Search

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]

We experimentally investigate the influences of irradiation and annealing process on the microstructure properties of optical fiber cladding material. The electron spin resonance (ESR) results reveal that the defect concentration significantly decreases after silica fiber cladding material is irradiated by ã-rays with a successive thermal annealing process. Raman analysis show the irradiated microstructure of cladding material change little, after irradiation, which indicates that the three- and four-membered rings (3-MRs and 4-MRs) structures are stable. However, after thermal annealing process, Raman spectrum shows that 3-MRs and 4-MRs are reduced obviously, which means that the ring structures are broken after thermal annealing and new stable structures are formed. X-ray diffraction (XRD) also shows that slight crystallization occurs when the annealing temperature is equal to 1000^\circC. We conclude that Si-O bonds around 3-MRs and 4-MRs are easier to fracture, where color centers are formed. We also show the microstructure models explained by the theory of quantum chemistry. [ABSTRACT FROM AUTHOR]

Simple Summary: China is the world's largest producer of food fish, and Chinese consumers have a preference to buy live fish. Live transport of fish is, therefore, a common procedure in aquaculture and is a potential animal welfare hazard. Little has been published on current fish transportation practices in China or the knowledge and attitudes of stakeholders in this industry. Our qualitative study aimed to obtain original information about live transport processes from a cross-section of aquaculture stakeholders in China by conducting individual interviews. Stakeholders were interviewed about their knowledge of live transport and their attitudes towards the welfare of fish. Self-described knowledge of live transport varied between participants with different job types. Most participants had heard of and understood the concept of "animal welfare", but many understood it to only refer to terrestrial livestock, not fish. This suggests that knowledge of fish welfare in the industry may be less than for other farm animals. The findings of this pilot study contribute to a better understanding of live fish transport from a stakeholder point of view. The findings will also assist in informing, educating, and sensitizing stakeholders to the importance of fish welfare during live transport. China is the largest food fish producer in the world. Chinese consumers normally purchase fish that are still alive to ensure freshness. Therefore, the live transport of fish is important in China's aquaculture, although it carries potential risks for animal welfare. This study investigated the attitudes and knowledge of stakeholders within Chinese aquaculture towards the live transport and welfare of fish. Semi-structured interviews were conducted with 12 participants who were involved with the aquaculture industry in China. Most participants self-rated their transport-related knowledge as moderate and had some understanding of animal welfare, although this term was generally considered only relevant to terrestrial animals. Participants' responses indicated that the live transport of fish occurs frequently in China, generally using sealed tanks, plastic bags, and foam boxes, in purpose-built vehicles. Seasonal changes, such as changes in ambient and water temperature, are considered to be important contributors to successful live transport, as well as sufficient oxygen supplies and stocking density. The use of anesthetics was not commonly reported, particularly in food fish, and fish capture is predominantly by conventional dipnets. The health status of transported fish is determined mostly by morphology (body injury, body or eye color, and fin condition), as well as vigor and swimming ability. Our results indicate that live transport poses a number of welfare risks to fish but that participants in the process associated welfare concerns more with terrestrial animals, not fish. [ABSTRACT FROM AUTHOR]

Abstract: We fabricated a silica optical fiber doped with InP sandwiched in the core and the inner cladding layers by using the conventional modified chemical vapor deposition process. We presented the experimental X-ray analysis on the optical properties and found that compound InP was contained in the fiber core after annealing process. Broadband photoluminescence observed in InP doped fiber was well coincided with those coming from the recombination of deep levels in InP. The occurrence of temperature-dependent photoluminescence both at the lower and room temperature would be related with the localized defects and their confinement in the micro-network structure of Si–O–Si. The Raman spectra reveal that Si–O–In vibration would disorder the silica ring structures and enervate their vibrations. [Copyright &y& Elsevier]

A low-noise Brillouin random fiber laser (BRFL) based on dynamic fiber grating (DFG)-assisted self-injection locking (SIL) as a laser carrier for coherent communication is proposed and experimentally demonstrated. The utilization of the DFG-based SIL basically guarantees an innovative purification of ultra-narrow-linewidth laser radiation after the removal of residual random modes from the gain competition, enabling unprecedented long-term frequency-stabilized coherent lasing resonance over a record of 30 s. Consequently, the relative intensity noise of the generated Stokes random laser is significantly suppressed by ∼20 dB, and the frequency/phase noise imposed by random mode hopping is additionally mitigated. Meanwhile, stimulated Brillouin scattering and randomly distributed Rayleigh scattering along the kilometer-long single-mode fiber further suppress laser frequency/phase noise, benefiting the ultra-narrow laser linewidth of 450 Hz. As a proof-of-concept, an 8-Gbaud (32 Gb/s) 16-quadrature amplitude modulation transmission based on the proposed self-injection locked low-noise BRFL as the laser carrier is demonstrated, achieving a low bit error rate of 3.02 × 10 − 5 . The impact of the laser noise on coherent communication is systematically investigated, highlighting the potential in high-capacity coherent communication. [ABSTRACT FROM AUTHOR]

