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A semiconductor PbS quantum-dots-doped is fabricated using modified chemical vapour deposition in combination with atomic layer deposition. Its photoluminescence properties and unsaturable absorption loss are analysed. It exhibits distinct absorption peaks at 586, 738, and 1048 nm and broadband luminescence in the range 1100–1300 nm. Its full-wave at half-maximum (FWHM) is approximately 130 nm, and its saturable and unsaturable absorption values at 980 nm are 3.82 and 0.75 dB/m, respectively. Furthermore, its figure of merit pump absorption is approximately 83.6%. This is a high, useful pump absorption, and this fibre may be used for novel active optical fibre materials. [ABSTRACT FROM AUTHOR]

The effect of heat treatment on the optical properties of a PbS-doped silica optical fibre was investigated. The experimental results showed that the absorption peak of the fibre red shifted from 1032 to 1133 nm when the heat treatment temperatures were carried out at 900, 950, 1000, and 1100 °C for 1 h, respectively. At the same time, when the heat treatment at 900 °C was carried out for 2, 5, 10, 20, and 40 h, the absorption spectra of the fibre showed a red shift from 1074 to 1143 nm. In addition, the intensity of the absorption peak increased from 0.258 to 1.384 dB/m and the full width at half maximum (FWHM) became narrower (from 130 to 50 nm) as the heat treatment proceeded. Moreover, the photoluminescence (PL) intensity in the wavelength range of 1100–1500 nm decreased with an increase in the heat treatment temperature. The theoretical analysis, using an effective mass method, showed that the effective band gap energy and average size of the lead sulphide (PbS) quantum dots (QDs) in the silica fibre core varied from 1.199 to 1.083 eV and from 4.28 to 4.81 nm, respectively. The results indicate that the size of the PbS QDs present in the silica fibre core could be controlled by a proper heat treatment, which is of great interest in optical fibre amplifiers and other fibre optic devices. [ABSTRACT FROM AUTHOR]

Optical properties of PbS-doped silica optical fiber materials and theoretical simulation are investigated. PbS is deposited on silica optical fiber materials by Atomic Layer Deposition (ALD) technique with Pb(tmhd) 2 and H 2 S as Pb and S precursors, respectively. Its stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence states of S and Pb element are −2 and +2, respectively. The Raman spectra further reveal that PbS has been doped into optical fiber materials almost without destroying irregular rings structure in silica material network. And there are distinct absorption bands at 248 and 352 nm. Fluorescence spectra are obtained with 330 and 350 nm pumping, two fluorescence peaks at 768 and 808 nm, respectively. In addition, the microstructure models for PbS-doped optical fiber materials are built on Gaussian09 platform, and its optical properties of the absorption and emission spectra are calculated using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. There are obvious absorption and emission peaks at 325.7 and 769.8 nm, respectively, which are in good agreement with experiments. [ABSTRACT FROM AUTHOR]

Abstract: A PbS quantum dot coated (QD-coated) tapered fiber amplifier with a broad bandwidth is theoretically demonstrated. The QD layer is coated on the surface of a tapered fiber and is excited by the evanescent wave of a pump. An optical gain of 10.5dB, with a 160-nm broad bandwidth of at 1530-nm center wavelength, is achieved. The gain efficiency is over 4dB/cm. This QD-tapered fiber amplifier has a concentration control of the QDs, a lower insertion loss, and shows good suppression of amplified spontaneous emission (ASE), while its structure is also quite simple. Therefore, the proposed fiber amplifier has great potential in fiber-optic communication systems. [Copyright &y& Elsevier]

• The size of PbS nanocrystals varied with the increase of ALD growth cycles. • Annealing treatment was applied to PbS QDs for regulating PL characteristics. • As-prepared PbS QDs exhibited a tunable broadband wavelength range of 1000–1600 nm. • The PL lifetime variation of PbS QDs prepared by ALD technique was first reported. Lead sulfide (PbS) quantum dots (QDs) were deposited onto silica substrates by atomic layer deposition (ALD). By controlling the number of growth cycles, the average size of the PbS nanocrystals (NCs) changed from approximately 6.3 to 95.4 nm. The crystalline phase of the PbS semiconductor materials was investigated via X-ray diffraction, and it was established that as the size of the NCs increased, the preferred growth orientation of the PbS films was (2 0 0). The obtained nanofilms were compact and continuous polycrystalline films with well-defined grain boundaries. To control the size of PbS QDs further, the temperature-induced characteristics of the ALD-fabricated PbS QD films were studied through annealing. Slow growth of the PbS QDs was observed for the nanofilms annealed at temperatures below 300 °C, whereas the QD size increased significantly at annealing temperatures above 300 °C. The broad near-infrared luminescence wavelength of the PbS nanofilms was tuned from 1000 to 1600 nm. Moreover, the photoluminescence lifetime of the annealed PbS QDs increased from 4.96 to 10.92 μs. The temperature-induced and size-controlled PbS QDs are ideal materials for application in wavelength-tunable optical devices. [ABSTRACT FROM AUTHOR]

• Formation mechanisms for PbS nanomaterials grown on silica substrate are studied by DFT. • PbS are doped into the fiber core via ALD, with nanostructure confirmed by HRTEM. • PbS-doped fiber exhibits fluorescence property at 1060–1370 nm with 1064 nm pumping. • PbS-doped fiber amplifier exhibited a signal gain as 9.4 dB at 1310 nm. The formation mechanisms for lead sulfide (PbS) semiconductor nanomaterials grown on silica substrate were investigated using density functional theory. There are two main reaction processes for the adsorption of Pb(tmhd) 2 on a silica substrate and the reaction with H 2 S to form PbS. The activation barriers of the two reaction processes were quite low at 10.1923 and 20.6778 kcal/mol, which is energetically favorable for PbS deposition by atomic layer deposition (ALD). In addition, PbS nanomaterials were introduced both on silica substrate and into the core of the silica fiber via ALD, with Pb(tmhd) 2 and H 2 S as precursors. The structural properties of the PbS nanomaterials and optical properties of the PbS-doped fiber were characterized. There were obvious absorption peaks at 480, 695, and 1043 nm. The fiber exhibited photoluminescence at 1060–1370 nm with 1064 nm pumping. A gain of 9.4 dB was obtained at 1310 nm, which can be attributed to the PbS nanomaterials in the fiber core. This is crucial for optical fiber communications. [ABSTRACT FROM AUTHOR]