Lithium ion conduction in lithium metaphosphate based systems

A comparative investigation on Li⁺ ion transport has been carried out in various phases of lithium metaphosphate such as (i) crystalline LiPO₃, (ii) glassy form as mol % 50Li₂O-50P₂O₅, synthesized by melt-quenching process, (iii) single phase glass-ceramic LiPO₃ obtained through controlled heat treatment of mol % 50Li₂O-50P₂O₅ and (iv) newly identified polymer-metal salt complex (PEO)₆: LiPO₃. All of the above materials have been characterized through XRD, DSC, optical microscopy and impedance spectroscopy techniques. The Li⁺ ions, migrating with an activation energy value of 1.4 eV through “interstitial mechanism” in polycrystalline LiPO₃, exhibited a dc conductivity value of 2.5×10^-8 Scm^-1 at 280 °C. The above conductivity value was enhanced by four orders of magnitude in Li₂O-P₂O₅ glass, with an activation energy value of 0.72 eV. The glass subjected to controlled heat treatment devitrified into single phase glass-ceramic, as revealed by XRD and optical microscopy studies. The glass-ceramic exhibited better conduction characteristics compared to polycrystalline LiPO₃. Polycrystalline LiPO₃, complexed with polymer PEO has exhibited a conductivity value of 3.1×10^-7 Scm^-1 at 78 °C with activation energies of 0.21 and 0.88 eV for Li⁺ ion migration above and below the softening point of the polymer, respectively. PACS 66.10.Ed; 71.55.Jv; 81.30.Hd; 82.45.Gj; 82.45.Wx     

Optical amplification of Eu(DBM)3Phen-doped polymer optical fiber

A preform technique is used to prepare a step-index (SI) polymer optical fiber (POF) doped with Eu(DBM)3Phen. The gain (5.7 dB) at 613 nm of the doped SI POF with Eu3+ content of 4000 in 10(6) wt., 0.4-mm core diameter, and 30-cm fiber length is observed at ambient temperature by end pumping with a YAG at 355 nm. The input signal light is approximately 0.2 W. The results show the possibility of signal gain in a rare-earth-doped POF amplifier and the potential of a polymer doped with rare-earth ions as an active optical device.     

Clustering study in Eu(DBM)3Phen-doped polymer optical fibers by optical properties and near-field scanning microscopy

The clusters of Eu3+ ion in Eu(DBM)3Phen-doped polymethyl methacrylate (PMMA) have been studied by three means. The relative fluorescence intensity ratio of the 5D0 → 7F2 to 5D0 → 7F1 transitions with different concentrations of Eu3+ in Eu(DBM)3Phen-doped PMMA and metastable-state (5D0) lifetime dependence on Eu3+ concentration are analyzed. The analysis indicates that there are no clustering effects in Eu3+ ions of Eu(DBM)3Phen-doped PMMA when the Eu3+ doping concentration is up to 1.0 wt.-%. At the same time, the clustering effect has not been observed by the scanning near-field optical microscopy (SNOM) in Eu(DBM)3Phen-doped PMMA with 1.0 wt.-% of Eu3+ ions. The analysis reveals that a high concentration of Eu3+ can be incorporated into polymer optical fiber (POF) without clustering effect.OCIS codes: 180.5810, 300.6280, 250.5460, 160.5690.     

Subluminal and superluminal propagation in Er<Superscript>3+</Superscript> doped fiber Bragg grating

The method to pump the FBG written into an Er³⁺-doped optical fiber is proposed to decrease or increase the group velocity of a probing pulse based on the fact that a pump-induced process changes the refractive index and dispersion associated with the ⁴I_15/2-⁴I_13/2 transition in Er³⁺-doped optical fiber. The system equations are derived. The group velocity modification is numerically demonstrated and discussed with the effects of an optical pump power, fiber Bragg grating length, doping concentration of Er³⁺ ions, and modulation amplitude of the grating.     