RNA viruses that contain single-stranded RNA genomes of positive sense make up the largest group of pathogens infecting honey bees. Sacbrood virus (SBV) is one of the most widely distributed honey bee viruses and infects the larvae of honey bees, resulting in failure to pupate and death. Among all of the viruses infecting honey bees, SBV has the greatest number of complete genomes isolated from both European honey bees Apis mellifera and Asian honey bees A. cerana worldwide. To enhance our understanding of the evolution and pathogenicity of SBV, in this study, we present the first report of whole genome sequences of two U.S. strains of SBV. The complete genome sequences of the two U.S. SBV strains were deposited in GenBank under accession numbers: MG545286.1 and MG545287.1. Both SBV strains show the typical genomic features of the Iflaviridae family. The phylogenetic analysis of the single polyprotein coding region of the U.S. strains, and other GenBank SBV submissions revealed that SBV strains split into two distinct lineages, possibly reflecting host affiliation. The phylogenetic analysis based on the 5′UTR revealed a monophyletic clade with the deep parts of the tree occupied by SBV strains from both A. cerane and A. mellifera, and the tips of branches of the tree occupied by SBV strains from A. mellifera. The study of the cold stress on the pathogenesis of the SBV infection showed that cold stress could have profound effects on sacbrood disease severity manifested by increased mortality of infected larvae. This result suggests that the high prevalence of sacbrood disease in early spring may be due to the fluctuating temperatures during the season. This study will contribute to a better understanding of the evolution and pathogenesis of SBV infection in honey bees, and have important epidemiological relevance. [ABSTRACT FROM AUTHOR]

Although depressive symptoms are common in PD, few studies investigated sex and age differences in depressive symptoms. Our study aimed to explore the sex and age differences in the clinical correlates of depressive symptoms in patients with PD. 210 PD patients aged 50–80 were recruited. Levels of glucose and lipid profiles were measured. The Hamilton Depression Rating Scale-17 (HAMD-17), the Montreal Cognitive Assessment (MoCA) and the Movement Disorder Society Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS-III) assessed depressive symptom, cognition and motor function, respectively. Male depressive PD participants had higher fasting plasma glucose (FPG) levels. Regarding the 50–59 years group, depressive patients had higher TG levels. Moreover, there were sex and age differences in the factors associated with severity of depressive symptoms. In male PD patients, FPG was an independent contributor to HAMD-17 (Beta = 0.412, t = 4.118, p < 0.001), and UPDRS-III score was still associated with HAMD-17 in female patients after controlling for confounding factors (Beta = 0.304, t = 2.961, p = 0.004). Regarding the different age groups, UPDRS-III (Beta = 0.426, t = 2.986, p = 0.005) and TG (Beta = 0.366, t = 2.561, p = 0.015) were independent contributors to HAMD-17 in PD patients aged 50–59. Furthermore, non-depressive PD patients demonstrated better performance with respect to visuospatial/executive function among the 70–80 years group. These findings suggest that sex and age are crucial non-specific factors to consider when assessing the relationship between glycolipid metabolism, PD-specific factors and depression. [ABSTRACT FROM AUTHOR]

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]

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]

• An optical fiber weak magnetic sensing system based on Michelson interferometer is proposed. • A new improved phase-generated carrier demodulation algorithm. • Suitable for optical fiber interference weak signal demodulation. • The sensing unit support frame was fabricated using 3D printing. The detection of weak magnetic fields is integral to applications in geophysical monitoring, biomagnetism, and remote sensing. This paper presents a new sensing unit structure and signal demodulation algorithm for optical fiber weak magnetic sensing system. The system uses a strip-ring sensing unit structure that combines magnetostrictive effects with optical fibers through 3D printing technology. This integration facilitates the conversion of magnetostrictive displacement into optical phase. An improved Phase Generated Carrier (PGC) algorithm is employed to demodulate the phase information, enhancing the signal to noise ratio (SNR) by 4.33 dB compared to the traditional PGC algorithm, and achieving a phase resolution of 29.51 µrad/Hz1/2 at 500 Hz. Experimental results demonstrate that the suggested sensing system can detect a minimum magnetic field of 140 nT, with an AC magnetic field phase resolution of 15.78 nT/Hz1/2 at 500 Hz. The demodulation sensitivity reaches 1.87 × 10−6 rad/nT under a magnetic field of 140–1400 nT. The capability of the proposed system demonstrated great potential as an efficient approach for detecting weak magnetic signals in many practical applications. [ABSTRACT FROM AUTHOR]

