Doped Silica Research Articles

Волоконные лазеры с солнечной накачкой без первичного концентратора.

We studied solar pumped fiber lasers without primary concentrator. A model of solar sidepumped Nd3+ doped silica fiber lasers was developed using photon tracing method. Theabsorbed power distribution, possible losses and the pumping efficiency are estimated using the model. We analyzed the estimated paramters and drawed conclutions which have many suggests for improved design of solar pumped fiber lasers. The absorption efficiency of a fiber solar laser without a primary concentrator or sun tracker was calculated to be 0.2% for a 190 m fiber. The output power of the fiber laser is 40 mW, and the conversion efficiency from sunlight to laser light is calculated to be 0.06%. The developed model allows one to estimate the overall efficiency, output power and absorption distribution of Nd3+ fiber lasers without focusing optics, enabling various investigative comparisons.

Luminescent properties of Tb3+ doped sodium silica germanate glasses

Luminescent properties of Tb3+ doped sodium silica germanate glasses

Warm to cool tunable ultra-stable white light emissions from carbon dots -Tb3+ - Eu3+ doped silica

Development of ultra-stable, solid-state, cost-effective phosphors for white light emitting devices with high color rendition is in high demand. In this work, we prepared carbon quantum dots (CQDs) by a hydrothermal method with an average size ranging from 2 to 8 nm which exhibits low toxicity. Optical analysis confirmed the influence of both Cu2+ and Fe3+ ions and the excitation-dependent fluorescence of CQDs are effectively quenched by addition of Fe3+ ions. The excitation dependent emission property of CQDs and degradation resistant blue emission of CQDs-silica are utilized to construct CQDs-Europium–Terbium doped silica matrices for stable multi-colour emissions upon different excitation wavelengths. Optimized composition of CQDs with Terbium and Europium ions produced white light emissions under UV exposure of 370–393 nm. Continuous tuning from warm white emission to cool white emission with moderate CRI is achieved by varying the concentration of CQDs. The ultra-stable white emissions which last long for a year, reveals the potential WLED applications of these solid-state luminescent materials.

Low-loss fiber-to-chip edge coupler for silicon nitride integrated circuits.

Silicon nitride (SiN) integrated optical waveguides have found a wide range of applications due to their low loss, broad wavelength transmission band and high nonlinearity. However, the large mode mismatch between the single-mode fiber and the SiN waveguide creates a challenge of fiber coupling to these waveguides. Here, we propose a coupling approach between fiber and SiN waveguides by utilizing the high-index doped silica glass (HDSG) waveguide as the intermediary to smooth out the mode transition. We achieved fiber-to-SiN waveguide coupling efficiency of lower than 0.8 dB/facet across the full C and L bands with high fabrication and alignment tolerances.

Controlled synthesis and superior UV-visible photocatalytic activity of carbon quantum dots encapsulated with silica

• Synthesis of C-QDs was performed from dehydration of Glucose-D in concentrated sulphuric acid at room temperature. • Silica encapsulated C-QDs were carried out in situ, followed by high temperature calcination. In this work, we report a facile one-step approach to prepare carbon quantum dots doped silica. Carbon quantum dots (C-QDs) were synthesized using Glucose as precursor and sulfuric acid (98%) as carbonating agent in aqueous medium. The encapsulation of C-QCDs was then achieved by in situ hydrolysis of precursor Tetraethyl orthosilicate (TEOS) through Solgel method. The structural studies of C-QDs doped silica was done by powdered X-ray diffraction ( p -XRD). The optical characterization of the prepared C-QDs was performed by Ultraviolet-visible (UV-vis) spectroscopy. Consequently, the as-prepared C-QCDs were found to be highly fluorescent with little crystallinity. The morphological investigation of as-made silica and C-QCDs doped silica was studied by field emission scanning electron (FSEM). In order to study photodegradation studies methylene blue was used as model compound. C-QCDs doped silica showed higher degradation (98.5%) in comparison to the pristine C-QDs (38%) and silica (76%) in neutral media.

Aggregation of ODC(I) and POL Defects in Bismuth Doped Silica Fiber

First-principles calculations were used to simulate the aggregation of the peroxy chain defect POL and the oxygen vacancy defect ODC(I). Defect aggregation's electronic structure and optical properties were investigated. The two defects were most likely to accumulate on a 6-membered ring in ortho-position. When the two defects are aggregated, it is discovered that 0.75 ev absorption peaks appear in the near-infrared band, which may be brought on by the addition of oxygen vacancy defect ODC(I). We can draw the conclusion that the absorption peak of the aggregation defect of ODC(I) defect and POL is more prominent in the near infrared region and visible light area than ODC(I) defect and POL defect.