Optical properties of transparent cobalt-containing magnesium aluminosilicate glass-ceramics doped with gallium oxide for saturable absorbers

Transparent glass-ceramic materials based on glasses of the MgO–Al₂O₃–SiO₂–TiO₂ system doped with CoO and Ga₂O₃ are synthesized. The secondary heat treatment of the initial glasses at temperatures of 800–950°C leads to precipitation of nanosized (6–7 nm) crystals of magnesium aluminogallium spinel doped with cobalt ions and magnesium aluminotitanate solid solutions. The optical absorption spectra of the initial glass and glass-ceramic materials are studied. It is shown that the absorption band caused by the ⁴A₂(⁴F)→ ⁴T₁(⁴F) transitions of tetrahedrally coordinated Co²⁺ ions in glass-ceramics with nanosized Co:Mg(Al,Ga)₂O₄ crystals is shifted to longer wavelengths (up to ~1.67 µm) compared to the position of this band in materials with Co:MgAl₂O₄ crystals. The synthesized glass-ceramics are characterized by a relatively low saturation fluence FS ~ 0.5 ± 0.1 J/cm² at a wavelength of 1.54 µm, as well as by a high radiation resistance to nanosecond laser pulses, which is no lower than ~15 ± 2 J/cm². This explains their attractiveness as materials for saturable absorbers for erbium lasers emitting in the spectral range 1.5–1.7 µm.     

Experimental comparison of a Kerr nonlinearity figure of merit including the stimulated Brillouin scattering threshold for state-of-the-art nonlinear optical fibers

We introduce a new figure of merit (FOM) including the input pump power limit associated with stimulated Brillouin scattering (SBS) for evaluation of the Kerr nonlinearity efficiency of optical fibers. The new FOM is expressed as gammaL(eff)P(SBS) (gamma is a nonlinearity parameter, L(eff) is effective length, and P(SBS) is the SBS threshold), while the conventional FOM is given by gammaL(eff). Using the new FOM, we perform an efficiency comparison among four types of state-of-the-art nonlinear optical fiber: a Bi2O3-based nonlinear fiber, a silica-based holey fiber, a highly nonlinear dispersion-shifted fiber, and a conventional dispersion-shifted fiber. The Bi2O3-based nonlinear fiber is found to have the best Kerr nonlinearity efficiency owing to the superior nonlinear property of the Bi2O3 glass compared with that of the silica.     

Development of X-ray storage phosphor glass-ceramics

Europium- and bromine-doped fluorozirconate glass-ceramics show a significant photostimulated luminescence (PSL) effect after X-irradiation at room temperature. The PSL is assigned to the 5 d -4 f emission of Eu 2+ ions incorporated in barium bromide crystallites which are formed in the glass matrix upon suitable thermal annealing. The BaBr 2 crystallites grows in both the hexagonal and orthorhombic phases. The PSL efficiency of the glass-ceramic containing predominantly the hexagonal phase is only about 0.0025% of the well-known crystalline storage phosphor BaFBr:Eu used as a standard, whereas the glass-ceramic containing the orthorhombic phase has a relative efficiency of a few percent. Using the same formulation for the fluorozirconate glass-ceramic, but replacing Na by Rb and Li, results in the formation of RbBa 2 Br 5 microcrystallites after suitable annealing. The relative PSL efficiency increases to about 10%. The structural changes in these two fluorozirconate glass-ceramics were monitored by X-ray diffraction, photoluminescence, and electron paramagnetic resonance.     

Are low-loss glass ceramic optical waveguides possible?

The results of a cutback measurement of a glass-ceramic optical waveguide with single-mode fiber geometry have demonstrated that sub decibels per kilometer losses can be achieved. Difference spectra show that the limit of intrinsic scattering in these two-phase structures ought to be tens of decibels per kilometer.     

Grain size effects on dynamics of Li-ions in Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> glass-ceramic nanocomposites

Li₃V₂(PO₄)₃ glass-ceramic nanocomposites, based on 37.5Li₂O-25V₂O₅-37.5P₂O₅ mol% glass, were successfully prepared via heat treatment (HT) process. The structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns exhibit the formation of Li₃V₂(PO₄)₃ NASICON type with monoclinic structure. The grain sizes were found to be in the range 32–56 nm. The effect of grain size on the dynamics of Li⁺ ions in these glass-ceramic nanocomposites has been studied in the frequency range of 20 Hz–1 MHz and in the temperature range of 333–373 K and analyzed by using both the conductivity and modulus formalisms. The frequency exponent obtained from the power law decreases with the increase of temperature, suggesting a weaker correlation among the Li⁺ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. The imaginary modulus spectra are broader than the Debye peak-width, but are asymmetric and distorted toward the high frequency region of the maxima. The electric modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent β is fairly low, suggesting a higher ionic conductivity in the glass and its glass-ceramic nanocomposites. The advantages of these glass-ceramic nanocomposites as cathode materials in Li-ion batteries are shortened diffusion paths for Li⁺ ions/electrons and higher surface area of contact between cathode and electrolyte.     

