Jiri Oswald

Synthesis and physical properties of the system (GeS2)80−x(Ga2S3)20:xPr glasses

Abstract High purity (GeS2)80−x(Ga2S3)20·xPrCl3 (x= 1,2,3), (GeS2)79(Ga2S3)20Pr6O11 glasses were prepared and their basic thermal and optical properties were detemuned. The glass transition temperature Tg is in the region 399–404°C. The glass-forming criteria (ΔT ∈ (123–128°C), Hr ∈ (0.59–0.66), S ∈ (2.37–3.29) are changed by Pr doping only a little. The short-wavelength absorption edge lies near 2.7 eV, the doping by Pr creates new absorption bands which can be assigned to the 3H4-3H6, 3H4-3F3, 3H4-3F4, 3H4-3P0 and 3H4-3P1 electron transitions. The experimentally found oscillator strengths calculated from absorption spectra lies between those of Pr doped halide and chalcohalide glasses. The long-wavelength absorption edge was found near 800–1000 cm−1 and it corresponds to multiphonon Ge-S and Ga-S vibrations. The far-IR diffuse reflectance spectra were measured and the spectrum revealed by Kubelka-Munk method. The spectrum was deconvoluted into several bands which can be assigned to GeS4 and GaS4 tetrahedra vibrations. The narrow luminescence bands corresponding to electron transitions in Pr3+ ions (20000, 17857, 15873, 15220, 14326, 13947 and 13459 cm−1) with the most intensive band near 15220 cm−1 were found. These bands can be assigned to the transitions from the 3P0 and 1D2 levels to 3F4, 3F3, 3F2, 3H6, 3H5 and 3H4 levels. The most intensive band corresponds to the 3P0-3F2 transitions.

Intense near-infrared and midinfrared luminescence from the Dy3+-doped GeSe2–Ga2Se3–MI (M=K, Cs, Ag) chalcohalide glasses at 1.32, 1.73, and 2.67 μm

The intense 1.32, 1.73, and 2.67 μm near-infrared and midinfrared emissions were observed from the Dy3+-doped GeSe2–Ga2Se3–MI (M=K, Cs, Ag) chalcohalide glasses. These glasses are red light transparent therefore can be pumped by a semiconductor lasers operating at ∼808 nm. The 2.67 μm emission has not been reported yet which corresponds to an absorption minimum in fluoride fibers and can be very useful for long distance communications. The intensity of emissions is very sensitive to the local chemical environment of Dy3+ ions embedded in these metal halide modified glasses. A plausible correspondence between the emission intensity and the average oscillator strength was found.

Synthesis and properties of GeS2–Ga2S3:NdCl3 and GeS2–Ga2S3:Nd2O3 glasses

Abstract High purity (GeS2)80−x(Ga2S3)20·xNdCl3 (x=1, 2, 3) and (GeS2)79(Ga2S3)20·Nd2O3 glasses were prepared and their thermal and optical properties measured. The GeS2–Ga2S3 glasses can dissolve relatively large amounts of NdCl3 and Nd2O3 (≤3 mol%) and still form stable glasses. They are optically transparent in the range from 19000 cm−1 to 800 cm−1. The glass transition temperature (Tg≅378°C) and the glass-forming criteria are only slightly changed by Nd doping (ΔT=147°C, Hr=0.78; H′=0.39, S=4.10 K, where ΔT=Tc−Tg, Hr is Hrubys criterion, Hr=(Tc−Tg)/(Tm−Tc), H′=(Tc−Tg)/Tg, and S=(Tc−Tx)(Tc−Tg)/Tg). The short-wavelength absorption edge lies near 2.7 eV, doping with Nd creates new absorption bands which can be assigned to electron transfer from the 4 I 9/2 level to 4 G 7/2, 4 G 9/2, 2 K 13/2, 2 G 5/2, 2 G 7/2, 2 H 11/2, 4 F 9/2, 4 F 7/2, 4 S 3/2, 2 H 9/2, 4 F 5/2, 4 F 3/2, 4 I 15/2, 4 I 13/2 and 4 I 11/2 levels. In doped glasses, several broad luminescence bands, near 910, 1080 and 1360 nm, were found, which can be assigned to the transitions from 4 F 3/2 to 4 I 9/2, to 4 I 11/2 and to 4 I 13/2 electron levels. The long-wavelength absorption edge was found near 1000 cm−1 and is due to multiphonon Ge–S and Ga–S vibrations.

Low temperature photoluminescence of Ga0.84In0.16As0.22Sb0.78 solid solutions lattice matched to InAs

Low-temperature photoluminescence (PL) study of liquid phase epitaxy grown undoped and Sn doped GaIn0.16As0.22Sb layers lattice matched to InAs is reported. The quaternary solid solutions Ga1−xInxAsySb1−y are promising materials for the fabrication of optoelectronics devices operating in the spectral range 3–5 μm because these alloys can form type II heterojunctions both with staggered and broken-gap alignment. The band structure engineering of these devices requires the knowledge of energy gaps and mechanism of radiative recombination transitions in the forbidden gap of cladding layers. The high quality quaternary GaIn0.16As0.22Sb epitaxial layers with low native defect concentration were grown lattice matched to InAs and their photoluminescence was studied at low temperatures. The emission band related to bound exciton was dominant. While the emission bands associated with the first ionization state of VGaGaSb vacancy-antisite defect with activation energy ΔEA=22 meV and unknown deep defect with ΔEB=46 ...

