Abstract
Zinc gallate (ZnGa
2
O
4
) spinel ceramics doped with Mn
2+
ions was prepared by a solid-state reaction at 1200 °C in air. Manganese concentration was equal to 0.05 mol.% of MnO with respect ...to ZnO. Ceramics produced in this way show an efficient green emission at about 505 nm under UV or X-ray excitations, which is caused by Mn
2+
ions. This green emission is observed also as a relatively long afterglow (visible to the naked eye in the dark for about one hour) after switching-off the X-ray excitation. Time profiles of the beginning of glow and afterglow have been studied together with thermally stimulated (TSL) and optically stimulated (OSL) luminescence. Experimental results demonstrate a presence of few types of shallow and deep traps responsible for the observed afterglow and TSL/OSL emission of the material. The possibility of pulsed optical stimulation and time-resolved OSL characteristics of ZnGa
2
O
4
: Mn
2+
has been reported for the first time. The presented results suggest the ZnGa
2
O
4
: Mn
2+
spinel as a promising material for further fundamental research and possibility of application as a green long-lasting phosphor or storage phosphor for TSL/OSL radiation dosimetry.
Photoluminescence excitation and emission spectra of Mg1-xZnxGa2O4 solid solutions (x = 0; 0.25; 0.5; 0.75; 1.0) co-doped with 0.05mol% Mn2+ and 4mol% Eu3+ ions have been investigated at room ...temperature. Polycrystalline samples were synthesized using high-temperature solid-state reaction technique. XRD measurements confirmed that all ceramic samples are compounds of a spinel structure. Lattice parameter follows linear dependence on composition that confirms Vegard's law for a Mg1-xZnxGa2O4 solid solution system. Complex broad luminescence band ranging from 350 to 475nm ascribed to emission from host defects was found at the excitation in "band-to-band" spectral region. Noticeable intense matrix luminescence in ceramic samples with x = 0.25 and 0.5 was observed. Emission of Mn2+ ions is presented by an intense band with a maximum around 505 nm and shifts at different compositions. Intense excitation of Mn2+ ions was found around the fundamental absorption edge. Complex excitation nature of Mn2+ ions was suggested. The charge transfer band and f-f excitation lines were found in excitation spectra of Eu3+ ions. Luminescence of Eu3+ ions is represented by a number of sharp f-f lines in the 575–650nm spectral region. Composition changing from MgGa2O4 to ZnGa2O4 leads to suppression of Eu3+ ions emission which shows a maximum at x = 0.25. Maximum of matrix luminescence and emission of Mn2+ ions were found at x = 0.50. Further increase of zinc amount in Mg1-xZnxGa2O4 solid solution leads to suppression of intensity of all luminescence bands. The influence of excitation wavelength and composition on the visible range luminescence intensity has been shown. Commission Internationale de l'Eclairage chromaticity diagrams are presented for different compositions and excitation conditions.
Ceramic samples of pure MgGa2O4, MgGa2O4: 0.05 mol.% Mn and MgGa2O4: 0.05 mol.% Mn, 5 mol.% Eu were synthesized via high‐temperature solid state reaction method. X‐ray diffraction measurements ...confirmed formation of spinel structure with Fd3m space group in all investigated samples. Clearly polycrystalline nature of ceramic samples with grain distribution from 1 to 5 μm was confirmed with SEM investigations. An intense broad band that excites in fundamental absorption edge has a maximum around 505 nm and corresponds to emission of Mn2+ ions. A charge transfer band (from O2– to Eu3+) with maximum at about 260 nm was found in the excitation spectra of Mn2+ and Eu3+ co‐doped samples. Luminescence band around 430 nm that corresponds to emission from host defects was found in all investigated samples. Excitation and emission of Eu3+ ions is presented by sharp lines with the most intense at 393 and 617 nm which are associated with 7F0→5L6 and 5D0→7F2 transitions in Eu3+ ions, respectively.
Ceramic samples of pure MgGa
2
O
4
, MgGa
2
O
4
: 0.05 mol.% Mn and MgGa
2
O
4
: 0.05 mol.% Mn, 5 mol.% Eu were synthesized via high‐temperature solid state reaction method. X‐ray diffraction ...measurements confirmed formation of spinel structure with Fd3m space group in all investigated samples. Clearly polycrystalline nature of ceramic samples with grain distribution from 1 to 5 μm was confirmed with SEM investigations. An intense broad band that excites in fundamental absorption edge has a maximum around 505 nm and corresponds to emission of Mn
2+
ions. A charge transfer band (from O
2–
to Eu
3+
) with maximum at about 260 nm was found in the excitation spectra of Mn
2+
and Eu
3+
co‐doped samples. Luminescence band around 430 nm that corresponds to emission from host defects was found in all investigated samples. Excitation and emission of Eu
3+
ions is presented by sharp lines with the most intense at 393 and 617 nm which are associated with
7
F
0
→
5
L
6
and
5
D
0
→
7
F
2
transitions in Eu
3+
ions, respectively.