• Reveal the design principles of trench-assisted bridge fibers (TABFs), offering an effective methodology for fabricating TABFs for FIFO devices. • Demonstrate the feasibility of utilizing TABFs for fabricating low-loss FIFO devices. • The results indicated that the fabricated FI/FO device exhibited a remarkably low loss (<0.50 dB), and relatively low crosstalk (<-55.2 dB) in the C-band. Multi-core fibers (MCF) technology is the feasible path to extend the capacity of optical fiber communication systems. However, there is a lack of low-loss and low-crosstalk multi-core fan-in and fan-out (FIFO) devices for MCF communication in the C-band. In this paper, we proposed all-fiber FIFO devices with seven trench-assisted bridge fibers (TABFs). The special structure of the TABFs could facilitate the matching of single-core fiber with MCF during the tapering progress. By using the TABFs, the average taper loss was less than 0.06 dB. The novel method can reduce the insertion loss of FIFO devices. The experiments indicated that the fabricated FIFO devices exhibited lower than 0.50 dB insertion loss and less than −55.2 dB crosstalk in the C-band. This work provides novel TABFs and an efficient way to fabricate low-loss low-crosstalk FIFO devices for MCF communication systems. [ABSTRACT FROM AUTHOR]

A novel approach for producing sidelobe-free optical vortices is proposed, for the first time, utilizing object-oriented computer generated holograms (CGH). By conjugate-symmetrically extending the complex amplitude of any desired optical vortices prior to performing the discrete Fourier transform, the resulting real-valued number profile is encoded into an object-oriented CGH without having conventional forked-shaped fringes. On the basis of the CGH generated, use is first made of numerical simulations to reconstruct optical vortices with spiral phase profiles. Detailed experimental measurements employing a computer-controlled spatial light modulator and extensive numerical simulations are undertaken to verify the proposed technique. Excellent agreements between numerical simulations and experimental measurements are observed. Results show that optical vortices with a single primary intensity ring are generated without the occurrence of any sidelobes in the periphery for absolute values of topological charges as large as 20. [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]

In this paper, we proposed a substrate rotation‐enhanced Raman scattering (SRERS) effect. The substrate, prepared by the technology of texturization and electroplating, is fixed on the motor and rotates with it while collecting Raman signal. The relative standard deviation (RSD) of Raman intensity in multiple measurements is less than 9.1%, which indicates that the Raman signal is stable and reproducible based on the SRERS effect. What is more, this method eliminates the fluctuation of the local electric field intensity caused by the inhomogeneity of the substrate and makes the "equivalent hot spots" distributed uniformly on the whole surface. The quantitative analysis with the Rhodamine 6G (R6G) and the lipid‐soluble drug Oxaprozin (OXA) as the probe respectively has demonstrated that the Raman intensity of R6G at 612 cm−1 with respect to concentration tend to linear ranging from 10−10 to 10−8 mol/L with the correlation coefficient (R2) is more than 0.96, and the Raman intensity of OXA at 1,003 cm−1 with respect to concentration tend to linear ranging from 3.4 * 10−6 to 3.4 * 10−4 mol/L (prepared with 50% v/v ethanol) with the correlation coefficient (R2) is more than 0.97. The mechanism of SRERS is given, and the theory analysis indicates that the Raman signal obtained is the mean of a large number of laser‐scanning points' contributions. [ABSTRACT FROM AUTHOR]

• We theoretically propose a type of ring-core quantum dots doped fiber amplifier (QDFA), capable of providing amplification for a number of LP signal modes. • The annular optical fiber doped with PbS quantum dots not only supports transmission for LP (L=0∼6,1) signal mode group, but also provides relatively uniform gain for LP (L=1∼3,1) signal mode over the wavelength range 1500 nm–1630 nm. • For LP (1,1) , LP (2,1) and LP (3,1) signal modes, we explore the differential modal gain (DMG) under 11 pump mode groups (LP (L=0∼10,1)). • Noticing that the highest gain for LP (1,1) signal mode is about 31 dB obtained at the wavelength of 1530 nm and the DMG is less than 0.5 dB with a LP (7,1) pumping mode. Optical fiber amplifier is a vital device in optical communication system, which can directly amplify optical signal. We theoretically propose a type of few-mode quantum dots-doped fiber amplifier (FM-QDFA) in this paper, capable of providing amplification for a number of linear polarization (LP) signal mode groups. The main part of the amplifier is a ring-core fiber doped with PbS quantum dots. And refractive index difference between the annular area and cladding is set to 0.035, which weakens the modal coupling between different LP mode groups. The simulation results show that the ring-core optical fiber not only supports transmission for LP (L=0∼6,1) signal mode group, but also provides relatively uniform gain for LP (L=1∼3,1) signal mode group across the wavelength band 1500 nm–1630 nm that covers the C + L band. For these three signal modes, we explore the differential modal gain (DMG) under 11 pump mode groups (LP (L=0∼10,1)). Noticing that the highest gain for LP (1,1) signal mode is approximately 31 dB obtained at the wavelength of 1530 nm and the DMG is less than 0.5 dB with a LP (7,1) pumping mode. [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]