Potential of ytterbium doped silica glass for solid-state optical refrigeration to below 200 K.

We report on the optical refrigeration of ytterbium doped silica glass by >40 K starting at room temperature, which represents more than a two-fold improvement over the previous state-of-the-art. A spectroscopic investigation of the steady-state and time-dependent fluorescence was carried out over the temperature range 80 K to 400 K. The calculated minimum achievable temperature for our Yb3+ doped silica sample is ≈150 K, implying the potential for utilizing ytterbium doped silica for solid-state optical refrigeration below temperatures commonly achieved by standard Peltier devices.

Dual fluorescent hollow silica nanofibers for in situ pH monitoring using an optical fiber.

This study reports a sensitive and robust pH sensor based on dual fluorescent doped hollow silica nanofibers (hSNFs) for in situ and real-time pH monitoring. Fluorescein isothiocyanate (FITC) and tris(2,2'-bipyridyl)dichlororuthenium(ii) hexahydrate (Ru(BPY)3) were chosen as a pH sensitive dye and reference dye, respectively. hSNFs were synthesized using a two-step method in a reverse micelle system and were shown to have an average length of 6.20 μm and average diameter of 410 nm. The peak intensity ratio of FITC/Ru(BPY)3 was used to calibrate to solution pH changes. An optical-fiber-based fluorescence detection system was developed that enabled feasible and highly efficient near-field fluorescence detection. The developed system enables fully automated fluorescence detection, where components including the light source, detector, and data acquisition unit are all controlled by a computer. The results show that the developed pH sensor works in a linear range of pH 4.0-9.0 with a fast response time of less than 10 s and minimal sample volume of 50 μL, and can be stored under dark conditions for one month without failure. In addition, the as-prepared hSNF-based pH sensors also have excellent long-term durability. Experimental results from ratiometric sensing confirm the high feasibility, accuracy, stability and simplicity of the dual fluorescent hSNF sensors for the detection of pH in real samples.

Multi-mode step graded index fibers performance parameters (attenuation/dispersion/mode field) measurements by using OptiFiber simulation

Abstract This paper has clarified the positive and negative effects of 3.1% germania and 1% fluorine DS fibers in multi-mode silica profile. The group delay and the total fiber dispersion against operating wavelength for PS and various doped silica (DS) fibers are demonstrated and assured by using OptiFiber simulation. The material, waveguide and total fiber dispersions are demonstrated against wavelength for the PS fiber, 3.1% germania DS (GDS) fiber and 1% fluorine DS (FDS) fiber. Besides the mode field diameter, fiber material loss, fiber bending loss and the dispersion group delay are simulated and clarified against the operating wavelength for PS and different DS fibers. The study gives the effects of the dopant ratio of germania and fluorine on the zero dispersion wavelength shift and DS.

Thermoluminescence kinetic parameters of proton-irradiated germanium doped flat-shape optical fibres

Glow curve is a key element in thermoluminescence (TL) studies as it provides on-the-ground understanding on the trapping mechanism inside the crystal lattice and hence stability of the TL material. In the present work, luminescence mechanism of the in-house fabricated germanium doped (Ge-doped) flat-shape silica optical fibres have been investigated following irradiation by 150-MeV proton beams. Results of TL dose-response showed that there is a linear relationship between TL response and proton doses from 1 to 10 Gy, with a coefficient of determination close to one. The structure of glow curve remains unchanged throughout the studied dose range with a maximum glow peak dominated at temperature of within 250–290 °C. A Tmax-Tstop plot reveals not only horizontal regions but also smooth slopes, indicative of the presence of a continuum distribution of glow peaks and trap depth. A computerised glow curve deconvolution analysis of the respective fibre glow-curves demonstrated that they were composed of five strongly overlapping peaks underlying a broad TL spectrum, obtaining figures of merit in the range of 0.56–1.64%. The main physical kinetic parameters (activation energy and frequency factor) of the fitted glow peaks were obtained using GlowFit software. The data suggest that the TL glow peaks of the Ge-doped silica optical fibres obey second-order kinetics.

