Infrared Luminescence of Er[sup 3+] in Calcium Thiogallate

Abstract

Luminescent properties of CaGa 2 S 4 :Er polycrystals in the visible and infrared spectral ranges were investigated. The presence of two different point symmetries for Er 3ϩ centers is well established by selective and polarized photoexcitation. The Ca thiogallate compound can be considered as a promising material for optical communication purposes due to the intense Er 3ϩ infrared luminescence in the 1.55 m range.Erbium-doped materials are of great interest in the thin film integrated optoelectronic technology, due to their Er 3ϩ intra-4f infrared ͑IR͒ emission at 1.55 m, a standard telecommunication wavelength in band C ͑1530 to 1560 nm͒. Dielectric thin films of different Er-doped materials can be used to fabricate planar optical amplifiers or lasers 1-5 that can be integrated with communication systems. In wide bandgap materials, Er 3ϩ ions provide also several emissions in the visible range. The ratio of the visible and IR emission intensities depend on the host material type and erbium concentration. 6 In materials with a small phonon energy the visible luminescence predominates 7 under ultraviolet ͑photoluminescence, PL͒ and electron-beam ͑cathodoluminescence, CL͒ excitations. In oxides, 8 because of the large phonon energy, the multiphonon relaxation of the excited electrons to the lower levels give rise usually to infrared and red emissions.Owing to these considerations, using small phonon energy sulfides is a possibility for practical applications. But these materials must be stable toward hydrolysis and have a high solubility for rare-earth elements.Thiogallates of the different second group elements are convenient for all the reasons mentioned above. 9 CaGa 2 S 4 and SrGa 2 S 4 crystallize in the orthorhombic system with the space group D 2h 24 -Fddd 10 with Ca and Sr ions located in three slightly different sulfur square antiprisms ͑Wyckoff positions: 8a, 8b, and 16e͒. But it has been established that for the strontium thiogallate compound doped with Nd and codoped with Na for charge compensation, there is an ordered distribution of Na ϩ and Nd 3ϩ ions: the Nd 3ϩ ions occupy the a and b polyhedra which have no common apex. 11 Therefore, the interactions responsible for concentration quenching are considerably reduced.CaGa 2 S 4 :Er luminescence properties have been intensively investigated in the visible range up to 700 nm in the past. 9,12,13 The main task of this paper is to analyze the luminescence properties of Er in the IR range and by selective laser spectroscopy and polarization methods to index the emission lines and determine the nature of the corresponding luminescence centers. MeasurementsThis paper describes the results obtained for CaGa 2 S 4 :Er polycrystals prepared by solid-phase synthesis from stoichiometric amounts of calcium ͑CaS: 99.99͒ and gallium (Ga 2 S 3 : 99.95) sulfide powders in a sulfur vapor atmosphere at 1000°C in a vacuum pumped sealed quartz bulb. Activation by Er ͑2 atom %͒ was realized using ErF 3 ͑99.9͒ doping during the synthesis process.The photon excitation at 33...

Термостимулированная люминесценция кристалла Ca(Al-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-)-=SUB=-2-=/SUB=-S-=SUB=-4-=/SUB=-:Eu-=SUP=-2+-=/SUP=-

“…Максимальная энергия фононов и хорошие оптические свойства позволяют получать высокоэффективные люминофоры, а элек-тропроводность бывает пригодна для создания электролюминесцентных дисплеев [2][3][4] [5][6][7][8][9][10]. CaGa 2 S 4 с примесью эрбия дает фотолюминесцен-цию на длине волны 1554 nm, что подходит для применения его в телекоммуникации [11]. Легирование тиогаллата кальция ионами Dy и Nd дает возможность применения этих материалов в лазерах [12,13] Известно, что исследование ТЛ в люминесцентных материалах позволяет определить важнейшие параметры ловушечных уровней (энергия активации, сечения захвата, частотный фактор и др.…”

Low-temperature thermoluminescence in CaGa2S4:Eu2+

“…Maximum phonon energy and good optical transmission properties allows to the realization of high-efficiency phosphors [13,14], whose good electrical conduction properties are also promising for electroluminescent displays [15]. CaGa 2 S 4 doped with erbium exhibits a photoluminescence (PL) emission at 1554 nm, suitable for telecommunication application in the C band [16] doping with Dy and Nd was investigated for laser applications [17,18]. Calcium thiogallate crystallizes in an orthorhombic structure with space group D 2h 24 -Fddd [19] and is characterized by three different crystallographic sites for the calcium ion: two with D 2 point symmetry and one with C 2 .…”

Photoluminescence of Ce and Pr codoped calcium thiogallate

“…Among these materials calcium and strontium thiogallates (CaGa 2 S 4 and SrGa 2 S 4 respectively) activated with cerium, are promising blue-green phosphors, and have been successfully employed for flat panel displays [4,5]. CaGa 2 S 4 doped with trivalent Er exhibits a strong luminescence at 1554 nm with lifetime of 2.7 ms, promising for laser applications in the C-band (1530 -1560 nm) for telecommunication [6]. In addition laser oscillation at 566 nm with a range of tunability of 20 nm, was observed in CaGa 2 S 4 :Eu 2+ [7], while middle infrared laser emission was reported for CaGa 2 S 4 :Dy 3+ [8].…”