A wide range of rare earth doped crystals used as a lasing media includes: Y3Al5O12 (YAG); Al2O3 (sapphire); chalcogenides of ZnS, ZnSe; sesquioxides of Y2O3, Sc2O3 and others.
Ternary thiogallate compounds with common formula AIIB23C46 (where A is: Ca, Sr, Ba; B is: Ga, Al; C is- S, Se, Te) consider as a perspective class of chalcogenide semiconductors revealing bright luminescence and laser oscillation properties when doped with rare-earth elements (Eu2+, Nd3+ , Ce3+ etc).
In the present research, optical properties and observed laser oscillation of transparent ternary chalcogenide crystals of CaGa2S4 and CaGa2Se4 grown by the chemical vapor transport reaction and doped with Eu2+ (1.0-5.0 a t%) are described. The first observation of laser oscillation from a single crystal CaGa2S4 : Eu2+ (1.0-5.0 at%) have been reported earlier, and for CaGa2Se4 : Eu2+ it is reported for the first time in the present article. The life time of the excited state 4f65d of Eu2+ ions in both crystals determined from the luminescence decay kinetics was ~3.8 μsec.
It is shown that photoluminescence maximum in both crystals CaGa2S4 : Eu2+ and CaGa2Se4 : Eu2+ is due to the intra shell transition 4f65d – 4f7(8S7/2) ions.
GaSe-type crystals have attracted increasing attention because of pronounced structural anisotropy, unique optical and Nonlinear Optical Properties, which may lead to numerous applications in light generation (second harmonics and tuning in a wide transparency range of λ= 1÷20 μm) and optoelectronics (radiation detectors, photovoltaic energy converters, photo-resistors, light modulators etc.). In the present work, damage threshold of the Bridgman grown GaSe and its structural analogs ((GaSe1-x Sx (where 0 ≤x ≤0.25, InSe and GaTe)), have been investigated under IR τ = 5 ns pulses (λ= 1.064 μm) of "QUANTELL Brilliant b" laser (pulse energy ~ 850 mJ, f = 20 Hz). For all studied crystals occurrence of local micro defects and pulse induced heating were identified to be responsible for damage threshold mechanism. Results for GaSe obtained in the present work are in good agreement with published in literature for damage threshold excited with laser lines in the spectral range of λ= 1.1 ÷ 2.9 μm lines of the Optical Parametric Generator. The values of damage threshold for solid solutions of GaSe1-x Sx, InSe and GaTe crystals are reported for the first time.
Laser-induced fluorescence KA-14 LIDAR, developed and employed at the National Aviation Academy of Azerbaijan was used for detection of emission spectra of oil spills on the surface of the Caspian sea and earth surface of the Absheron peninsula. It is known, that oil spills may take place due to leakage of oil from different Oil-Gas-Production Companies and Joint Ventures of the State Oil Company of Azerbaijan Republic. There are 8 Oil-Gas-Production Companies and 4 Joint Ventures in Azerbaijan Republic. Fluorescence spectra were excited by 355 nm line of CFR 200- type laser (QUANTEL) with parameters: diameter of laser beam spot- &diameter; = 5 mm (after collimation- 40 mm); frequency of excitation- f = 20 Hz; pulse duration and power of laser- τ= 7 ns and 60 mJ, respectively. Analysis of differences of the spectral positions of maximums of fluorescence spectra, forms of the emissions spectra, as well as peculiarities of fine structures in emission spectra allowed with a high degree of availability to determine from which Oil-Gas-Production Company of State Oil Company of Azerbaijan Republic (including OGPC “Neftjanije Kamni”) leakage took place on the surface of the Caspian sea and on the earth of Absheron peninsula. Results obtained allow, for the first time, to create a data bank of fluorescence spectra of crude oil extracted on the earth of the Absheron peninsula of Azerbaijan as well as from adjacent water areas of the Caspian sea, including OGPC "Neftjanije Kamni."
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