Representation of the Characteristic Temperature of Correlative Thermal Conductivity of Opacifier-Fiber Doped Silica Aerogel by Steady-State Method at Large Temperature Differences

Representation of the Characteristic Temperature of Correlative Thermal Conductivity of Opacifier-Fiber Doped Silica Aerogel by Steady-State Method at Large Temperature Differences

Co-Doping Effect of Bismuth Ions on the Gain Characteristics of Er-Doped Silica Optical Fiber

By examining the spectral and amplification characteristics of Er-doped silica fiber (EDSF) and Bi/Er co-doped silica fiber (BEDSF), an active doped silica fiber with broadband- and flat-gain is investigated. Results show that the bandwidth of BEDSF with a gain greater than 20 dB is approximately 50 nm. Moreover, in the entire C-band, the gain of BEDSF exceeds 26 dB with a fluctuation range of approximately 2 dB. The excellent performance may mainly come from the role of bismuth ions. Further analysis demonstrates that the emission and gain cross-sections are enhanced, the bandwidth is broadened, and the flatness is also optimized by co-doping Bi ions. The fluorescence lifetime of Er3+ is lengthened by 1.82 ms, illustrating that there may exist energy transfer from Bi-related active centers to Er3+. The results indicate that the proposed BEDSF has significant potential application in optical fiber amplifiers, lasers, sensors, and so on.

Second-harmonic generation in a high-index doped silica micro-ring resonator.

We report the first, to the best of our knowledge, observation of second-harmonic generation (SHG) in a high-index doped silica micro-ring resonator, due to the symmetry-breaking-induced χ(2) at the core and cladding interface of the waveguide. The generated SH power is shown to have quadratic dependence on the in-cavity power of the fundamental pump at around 1550 nm. The pumping wavelength sweep method is adopted to fulfill the phase-matching condition for maximum conversion efficiency of SHG. This work offers a new approach to generate a visible source for the visible-light integrated optical platform from infrared-visible light conversion.

A review of micro silica beads in radiation dosimetry applications

A recent development in the field of radiation measurement is the use of silica glass beads as high performance thermoluminescent detectors. The application of using doped silica glass jewellery beads as radiation detectors was first proposed by Jafari in 2014, on the basis that it held the potential to resolve long standing issues in dosimetry, could be cheaply implemented, and had yielded good results in initial experimental work. Today the body of literature concerned with glass bead dosimeters has grown extensively, covering their behaviour in various radiation fields, as well as their handling and storage properties. The purpose of this review is to summarise the results obtained in the literature so far. Paramount among these is the finding that beads could offer excellent performance in radiotherapy applications, particularly due to their small volume (1–3 mm3), measurement reproducibility of less than 3% (k = 2), chemical inertness and low fading rate (10% over the first 30 days after irradiation). The beads are energy independent over the MV photon and MeV electron energy ranges and exhibit good linearity in electron, proton, carbon ion and photon radiation (an R2 of 0.999 having been achieved from 1 cGy to 50 Gy in a 6 MV photon beam) as well as being dose-rate and angular independent. However, significant energy dependence in the lower energy range is apparent (<300 kV), thus careful calibration is required. Irradiation of beads with neutrons has also been studied, the reported results indicate their potential use as high spatial resolution alternatives to the gas detectors presently used in industrial and scientific fields. Published use cases of silica beads have been identified and summarised in this review, these include treatment plan verification, small field dosimetry, SABR audits and kV therapy all of which demonstrating the potential use for silica bead TLDs within Radiotherapy.

CO2 reforming of CH4 over Ni supported on SiO2 modified by TiO2 and ZrO2: Effect of the support synthesis procedure

Two series of catalysts containing nickel supported on silica modified by TiO2 and ZrO2 were tested in the dry (CO2) reforming of methane (DRM). The two series of catalysts with 10 wt% Ni and with Ti(Zr)/Si = 1 were obtained by using two different support preparation procedures. One series had the support synthesized by sol-gel and the other series the support obtained by grafting a home-made SiO2 with zirconium and titanium alkoxides. According to XRD, TPR, NH3 -TPD and XPS analyses, the two series of catalysts and supports had different structural, acidic, and surface chemistry properties. The promoter effect was evaluated with respect to the nickel supported on bare silica. DRM reaction was conducted in a fixed-bed reactor at atmospheric pressure in the low temperature range of 450–650 °C with a feed gas mixture containing CH4 and CO2 in a 1:1 ratio in He. As compared to the unpromoted nickel catalyst, doping silica with titanium oxide increased the methane conversion in the entire range of the tested temperature, and the catalytic stability at 650 °C during 24 h of time on stream. The effect was quite remarkable in the case of the nickel on the sol-gel prepared support exhibiting at 650 °C a stable 65 % CH4 conversion during 24 h. On the contrary, regardless the support preparation method, the presence of zirconium affected only slightly the methane conversion and the catalytic stability. After catalytic test, all the catalysts formed carbon but to a less extent the ones with the grafted supports. The structural characterizations before and after the reaction confirmed a better structural stability of the nickel particles supported on the sol-gel doped silica, explaining the improvement of the catalytic stability during the DRM reaction.