Ceramic samples of pure MgGa sub(2)O sub(4), MgGa sub(2)O sub(4): 0.05 mol.% Mn and MgGa sub(2)O sub(4): 0.05 mol.% Mn, 5 mol.% Eu were synthesized via high-temperature solid state reaction method. ...X-ray diffraction measurements confirmed formation of spinel structure with Fd3m space group in all investigated samples. Clearly polycrystalline nature of ceramic samples with grain distribution from 1 to 5 mu m was confirmed with SEM investigations. An intense broad band that excites in fundamental absorption edge has a maximum around 505 nm and corresponds to emission of Mn super(2+) ions. A charge transfer band (from O super(2-) to Eu super(3+)) with maximum at about 260 nm was found in the excitation spectra of Mn super(2+) and Eu super(3+) co-doped samples. Luminescence band around 430 nm that corresponds to emission from host defects was found in all investigated samples. Excitation and emission of Eu super(3+) ions is presented by sharp lines with the most intense at 393 and 617 nm which are associated with super(7)F sub(0) arrow right super(5)L sub(6) and super(5)D sub(0) arrow right super(7)F sub(2) transitions in Eu super(3+) ions, respectively.
Zinc gallate compounds codoped with manganese and europium ions were synthesized using the high-temperature solid-state reaction method. All samples were "characterized" by X-ray diffraction ...measurements, ultraviolet reflection spectroscopy, and photoluminescence spectroscopy. Structural investigations confirmed that incorporation of europium ions in zinc gallate host leads to distortion of the spinel unit cell and increase in lattice parameter. Manganese ions show the intense excitation in the region of band-to-band transitions. Zinc gallate spinel compounds codoped with manganese and europium ions exhibit emission in the whole spectral region. Among the manganese and europium activator emissions in the "green" and "red" spectral regions, the "blue" emission of spinel matrix was observed. Photoluminescence excitation spectra of europium ions and reflection spectra show similar results in the near-ultraviolet region of the spectra. The optimal concentration of europium activator was determined. Europium doping level leads to redistribution of excitation and emission intensities of zinc gallate codoped samples. The possible energy transfer mechanisms between matrix, manganese, and europium ions are discussed. Overlapping of excitation bands of all types of luminescence gives a possibility to obtain emission in the whole visible spectral range. The Commission Internationale de l'Eclairage chromaticity diagrams confirmed a possible application of the studied zinc gallate spinel compounds codoped with manganese and europium ions for the development of ultraviolet and near-ultraviolet phosphors with flexible emission color in the visible spectral range.
A user‐friendly, fiber‐coupled, single‐photon source operating at telecom wavelengths is a key component of photonic quantum networks providing long‐haul, ultra‐secure data exchange. To take full ...advantage of quantum‐mechanical data protection and to maximize the transmission rate and distance, a true quantum source providing single photons on demand is highly desirable. This great challenge is tackled by developing a ready‐to‐use semiconductor quantum‐dot‐based device that launches single photons at a wavelength of 1.3 µm directly into a single‐mode optical fiber. In the proposed approach, the quantum dot is deterministically integrated into a nanophotonic structure to ensure efficient on‐chip coupling into a fiber. The whole arrangement is integrated into a 19ʺ compatible housing to enable stand‐alone operation by cooling via a compact Stirling cryocooler. The realized source delivers single photons with a multiphoton events probability as low as 0.15 and a single‐photon emission rate of up to 73 kHz into a standard telecom single‐mode fiber.
A user‐friendly, compact, and portable triggered single‐photon source operating in the telecom O‐band is demonstrated. The device provides single photons with g(2)(0) = 0.15 and a flux of up to 73 kHz at a standard physical‐contact single‐mode fiber connector output. A fully deterministic fabrication technology makes it the first application‐ready quantum‐dot‐based source to enable ultra‐secure data exchange in future fiber‐based quantum communication networks.
Zinc gallate (ZnGa
O
) spinel ceramics doped with Mn
ions was prepared by a solid-state reaction at 1200 °C in air. Manganese concentration was equal to 0.05 mol.% of MnO with respect to ZnO. ...Ceramics produced in this way show an efficient green emission at about 505 nm under UV or X-ray excitations, which is caused by Mn
ions. This green emission is observed also as a relatively long afterglow (visible to the naked eye in the dark for about one hour) after switching-off the X-ray excitation. Time profiles of the beginning of glow and afterglow have been studied together with thermally stimulated (TSL) and optically stimulated (OSL) luminescence. Experimental results demonstrate a presence of few types of shallow and deep traps responsible for the observed afterglow and TSL/OSL emission of the material. The possibility of pulsed optical stimulation and time-resolved OSL characteristics of ZnGa
O
: Mn
has been reported for the first time. The presented results suggest the ZnGa
O
: Mn
spinel as a promising material for further fundamental research and possibility of application as a green long-lasting phosphor or storage phosphor for TSL/OSL radiation dosimetry.
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