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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]

Post-treatments by ionizing radiations have been proposed previously for regulating the properties of bismuth/erbium co-doped optical fiber (BEDF). In this work, the effects of common ionizing radiations (i.e. gamma ray, electron beam and mixed γ/neutron) on Bismuth Active Centers (BACs) in BEDF have systematically been investigated. Our experimental results show obvious BAC activation by ionizing radiation – evident from the increase in saturable absorption at 830 nm that is closely associated with the BAC responsible for the desirable near infrared (NIR) emissions. This radiation induced BAC activation has been confirmed from the emission of BAC associate with silica (BAC-Si). The saturation pump power of the BAC-Si emission in all irradiated samples is found higher than that in pristine (or non-irradiated) samples. In addition, the effect on emission by different radiation is found in the order of gamma ray > mixed gamma/neutron > electron beam. On the other side, we have also observed significant radiation induced unsaturable loss that can affect the pumping efficiency and Figure of Merit (FOM). • Post-treatment by ionizing radiation has been proposed for regulating the properties of bismuth/erbium co-doped optical fiber (BEDF). • Ionizing radiation effect upon BEDF was investigated in terms of radiation type and dose, doping level, and bismuth active center (BAC) types. • The ionizing radiation will offer alterative way to control and regulate the formation of BAC. • It will provide more information for the better understanding of BAC and ultra-broadband application of BEDF. [ABSTRACT FROM AUTHOR]

• Twin core Bi/Er co-doped silica optical fibre (TCBEDF) was manufactured using 3D printing; • The approach avoided the tedious steps greatly simplifying the manufacturing process of preforms; • The fabricated TCBEDF has potential emission and sensing applications; • The polarized ultra-broadband luminescence was obtained; • 3D printed TCBEDF was used to construct a Mach–Zehnder interferometer (MZI) for sensing. With the advent of the smart information network, optical fibre is evolving from a telecommunication medium to a network device with multiple functions, from laser amplification to distributed sensing. This increasing added function of optical fibre is posing new challenges for specialty optical fibre manufacture. In this article, twin core bismuth and erbium co-doped silica optical fibre (TCBEDF) was manufactured using 3D printing technology. This approach effectively avoided the tedious steps involved with traditional chemical vapour deposition (CVD) technology, such as deposition, doping and drilling, greatly simplifying the manufacturing process of optical fibre preforms. The fabricated TCBEDF has potential emission and sensing applications. The broadband luminescence over wavelength span Δλ ∼ 950–1600 nm was obtained under laser excitation at λ = 830 nm. At the same time, the dual core structure, despite some distortion in profile, provided a polarized ultra-broadband fluorescence. In addition, the dual core structure was used to construct a Mach–Zehnder interferometer (MZI) to demonstrate the sensing of multiple parameters, including temperature, refractive index, stress and bending. [ABSTRACT FROM AUTHOR]

• The local structure models of PbS/PbSe co-doped fiber materials are built based on density functional theory. • PbS/PbSe nano-semiconductor co-doped silica fiber exhibites broadband luminescence enhancement at 1000–1380 nm and achieved a net gain of 14.5 dB at 1160 nm. • PbSe co-doping improves the deposition environment of PbS and increases the density distribution of nanoparticles. A PbS/PbSe nano-semiconductor co-doped silica fiber (PbS/PbSe DSF) was prepared and the enhancement mechanism of fluorescence and gain characteristics were investigated. PbS/PbSe DSF showed the broadband luminescence ranging from 1000 nm to 1380 nm, and the fluorescence intensity at 1160 nm and 1300 nm was enhanced by 15.8 dB and 14.6 dB, respectively. The on–off gain of PbS/PbSe DSF is 13.7–18.9 dB in the range of 1100–1350 nm and the net gain is 10.7–14.5 dB under 980 nm pumping. Simultaneously, based on density functional theory (DFT), local structural models of PbS/PbSe co-doped fiber materials were built, and the study showed that the introduction of PbSe increased the absorption at 969 nm and the corresponding emission in the range of 1100–1400 nm. Moreover, microstructural characterization showed the presence of high-density nanoparticle distribution in the core of PbS/PbSe DSF, indicating that the PbSe co-doping may have changed the local field environment of PbS deposition and increased the crystallinity, which finally improved the fiber performance. The results indicate that the proposed PbS/PbSe DSF is a potential gain material with important research value in areas such as active fiber amplifiers. [ABSTRACT FROM AUTHOR]

The magneto-optical properties for two kinds of novel doping silica optical fibers, Pb-doped optical fiber and Eu-doped optical fiber, are investigated. A measurement system is set up to analyze the Verdet constants of fiber samples, including Pb-doped optical fiber, Eu-doped optical fiber, single mode optical fiber (SMF) and Er-doped optical fiber (EDF). The system keeps extinction ratio (ER) and power of input linearly polarized light stable. For Pb-doped optical fiber and Eu-doped optical fiber, their Verdet constants are larger than that of SMF at different wavelengths (660, 808, 980, 1310, and 1550 nm), and their Verdet constants are increased with the decreasing of wavelength. Especially, the Verdet constant of Pb-doped optical fiber is 3.08 rad/T/m at 660 nm, which is 27.80% larger than that of SMF (2.41 rad/T/m) at corresponding wavelength. Verdet constant of Eu-doped optical fiber at 660 nm is −4.56 rad/T/m, which is 34.91% larger than that of EDF (−3.38 rad/T/m), and 89.21% larger than that of SMF at corresponding wavelength. Pb-doped silica optical fiber and Eu-doped silica optical fiber exhibit superior magneto-optical properties compared with SMF. Further, the magnetization of fibers are presented in the temperature range of 4–380 K. The magneto-optical property of Pb-doped optical fiber is more stable to temperature than that of EDF. [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]

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]

To study the performance of the PbS quantum dots (QDs)-doped silica fiber amplifier (PQDFA), here, a model of PQDFA with ultra-broadband gain and low noise is theoretically proposed. Based on this model, the impact of fiber structure, pump/signal power, and PbS QDs properties on the noise figure (NF) of PQDFA is investigated. The simulation results show that pump/signal light power changes the NF of PQDFA by affecting the population inversion level. Besides, the Stokes-shift and doping concentration proportion of QDs also affect the performance of fiber amplifiers. In addition, the gain and NF spectrum of single- and multi-sized PQDFA are simulated and compared. The simulation results show that the working band of PQDFA is determined by the QDs' emission spectra, and wavelength tunability can be achieved by changing the QDs' distribution in fiber. For the multi-sized PQDFA proposed in this paper, under − 10 dBm input signal power, the 3 dB bandwidth, highest gain, and lowest NF in 1300–1500 nm band are 107 nm, 29 dB, and 3.84 dB, respectively. • Theoretical model of PbS quantum dots-doped silica fiber amplifier. • Ultra-broadband gain and low noise multi-sized quantum dots-doped fiber amplifier. • The 3 dB bandwidth in 1300–1500 nm band is 107 nm. • The fluorescence lifetime and Stokes-shift affect the noise figure of amplifiers. • Gain and noise are related to the doping concentration proportion of quantum dots. [ABSTRACT FROM AUTHOR]