Effects of P co-doping on X-ray/450 nm LD induced photodarkening in Dy3+ doped silica glass and fiber laser

Effects of P-codoping on X-ray/450 nm LD induced photodarkening in Dy3+ doped silica glass and fiber were investigated to develop a visible fiber laser. P and Dy concentrations in Dy-P-doped silica glass were optimized to reduce Rayleigh scattering. It was found in optimized glass that X-ray-induced photodarkening can be well suppressed by P co-doping. 450 nm LD pumped laser oscillation was firstly observed in the fiber using optimized glass. The slope efficiency is 4.2% which is lower than those in Dy–Al-and Dy–Al–Ge-doped fibers previously reported. Contrary to the results of X-ray-induced PD, 450 nm LD-induced photodarkening easily occurred.

Nanocrystalline Yb:YAG-Doped Silica Glass with Good Transmittance and Significant Spectral Performance Enhancements.

In this study, Yb:YAG-nanocrystal-doped silica glass with high transmission and excellent spectral properties was successfully prepared using a modified sol–gel method. The X-ray diffraction (XRD), micro-Raman spectroscopy, electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM) analyses confirmed that the Yb:YAG nanocrystals, with their low content, homogeneous distribution, and small crystal size, directly crystallized into the silica glass network without annealing treatment. In contrast with conventional microcrystalline glass having large particles (>0.1 μm) and a large particle content, nanocrystalline glass with a homogeneous distribution and sizes of ~22 nm had higher optical transmittance and better spectral properties. Compared with Yb3+ doped silica glass without nanocrystals, the Yb:YAG-nanocrystal-doped silica glass had a 28% increase in absorption cross-section at 975 nm and a 172% enhanced emission cross-section at 1030 nm without any changes in the spectral pattern of the Yb3+ ions in the silica glass. Meanwhile, the Yb:YAG-doped silica glass with large size and high optical quality was easily prepared. Therefore, the Yb:YAG-nanocrystal-doped silica glass is expected to be a promising near-infrared laser material.

Effect of Al3+ on the photoluminescence and radioluminescence properties of Mn2+-Doped high silica glass

Mn2+/Al3+-, Eu2+/Mn2+-, and Eu2+/Mn2+/Al3+-doped high silica glasses were prepared to investigate their photoluminescence and radioluminescence properties. Particularly, the effect of Al3+ on the energy transfer from Eu2+ to Mn2+ and the regulation law of Mn2+ luminescence properties in Mn2+/Al3+- and Eu2+/Mn2+/Al3+-doped glasses were investigated. A strategy to improve the radioluminescence intensity of glasses was developed, and the radioluminescence intensity formula was improved. The dispersion caused by Al3+ improves the luminous intensity of Mn2+ and lowers the efficiency of the Eu2+→Mn2+ energy transfer in high silica glass. Al3+ can significantly broaden the excitation spectrum of Mn2+ by affecting the coordination number of Mn2+ and changing the field intensity around Mn2+ ions. Notably, the developed glass can potentially be applied in laser and LED lights. In addition, nonbridging oxygens (NBOs) are considered to be the main factor leading to the low efficiency of glass radioluminescence. Al3+ is able to reduce the relative amount of NBOs by forming [AlO4/2]−1 tetrahedra, thereby improving the radioluminescence intensity effectively.

Radiation‐induced darkening and its suppression methods in Yb3+‐doped silica fiber core glasses

AbstractYb3+‐doped silica fiber (YDF) laser has important applications in space. However, the darkening effect caused by space ionizing radiation (called RD effect), which is due to the generation of color centers at the microscopic scale, can significantly deteriorate the performance of the YDF laser. This review mainly includes three aspects. First, we briefly introduce space radiation environment and challenges that optical fibers encounter in space. Second, we review the nature and generation mechanism of color centers responsible for RD in YDFs. Finally, we systematically introduce five methods to inhibit RD and their inhibition mechanisms.

Representation of the Characteristic Temperature of Correlative Thermal Conductivity of Opacifier-Fiber Doped Silica Aerogel By Steady-State Method at Large Temperature Differences

Representation of the Characteristic Temperature of Correlative Thermal Conductivity of Opacifier-Fiber Doped Silica Aerogel By Steady-State Method at Large Temperature Differences