We have proposed and demonstrated a cylindrical vector mode (CVMs) based Mach–Zehnder interferometer (MZI) in a vortex fiber (VF) for strain sensing. The VF has a coaxial structure supporting the fundamental mode of the HE11 mode in the center core and the first-order CVMs of TE01, HE21, and TM01 modes in the ring core, respectively. By applying a pair of separated microbend long period gratings (MLPGs), the HE11 mode is partially coupled to the CVMs and then combined for constructing an in-fiber MZI. Three separated interference spectra are observed distinctly corresponding to TE01, HE21, and TM01 modes, which exhibit a good linear response to the strain change. Among these three CVMs, the TE01 mode demonstrates the highest sensitivity of −2.41 nm/mε and temperature insensitivity feature. The low cross-sensitivity from temperature benefits the CVMs based MZI to be an ideal strain sensor without compensation, having potential applications of next-generation sensors in smart engineering structures. [ABSTRACT FROM AUTHOR]

We propose a method combining off-axis digital holography (DH) with one-dimensional (1D) lateral shear based on Zig-zag scanning to extract high-precision phase distribution of biological tissues. Firstly, object wavefront is reconstructed using the numerical reconstruction algorithm from digital hologram. Secondly, Zig-zag scanning is introduced to reorder the object wavefront from matrix to 1D vector, allowing the retrieved phase value to change smoothly without value saltation. Then, 1D lateral shear process is performed to acquire the shear vector, from which the phase difference vector is extracted by arctangent calculation. Given the small amount of shear, the phase difference vector is extracted without unwrapping process. Afterwards, the phase vector is obtained through numerical accumulation. Finally, the real phase distribution matrix is retrieved by inverse Zig-zag scanning. The proposed method has high precision in phase extraction of biological tissues. The simulated and experimental results demonstrate the feasibility and precision superiority of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract Digital holographic tomography (DHT) technology is efficiently utilized to measure optical fiber structure profile. A Mach-Zender off-axis holographic interferometer is used to get fiber wavefront, an angular spectrum reconstruction algorithm is applied to obtain optical path difference (OPD) curves. With an adaptive simultaneous algebraic reconstruction technique (ASART), we obtain a fiber refractive index profile and non-circularity. In fiber wavefront measuring, errors are inevitably caused by measurement accuracy and fiber position offset as fiber rotating. In order to improve fiber structure profile reconstruction accuracy, we propose a novel algorithm to eliminate measuring errors of OPD curves including value drift and position drift, which obviously improves the reconstruction quality. With ASART, we analyze the structure parameters of single-mode spun fiber with various spinning pitches, including refractive index profiles and the fiber non-circularity. The results show that as the shortening of fiber spinning pitch, the refractive index dip in the fiber core is deeper and both cladding non-circularity and core non-circularity are less. [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]

Concanavalin A (Con A)-based hydrogels have been widely studied in the field of glucose detection as Con A can selectively bond to glucose molecules. Many sensors have been proposed for detecting glucose using fluorescence or optical methods. However, these sensors suffer from limited sensitivity and fabrication issues. In this study, a label-free optical-fiber long-period grating-based glucose sensor is proposed. Con A-based UV-curable hydrogel was used as the sensing material, which can be rapidly prototyped using the micro-3D printing technique to realize microscale structures. Polymerized hydrogel grating structures patterned onto the fiber surface can periodically modulate the refractive index of the fiber modes affecting the resonant spectrum of the device. The structures swelled upon the addition of a glucose solution, which caused a wavelength shift in the transmission spectrum. The experiments showed that glucose-induced swelling/deswelling was reversible, and the wavelength versus glucose concentration was linear with a response sensitivity of 0.206 nm/mM over a wide range of 0–25 mM with high linearity (R2 = 0.998). The device works well at room temperature and has a short response time. It has significant potential for use in real time continuous glucose monitoring. • A hydrogel-based long period grating as a glucose sensor is proposed. • The hydrogel glucose sensor is directly printed by a micro DLP 3D printer. • The printed device is selectively sensitive to glucose. [ABSTRACT FROM AUTHOR]

