temperature sensing application of the synthesized co-doped semiconductor, the temperature-sensing performance was evaluated using the fluorescence intensity ratio technique in the temperature range 200–300K. The significant temperature sensitivity indicates its potential as a temperature sensing probe. The maximum sensitivity was 15×10−4K−1 at 200K.
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In the present work we present a review of the
2
μ
m
laser based on fluoride crystals. We will provide a brief description of the theoretical aspects of rare earth ions embedded in insulating ...crystals, with particular attention to the advantages in using fluoride single crystals and the growth technique. The core article is represented by an overall survey of the laser and spectroscopic properties:
Sections 4 and
6 will present the spectroscopic properties of the Tm,Ho and Tm, respectively, explained in the frame of the rate equation formalism and we will report a summary of the literature results. Finally
Sections 5 and 7 will describe the state-of-the-art for the two systems.
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Nowadays, simple and non-destructive methods able to recognize pathogens in real time and in living tissues are still missing. This study has been designed to evaluate the presence of fungi (i.e. ...Gnomoniopsis spp.) in chestnuts. To this aim, a measurement setup based on terahertz radiation has been used to highlight the presence of fungal diseases in chestnut samples. A population of fifty chestnuts that was known to be partially infected by Gnomoniopsis spp., has been imaged in the low terahertz range by a compact and portable active imaging system equipped with a 100 GHz (0.1 THz) source. The relationship between the chestnut physical parameters, such as mass or volume, and the light attenuation in healthy and infected fruits has been tentatively explained by assuming a different water density and a different physical structure in healthy and unhealthy fruits, due to carbohydrates hydrolysis by the fungi. The preliminary results here described suggest that the sole analysis of the light attenuation combined with the measurement of weight or volume of a chestnut can provide an immediate indication of the presence of fungi in the fruits.
•Non-destructive imaging approaches able to recognize pathogens in real time in living tissue are still not available.•Fifty chestnuts, part of them infected by Gnomoniopsis spp., have been investigated using a THz spectroscopic approach.•Results suggest that our method can provide a fast confirmation of the presence of fungi in the chestnuts investigated.
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Among the non-destructive techniques capable of obtaining information on biological systems even in vivo, terahertz-based techniques are emerging due to their specificity to the water content, which ...can represent an important indicator of the presence of microorganisms and, in general, of the health status, particularly in plants. Nevertheless, the analysis of the extracted data (especially for images) and the exploitation of the potential of the technique for the study of the complex phenomena that occur in living tissues are still almost unexplored fields. In this work, the hydration status of leaves both in vivo and ex vivo was monitored continuously and non-destructively by acquiring videos in the sub-terahertz range through a portable imaging system. A model for describing the water flow in space and time in the midvein of a leaf is obtained which is suitable for the analysis of the data extracted from the portable sub-terahertz imaging system. These results show that terahertz-based technology can be used to study biological phenomena even in vivo; moreover, they pave the way for the introduction of a general method for the analysis of terahertz data based on surface fits in space and in time as well.
•THz radiation is effective in monitoring the water distribution in living tissues.•Leaf water distribution gives information about its health status.•Analysis of THz video data monitors hydration and dehydration dynamics of leaves.•Space and time water diffusion in leaves can be analysed simultaneously.
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This work is devoted to the study of BaY2F8 crystal, doped with different concentrations of trivalent praseodymium ion in the range from 0.3% to 3%. Spectroscopic properties of these materials showed ...a large dependence on two parameters: dopant concentration and temperature. Judd–Ofelt model analysis of absorption and emission spectra revealed the potential of our materials as promising blue laser emitters.
•At high concentration, quenching effect appears on emission.•The temperature variation revealed attenuation of emission intensity.•The spectroscopic parameters were determined by JO theory.
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The Italian institute for nuclear physics (INFN) has financed the SIMP project (2019–2021) in order to strengthen its skills and technologies in the field of meV detectors with the ultimate aim of ...developing a single microwave photon detector. This goal will be pursued by improving the sensitivity and the dark-count rate of two types of photodetectors: current-biased Josephson junction (CBJJ) for the frequency range 10–50 GHz and transition-edge sensor (TES) for the frequency range 30–100 GHz. Preliminary results on materials and devices characterization are presented.
The development of terahertz based technology has given the opportunity for the realization of non destructive techniques capable of gaining meaningful information on delicate systems such as ...biological samples. Here, the health status of leaves in vivo has been monitored through a portable terahertz imaging system. The data have been extracted and analysed from the images acquired and compared with analogous results reported in the literature on similar systems. The possibilty of extracting additional information from the images regarding leaf details has also been explored.
We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting ...Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF(4) and Pr:BaY(2)F(8) was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB(3)O(5) as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF(4) and Pr:BaY(2)F(8), respectively.
Josephson junctions, in appropriate configurations, can be excellent candidates for detection of single photons in the microwave frequency band. Such possibility has been recently addressed in the ...framework of galactic axion detection. Here are reported recent developments in the modelling and simulation of dynamic behaviour of a Josephson junction single microwave photon detector. For a Josephson junction to be enough sensitive, small critical currents and operating temperatures of the order of ten of mK are necessary. Thermal and quantum tunnelling out of the zero-voltage state can also mask the detection process. Axion detection would require dark count rates in the order of 0.001 Hz. It is, therefore, is of paramount importance to identify proper device fabrication parameters and junction operation point.
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