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Er-doped optical fiber (EDF) with ultra-broad gain bandwidth is urgently needed given the rapid advancement of optical communication. However, the weak crystal field of the host silica glass severely restricts the bandwidth of traditional EDF at 1.5 μm. In this study, we theoretically explored the introduction of PbS nanomaterials in the silica network assisted with the non-bridging oxygen. This can significantly increase the crystal field strength of Er3+ ions in the local structure, leading to their energy level splitting and expanding the fluorescence bandwidth. Additionally, the PbS/Er co-doped optical fiber (PEDF) with improved fluorescence and gain characteristics was fabricated using modified chemical vapor deposition combined with the atomic layer deposition technique. The presence of PbS nanomaterials in the fiber core region, which had an average size of 4 nm, causes the 4I13/2 energy level of Er3+ ions to divide, increasing the fluorescence bandwidth from 32 to 39 nm. Notably, the gain bandwidth of PEDF greater than 20 dB increased by approximately 12 nm compared to that of EDF. The obtained PEDF would play an important role in the optical fiber amplifier and laser applications. [ABSTRACT FROM AUTHOR]

In active silica optical fibers, improving the solubility and uniformity of non-concentration-quenching luminescence centers is a key strategy to achieve high gain fiber amplifiers. Herein, we report a novel Er-doped silica optical fiber (EDF) modified by PbS semiconductor incorporation for the first time. Owing to the bridge role of PbS, Er 2 O 3 nanofilms deposited on the substrate via atomic layer deposition (ALD) have porous and loosely layered network structures with an increasing number of ALD-PbS layers. Subsequently, during the high-temperature fiber preparation process, this loose porous structure aids the dissolution and provides an optimal local environment of Er3+ ions in the silica matrix. As a result, the maximum phonon energy of the silica network for PbS/Er co-doped silica optical fiber (PEDF) is reduced, resulting in an increase of the Er3+ ion fluorescence lifetime, approximately 11.455 ms. Furthermore, we achieved 34 dB maximum gain of PEDF sample with the lowest noise figure of 3.9 dB at 1.5 μm. The gain bandwidth over 20 dB of PEDF is approximately 46 nm, which is nearly 44% higher than that of EDF. These results indicate that the PEDF prepared by structural manipulation has great potentials in optical fiber amplifier and laser applications. • Porous PbS/Er co-doped nanofilms were prepared and characterized. • PbS and Er co-doped silica fibers (PEDF) were fabricated for the first time. • Er3+ ions in PEDF show more uniform distribution and higher fluorescence efficiency. • PEDF has the high gain of 34 dB and low NF of 3.9 dB in the amplification system. • Gain bandwidth of PEDF are increased by 44% compared to the non-PbS doped EDF. [ABSTRACT FROM AUTHOR]

The effects of ultraviolet irradiation on luminescent centres in bismuth-doped (BDF) and bismuth/erbium co-doped (BEDF) optical fibers were examined in this study. The fibers were fabricated by modified chemical vapor deposition combining with atomic layer deposition method. The fibers were exposed to irradiation from a 193 nm pulsed wave argon fluoride laser, and an 830 nm wavelength laser diode pump source was employed for excitation. The experimental results showed that, for the BDF, the transmission loss was slightly reduced and the luminescence intensity was increased at the bismuth-related active aluminum centre (BAC-Al). Then, for the BEDF, the transmission loss was increased a little and the luminescence intensity was also increased at the BAC-Al centre. However, the luminescence intensity was decreased at approximately 1420 nm of the bismuth-related active silica centre (BAC-Si) for all fiber samples. One possible formation mechanism for luminescence intensity changes was probably associated with the valence state transfer of bismuth ions. The other possible mechanism was that the ArF-driven two-photon process caused luminescence changes in BAC-Al and BAC-Si. It was very important to reveal nature of luminescence properties of Bi-doped and Bi/Er co-doped optical fiber. [ABSTRACT FROM AUTHOR]

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 Bi/Al-codoped silica optical fibers are fabricated by atomic layer deposition (ALD) doping technique combing with conventional modified chemical vapor deposition (MCVD) process. Bi 2 O 3 and Al 2 O 3 are induced into silica optical fiber core layer by ALD technique, with Bis (2,2,6,6-tetra-methyl-3,5-heptanedionato) Bismuth(III) (Bi(thd) 3 ) and H 2 O as Bi and O precursors, and with Al(CH 3 ) 3 (TMA) as Al precursor, respectively. The structure features and optical properties of Bi/Al-codoped silica optical fibers are investigated. Bi 2 O 3 stoichiometry is confirmed by X-ray photoelectron spectroscopy (XPS). The valence state of Bi element is +3. Concentration distribution of Si, Ge and O elements is approximately 24–33, 9 and 66 mol%, respectively, in fiber preform core and cladding layer region. Bi and Al ions have been also slightly doped approximately 150–180 and 350–750 ppm in fiber preform core, respectively. Refractive index difference of the Bi/Al-codoped fiber is approximately 0.58% using optical fiber refractive index profiler analyzer. There are obvious Bi-type ions absorption peaks at 520, 700 and 800 nm. The fluorescence peaks are at 1130 and 1145 nm with 489 and 705 nm excitations, respectively. Their fluorescence lifetimes are 701 and 721 μs, respectively. And then there are obvious fluorescence bands in 600–850 and 900–1650 nm with 532 nm pump exciting. There is a maximum fluorescence intensity peak at 1120 nm, and its full wave at half maximum (FWHM) is approximately 180 nm. These may mainly result from the interaction between Bi and Al ions. The Bi/Al-codoped silica optical fibers would be used in high power or broadly tunable laser sources, and optical fiber amplifier in the optical communication fields. [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]

• 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]

We fabricated a novel Pb/Bi co-doped silica optical fiber using an atomic layer deposition technique in conjunction with a modified chemical vapour deposition process. The fabricated fiber exhibits distinct absorption peaks at 690, 800, 1000 and 1377 nm. An ultra-broad luminescence band with a 10 dB bandwidth of 600 nm from 1050 nm to 1650 nm was achieved using a dual pumps system. The lifetime of the co-doped fiber at 1150 nm is approximately 740 μs. Additionally, a Pb/Bi co-doped fiber with a length of only 0.2 m, pumped at 980 nm exhibits an optical gain ranging from 1010 to 1190 nm with a maximum peak gain of 12 dB. A theoretical model considering the interaction between Pb and Bi ions is proposed to interpret the observed spectral characteristics. There may be a coupling effect and/or energy transfer between Pb and Bi ions during a deleterious non-radiative quenching process. The Pb/Bi co-doped fiber offers a number of advantages compared to a conventional Bi-doped fiber in terms of broadband luminesce, fluorescence lifetime, and gain. Additionally, it can act as a super fluorescence fiber sources for optical amplifiers and novel fiber lasers in the medical and communication fields. • A novel Pb/Bi co-doped silica optical fiber is fabricated using an atomic layer deposition doping technique. • The 10 dB luminescence bandwidth of Pb/Bi co-doped silica optical fiber is up to 600 nm. • A Pb/Bi co-doped fiber with 0.2 m length shows the optical gain is up to 12 dB range from 1010 to 1190 nm. • A theoretical model is proposed to elucidate the effect of the introduction of Pb ions on Bi-doped fiber. [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]