The fabrication and characterization of Si1-xGex core fiber have attracted much attention because of its great application potential in new optoelectronic devices. In this work, by assembling two semi-cylindrical monocrystalline Si and Ge rods into a silica tube, we present a fabrication method to draw Si1-xGex core silica clad fiber with graphite furnace. Raman spectra analysis reveals that in all regions of the core formed the Si1-xGex alloy. The optical microscopic photograph shows that in the core of a diameter of 36 μm distributed the bright and dark regions, where it was further proved by Raman spectroscopy that the bright regions are Ge-rich areas and the dark regions are rich in silicon. By recording the Raman spectra of consecutive regions, it was found that with the increase of Ge content (x<0.5) the peak intensity of Si-Ge mode obviously increases, similar to the intensity of Ge-Ge mode, while the peak intensity of Si-Si mode decreases. Then we made a quantitative analysis of the components and strain by mapping the Raman spectra of the fiber core. The experimental results show that the Ge content mainly distributes between 0.1 and 0.8, concentrating between 0.2 and 0.3, and the strain distribution on the surface is obtained at the same time. [ABSTRACT FROM AUTHOR]

A high performance of anion exchange membranes (AEMs) is highly demanded in anion exchange membrane fuel cells (AEMFCs) and has been extensively studied. However, the poor ionic conductivities and the alkaline stability might limit their applications. Herein, we developed a novel strategy to improve the ionic conductivity and alkaline stability of AEMs by introducing hydrophilic oligo(ethylene glycol)(OEG) groups. Continuous ion-conducting channels were efficiently formed thanks to the dynamic aggregation of water molecules assisted by the hydrophilic side chains. The resultant AEMs with low IEC values showed significant enhancement in hydroxide conductivity compared to the AEMs functionalized by the conventional 1,2-dimethylimidazolium (PSf-Im), as the hydroxide conductivity of PSf-2 membrane with an IEC of 1.05 mmol g −1 was 59.5 mS·cm −1 at 60 °C while the hydroxide conductivity of PSf-Im membrane with an IEC of 1.27 mmol g −1 was 36.7 mS·cm −1 . In addition, the alkaline stability and the mechanical properties of the resultant AEMs were improved remarkably. The density functional theory (DFT) study showed that the introduction of OEG part can significantly increase the LUMO energy of functional group and then enhance the alkaline stability. [ABSTRACT FROM AUTHOR]

Effects of annealing on the residual stresses distribution and structural properties of Si core fiber cross-section are mainly investigated using Raman spectra map, scanning electron microscope (SEM) and X-ray diffraction. The annealing was carried out at 800 °C, 1000 °C, and 1200 °C, respectively by muffle furnace. The experimental results show that defects distribution has more obvious effects than the different characters between core and cladding on the residual stresses at the inner area of Si core cross-section. The defects distribution relate to the temperature field distribution during the process of drawing fiber. Annealing could decrease the residual stresses and make the distribution of residual stresses uniform effectively. For all samples, the Si core annealed at 1200 °C has the smallest residual stresses and the most uniform residual stresses distribution. The residual stresses of 155–437.5 MPa mainly caused by different characters between Si core and SiO 2 cladding distribute at the narrow ring area near the inner surface of cladding. This area is very likely to be composed by grains which is smaller than grains in the inner, and has looser microstructure than the inner. It exists like a buffer layer. Annealing could also improve the crystal quality of Si core. After annealed at 1200 °C, the high intensity diffraction peak of the (3 1 1) plane is generated in the X-ray diffraction spectra. [ABSTRACT FROM AUTHOR]

Abstract: Tiny but highly efficient, a light‐emitting diode (LED) can power a therapy device, such as a phototherapy device, and, at the same time, decrease the device's size requirements. In this study, a LED phototherapy device was designed to investigate the possible impact on wound healing using a mouse model and a cell line exposed to red and blue light. To enhance wound phototherapy, a gelatin sponge was fabricated. Results showed that the red and blue lights promoted cell growth and wound healing, while the blue light with a gelatin sponge protected the wound from infection in the early stages of wound healing. The LED phototherapy device combined with the gelatin sponge, therefore, has potential significance in clinical application for wound healing. [ABSTRACT FROM AUTHOR]

Effect of annealing temperature on the stress and structural properties of a Ge core fibre via the molten core drawing (MCD) method is investigated using Raman spectroscopy, Scanning electronic microscopy (SEM), and X-ray diffraction. The experimental results showed that the Raman peak position of the Ge fibre shifted from 297.6 cm −1 to 300.5 cm −1 , and the FWHM value decreased from 4.53 cm −1 to 4.31 cm −1 , when the annealing is carried out at 700 °C, 800 °C, and 900 °C, respectively. For the Ge core annealed at 900 °C, an apparent crystal grain can be seen in the SEM image, and the diffraction peaks of the (3 3 1) plane are generated in the X-ray diffraction spectra. These results show that optimising the annealing temperature allows the release of the residual stress in the Ge core. When the Ge core fibre is annealed at 900 °C, it exhibits the lowest residual stress and the highest crystal quality, and the quality improvement relative to that of the sample annealed at 800 °C is significant. Hence, annealing at around 900 °C can greatly improve the quality of a Ge core fibre. Further performance improvement of the Ge core fibre by annealing techniques can be anticipated. [ABSTRACT FROM AUTHOR]