Electroluminescence and photoelectric properties of type II broken-gap n-In(Ga)As(Sb)/N-GaSb heterostructures

Layers of n-InAs and n-InGaAsSb were grown by metalorganic vapor phase epitaxy and liquid phase epitaxy on N-GaSb substrates. The electroluminescence, current-voltage characteristics and photocurrent spectra of these heterostructures were studied at low temperatures. It was shown that GaSb/In(Ga)As(Sb) with InAs-rich narrow-gap solid solutions are broken-gap heterojunctions of type II at 77 and 300 K. Intense electroluminescence of the N-GaSb/n-In(Ga)As(Sb) heterostructures was found in the spectral range of 3–4 μm at 77 K. The origin of radiative recombination at the N-n type II broken-gap heterointerface is proposed and is in agreement with the experimental results for both systems.

Origin of recombination transitions at the lattice‐matched GaInAsSb‐GaSb n‐N type‐II heterojunctions

Luminescence properties of GaSb‐GaInAsSb isotype type‐II heterojunctions with various dopings have been investigated. GaInAsSb n‐type epitaxial layers were grown by liquid‐phase epitaxy on Czochralski‐grown N‐type substrates with different tellurium concentrations. Two main luminescent peaks with mutual interchange of intensity and with wavelength shift were observed, both with temperature and excitation intensity. This effect is dependent on dopant concentration in the substrate, as well as in the layer. The explanation of this effect is based on the dominant role of double acceptor levels as final states for the luminescent transitions. A new band in the luminescence spectra was found which is interpreted as a tunneling recombination of the conduction electrons with the photoexcited holes trapped on native acceptors in the band‐bending region at the GaSb side of the heterojunction.

Optical and Spectroscopic Properties of Polymer Layers Doped with Rare Earth Ions

This chapter deals with description properties of a number of Rare-Earth (RE) ions in polymer materials. The list of the RE elements with some of its basic properties are shown in Table 1. The electronic structure of each trivalent RE element consists of partially filled 4f subshell, and outer 5s2 and 5p6 subshell. With increasing nuclear charge electrons enter into the underlying 4f subshell rather than the external 5d subshell. Since the filled 5s2 and 5p6 subshells screen the 4f electrons, the RE elements have very similar chemical properties. The screening of the partially filled 4f subshells, by the outer closed 5s2 and 5p6 subshell, also gives rise to sharp emission spectra independent of the host materials. The intra-subshell transitions of 4f electrons lead to narrow absorption peaks in the ultra-violet, visible, and near-infrared regions.

Optical properties of Er:YAG and Er:YAP materials and layers grown by laser

Optical properties of Er:YAG and Er:YAP materials and layers were studied. Layers were grown by KrF laser ablation (248 nm, 20 ns) from Er-doped targets. Composition, crystallinity, luminescence and results of spectroscopic ellipsometry are discussed. Films were mostly amorphous for substrate temperatures up to ~ 975 °C. Luminescence corresponding to Er+3 ions was observed on all samples. Waveguiding properties were estimated.

Physico-chemical and optical properties of Er3+-doped and Er3+/Yb3+-co-doped Ge25Ga9.5Sb0.5S65 chalcogenide glass

Abstract We investigated the physicochemicаl properties, structure and optical properties of the Ge25Ga9.5Sb0.5S65: Er3+/Yb3+ glasses. The Judd-Ofelt theory was used to calculate the intensities of the intra-4f electronic transitions of Er3+ ions. We observed the upconversion photoluminescence (UCPL) at 530, 550, 660 and 810 nm under 980 nm excitation. In the Ge25Ga9.5Sb0.5S65: 0.1 at.% Er3+, we found that the Stokes photoluminescence (PL) at the green spectral region excited by the 490 and 532 nm laser is only ≈5 times higher than the UCPL emission under 810 or 980 nm excitation making these materials attractive for UCPL applications. The addition of 0.1–1 at.% of Yb3+ into Ge25Ga9.5Sb0.5S65: 0.1 at.% Er3+ glass reduces the UCPL as well as the Er3+ ≈1.5 μm emission intensity probably due to the reabsorption processes of the excitation light and concentration quenching. However, the observed Er3+: 4S3/2→4I13/2 (≈850 nm) emission in the Ge25Ga9.5Sb0.5S65: 0.1 at.% Er3+ sample populates the 4I13/2 level, which promises the using of this material for the 1.5 μm optical amplification.

Solution-processed Er3+-doped As3S7 chalcogenide films: optical properties and 1.5 μm photoluminescence activated by thermal treatment

We report on the optical properties of Er-doped As3S7 chalcogenide films prepared using the two step dissolution process utilizing the As3S7 glass dissolved with propylamine and by further addition of the tris(8-hydroxyquinolinato)erbium(III) (ErQ) complex acting as an Er3+ precursor. Thin films were deposited by spin-coating, thermally stabilized by annealing at 125 °C and further post-annealed at 200 or 300 °C. The post-annealing of films at 200 °C and 300 °C densifies the films, improves their optical homogeneity, and moreover activates the Er3+:4I13/2 → 4I15/2 (λ ≈ 1.5 μm) PL emission at pumping wavelengths of 808 and 980 nm. The highest PL emission intensity was achieved for As3S7 films post-annealed at 300 °C and doped with ≈1 at% of Er which is beyond the normal Er3+ solubility limit of As–S melt-quenched glasses. The solution-processed deposition of the rare-earth-doped chalcogenide films utilizing the organolanthanide precursors has much potential for application in printed flexible optoelectronics and photonics.