Effect of controlling recrystallization from the melt (1000 °C) on the residual stress and structural properties of a Ge core fiber via molten core drawing (MCD) method is investigated. Ge core fibers is investigated using Raman spectroscopy, scanning electron microscope (SEM), and X-ray diffraction (XRD). Compared with the as-drawn Ge fiber, the Raman peak of the recrystallized Ge fiber shift from 300 cm −1 to 300.6 cm −1 and full width at half maximum (FWHM) decreased from 5.36 cm −1 to 4.48 cm −1 . The Ge crystal grains which sizes are of 200–600 nm were formed during the process of recrystallization; the XRD peak of (1 1 1) plane is observed after recrystallization. These results show that controlling recrystallization allows the release of the thermal stress, and improvement of the crystal quality of Ge core. [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]

Hypoxia is a disorder in which the tissues are not oxygenated adequately. The lack of oxygen may cause irreversible damage to the major organs such as the brain, heart and lungs. In severe cases, coma, seizures, and death may happen. In addition to the routine medication, acupuncture treatment has been applied as a complementary treatment to counter hypoxia. In this paper, the optical fiber acupuncture needle was fabricated using the optical fiber imbedding into the metal capillary tube with needle tip, therefore made it easy to insert into the body for the laser treatment. The laser optical fiber needle treatment to the ST36 acupoint conducted with the laser irradiation intra body. The normobaric hypoxia tolerance test results in mice show that the optical fiber needle treatment to the ST36 acupoint with laser acupuncture appears to improve the tolerance to hypoxia. The mice treated with laser acupuncture expressed high level of IL-1 in serum. Our results suggest that laser optical fiber needle acupuncture may serve as a potential treatment for hypoxia. [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]

• A new method is proposed to measure the refractive index profile of planar optical waveguides. • A measurement system is established by integrating the near-field setup and the modified Mach-Zehnder interferometer. • The refractive index profile is quantitatively obtained from two phase difference distributions. • The accuracy of the proposed method is up to 1 × 10−3. A method based on the near-field technique and digital holography is proposed to measure the refractive index profile of planar optical waveguides. A measurement system is established by integrating the near-field setup and the modified Mach-Zehnder interferometer. The near-field intensity profile of optical waveguides is recorded by CCD to get the primary refractive index profile. The primary phase difference distribution is calculated based on the relationship between the phase and refractive index. The digital hologram is acquired by the modified Mach-Zehnder interferometer to extract the real phase difference distribution using the hybrid reconstruction algorithm. According to the relationship between the primary and real phase difference distributions, the refractive index profile is quantitatively obtained. To evaluate the proposed method, we measured the refractive index profiles of multimode and single-mode fibers and compared with S14 based on refracted near-field method and SHR-1802 based on digital holography. The proposed method has a measurement accuracy of up to 1 × 10-3 and is suitable for measuring the positive refractive index region of waveguides. [ABSTRACT FROM AUTHOR]

Due to the significant advancement of transmission networks and related technologies, optical communication with a large capacity is essential. In this study, a few-mode PbS quantum dot-doped fibre amplifier (FM-PQDFA) was developed and numerically studied. The amplifier can effectively amplify the linear polarisation (LP) signal modes, including LP 01 , LP 11 , and LP 21 , in the range 1100–1350 nm. The influences of the quantum dot (QD) doping concentration, fibre length, and signal power on the gain and noise figure (NF) of FM-PQDFA were investigated. In addition, the pump influenced the gain, NF, and differential mode gain (DMG). The results revealed that the gain, NF, and DMG can be optimised by adopting an appropriate pump light mode. When the signal and pump light modes were both LP 01 , the highest gain of 31.6 dB and lowest NF of 3.25 dB were achieved. LP 11 pump mode was the optimal pumping mode to obtain the high gain, low NF and small DMG simultaneously. • A low-noise broadband few-mode PbS quantum dots-doped fibre amplifier was proposed and numerically analysed. It can amplify LP 01,s and LP 11,s evenly in the band ranging from 1136–1316 nm. The gains were higher than 27 dB, the DMG was less than 1 dB and the NFs were lower than 3.35 dB. • The QD doping concentration, fibre length, and signal power are important parameters that affect the performance of FM-PQDFA. • The pump influenced the gain, NF, and differential mode gain (DMG) by affecting the overlap factor between the pump light mode field, signal light mode field, and the area of the doped material; and the gain, NF, and DMG can be optimised by adopting an appropriate pump light mode. • When the signal and pump light modes were both LP 01 , the highest gain of 31.6 dB and lowest NF of 3.25 dB were achieved. [ABSTRACT FROM AUTHOR]

Silica optical fiber cladding materials were experimentally treated by a series of processes. The treatments involved quenching, irradiation, followed by annealing and subsequent re-irradiation, and they were conducted in order to improve the radiation hardness. The microstructural properties of the treated materials were subsequently investigated. Following the treatment of the optical fiber cladding materials, the results from the electron spin resonance (ESR) analysis demonstrated that there was a significant decrease in the radiation-induced defect structures. The ESR signals became significantly weaker when the samples were annealed at 1000 °C in combination with re-irradiation. In addition, the microstructure changes within the silica optical fiber cladding material were also analyzed using Raman spectroscopy. The experimental results demonstrate that the Si O Si bending vibrations at ω 3 = 800–820 cm −1 and ω 4 = 1000–1200 cm −1 (with longitudinal optical (LO) and transverse optical (TO) splitting bands) were relatively unaffected by the quenching, irradiation, and annealing treatments. In particular, the annealing process resulted in the disappearance of the defect centers; however, the LO and TO modes at the ω 3 and ω 4 bands were relatively unchanged. With the additional support of the ESR test results, we can conclude that the combined treatment processes can significantly enhance the radiation hardness properties of the optical fiber cladding materials. [ABSTRACT FROM AUTHOR]

We propose the generation of novel composite vortex beams by coaxial superposition of Laguerre–Gaussian (LG) beams with common waist position and waist parameter. Computer-generated holography by conjugate-symmetric extension is applied to produce the holograms of several composite vortex beams. Utilizing the holograms, fantastic light modes including optical ring lattice, double dark-ring and double bright-ring composite vortex beams etc. are numerically reconstructed. The generated composite vortex beams show diffraction broadening with some of them showing dynamic rotation around beam centers while propagating. Optical experiments based on a computer-controlled spatial light modulator (SLM) verify the numerical results. These novel composite vortex beams possess more complicated distribution and more controllable parameters for their potential application in comparison to conventional optical ring lattice. [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]

Purpose: This work focused on the investigation the hyperthermia performance of the carbon-coated magnetic particles (CCMPs) in laser-induced hyperthermia. Materials and methods: We prepared CCMPs using the organic carbonization method, and then characterized them with transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectrophotometry, vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). In order to evaluate their performance in hyperthermia, the CCMPs were tested in laser-induced thermal therapy (LITT) experiments, in which we employed a fully distributed fiber Bragg grating (FBG) sensor to profile the tissue's dynamic temperature change under laser irradiation in real time. Results: The sizes of prepared CCMPs were about several micrometers, and the LITT results show that the tissue injected with the CCMPs absorbed more laser energy, and its temperature increased faster than the contrast tissue without CCMPs. Conclusions: The CCMPs may be of great help in hyperthermia applications. [ABSTRACT FROM AUTHOR]

Liquid chromatography and mass spectrometry were time-consuming and expensive as the main methods for the drug analysis at present, and the samples must be pretreated. The Raman spectroscopy measurement methods were fast and simple, so the Raman spectroscopy methods for the drug analysis were explored in this paper. An optical fiber nano-probe coated with gold nanoparticles was fabricated and used with surface-enhanced Raman spectroscopy (SERS) to measure levofloxacin lactate. The resulting SERS spectra of levofloxacin lactate in mouse blood that was detected by the optical fiber nano-probe clearly showed the characteristic wave numbers of levofloxacin lactate, indicating that optical fiber nano-probes can be used with spectral techniques to analyze drugs in vitro or potentially even in vivo. Copyright © 2015 John Wiley & Sons, Ltd. [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]

Optical fiber nanoprobe with gold nanoparticles substrate on the surface was prepared by electrostatic self-assembly technology. Surface-enhanced Raman spectrum of the cells was measured using the optical fiber nanoprobe by remote detection method and direct detection method using confocal Raman micro-spectroscopy. The spectrum were analyzed with the detailed chemical components. The remote detection method using the optical fiber nanoprobe could make the probe inserting into the cells or tissue, and that may be helpful for the online SERS measurement of the cells in the biomedical research and diagnosis in the future. [ABSTRACT FROM AUTHOR]

This paper presents a long-period fiber-grating (LPG) based Michelson interferometric refractometry to monitor the change in refractive index of porcine muscle during laser-induced interstitial thermotherapy (LITT). As the wavelength of RI interferometer alters with the change in refractive index around the probe, the LPG based refractometry is combined with LITT system to measure the change in refractive index of porcine muscle when irradiated by laser. The experimental results show the denaturation of tissue alters the refractive index significantly and the LPG sensor can be applied to monitor the tissue state during the LITT. [ABSTRACT FROM AUTHOR]

Abstract: A simple method for coupling light from a laser diode (LD) to multimode fiber (MMF) by using a compact in-fiber mode adapter, which is constructed with double-cladding fiber is presented, for the first time. Strong cladding-mode resonance across the thin-thickness inner cladding is used to excite the cladding modes. Principle of proposed mode adapter is theoretically investigated and its performances are experimentally verified by measurement results. By comparing the direct connection between LD and MMF, the coupling efficient of transmission power is improved by using our proposed adapter. [Copyright &y& Elsevier]

Highlights: [•] We fabricated Nb/Al codoped silica fiber with ALD and MCVD. [•] We fabricated long-period grating (LPG) in this fiber with CO2 laser pulse. [•] We studied the temperature and strain characteristics of this Nb/Al-LPG. [•] Acquired thermooptic coefficient of the of Nb/Al fiber core is 7.99×10−6/°C. [•] Acquired elastooptic coefficient of the of Nb/Al fiber core is −0.222. [ABSTRACT FROM AUTHOR]

Abstract: We theoretically analyzed the gain characteristics of an integrated semiconductor quantum dot (QD) fiber amplifier (SQDFA) by using a 2×2 tapered fiber coupler with a PbS QD-coated layer. The asymmetric structure of the fiber coupler is designed to have a maximum working bandwidth around 1550-nm band and provide a desired optical power ratio of the output signals. By using 600mW of 980-nm pump, 10dB gain of a 1550-nm signal is estimated with the gain efficiency of 4.5dB/cm. [Copyright &y& Elsevier]

This paper presents a long-period fiber-grating (LPG) based Michelson interferometric refractometry to monitor the change in refractive index of porcine muscle during laser-induced interstitial thermotherapy (LITT). As the wavelength of RI interferometer alters with the change in refractive index around the probe, the LPG based refractometry is combined with LITT system to measure the change in refractive index of porcine muscle when irradiated by laser. The experimental results show the denaturation of tissue alters the refractive index significantly and the LPG sensor can be applied to monitor the tissue state during the LITT. [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]

Abstract: Mobile wireless optical communication system was demonstrated experimentally by using a special solid coupling optical taper. The performance of special solid coupling optical taper and the data transmission performance with 240Mbit/s were investigated on the rectilinear orbit between the mobile terminal and the fixed terminal. The experimental results shown that the scheme used in the mobile wireless optical communication system is reliable and quite simple, which could be widely used in future. [Copyright &y& Elsevier]

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]

• The application of reduced tillage plus organic manure promoted soil aggregation. • SOC and its active fractions were preferentially fixed in macroaggregates. • Reduced tillage plus organic manure improved the quantity and quality of SOC. Studying the impact of tillage and fertilization on soil organic carbon (SOC) content and aggregate is essential to define better strategies for improving soil structure and SOC sequestration. A field experiment was conducted for 9 years to investigate effects of different tillage and fertilization management practices on SOC and its active fractions [labile organic carbon (LOC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC)] within the bulk soil and in soil aggregates under rice (Oryza sativa L.)–wheat (Triticum aestivum L.)-based cropping systems. Five treatments were included: conventional tillage with no fertilizer (CT), conventional tillage with chemical fertilizer (CTFR), reduced tillage with chemical fertilizer (RTFR), conventional tillage with organic manure (CTOM), and reduced tillage with organic manure (RTOM). The results showed that the organic manured plots (CTOM and RTOM) significantly increased the concentrations of SOC and active carbon fractions (LOC, DOC and MBC) within the bulk soil and soil macroaggregates, and increased the mass proportion of macroaggregates (>250 μm) compared with chemical fertilizer treatments (CTFR and RTFR) or CT. The highest SOC concentration and macroaggregates (>250 μm) were observed in CTOM. The increased SOC, especially active carbon fractions, was mainly concentrated in soil macroaggregates (>250 μm). Soil aggregates were dominated by macroaggregates (>250 μm), which had higher MBC and lower PAOC (the percentage of slow plus passive carbon fractions) after 9 years of RTOM treatment than after CT or CRFR treatment. The results indicated that RTOM played a positive role in promoting the formation of the soil macroaggregate structure. By studying the responses of SOC and water-stable aggregate contents to different tillage and fertilization managements, the continual application of organic manure may be feasible and the periodic organic manure addition may be combined with reduced tillage practice to produce an integrated soil management strategy for the paddy–upland rotation region in Middle China. [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]