氟氧化物玻璃陶瓷中高效低阈值的红色上转换发光现象

本文报道了一种Er3 + 和Tm3 + 共掺杂新的氟氧化物玻璃陶瓷材料中高效低阈值的红色上转换发光现象。材料组份为 6 5GeO2 2 5NaF 8 5BaF 0 5Tm2 O3 1Er2 O3 (mol% ) ,文中给出了样品的制备方法。在 978nmLD激发下 ,观察到了非常强的红色上转换发光。据我们所知 ,在如此低的Er3 + 和Tm3 + 掺杂浓度下实现了如此之强的红色上转换发光 ,文献中未见报道 ;更令人惊奇的是在 2 0 0mA工作电流 (此时功率为 3 5mW )LD激发下 ,激发的功率密度为 170mW·cm-2 ,其红色光仍裸眼可见。讨论了这种高效低阈值上转换发光的机理。研究了LD的工作电流与上转换发光强度的关系     

Optimization of the dimensions of an Yb(3+):ZBLANP optical fiber sample for laser cooling of solids

We propose a theoretical model for an optimized fiber structure for use in anti-Stokes laser cooling of solids. The sample is an optical fiber fabricated from a fluorozirconate glass ZBLANP with a core doped with Yb(3+) ions. The diameter of the fiber core is optimized to achieve the largest temperature change in the sample. It is shown that for each value of the pump power there is an optimized diameter of the fiber core, which permits the largest drop in the temperature of the sample.     

Evanescent-wave optical Cr VI sensor with a flexible fused-silica capillary as a transducer

A light-guiding, flexible fused-silica (FFS) capillary has been used in designing an optical fiber Cr VI sensor for monitoring Cr VI ions in water samples. The FFS capillary is similar to a conventional silica optical fiber in that it can guide light in the wavelength region from the UV to the near IR but different from a conventional optical fiber in that it is a tubular waveguide. The inner surface of the FFS capillary is fused silica, which one can modify to design an optical fiber chemical sensor. The FFS capillary has a cladding layer plus a protective polymer coating on its outside surface. The cladding layer ensures the ability of the FFS capillary to guide light. The protective coating increases the FFS capillary's mechanical strength and makes it robust for practical applications. Compared with conventional silica optical fibers, it is much easier and more feasible to use this FFS capillary to fabricate long-path (tens of meters to thousands of meters) evanescent-wave based chemical sensors. We describe a Cr VI sensor based on the intrinsic evanescent-wave absorption by Cr VI ions in a water sample filled inside the capillary as an example of use of a FFS capillary in chemical sensor design. This simple sensor, using a 30 m light-guiding FFS capillary as a transducer, has the capability of detecting as little as 31 parts in 10(9) of Cr VI in a water sample, which is close to the detection limit of some sophisticated, expensive analytical instruments.     

The effect of Erbium concentration on the optical spectrum of Erbium-doped fiber laser

We report an experimental observation of the influence of concentration of Er³⁺ ions in an Erbiumdoped silica fiber on the spectral characteristics of an erbium fiber laser. Our basic conclusion is that an increase of erbium concentration in the fiber results in the laser optical spectrum narrowing. We also discuss possible mechanisms responsible for this effect.     

Nonmonotonic saturation characteristic and excited state absorption in long optical fiber

A sort of nontrivial competition between the excited state absorption (ESA) and optical gain is shown and interpreted for 9 m-long optical fiber. Using a typical SiO₂:Nd³⁺ fiber we observe an interesting nonmonotonic dependence of the gain on signal (probe beam) intensity with substantial contribution of the ESA. This behavior is simulated via kinetic analysis.     

Li_2O-Al_2O_3-SiO_2-P_2O_5系统微晶玻璃受控析晶分析

应用DTA,XRD,SEM等手段研究了Li2O_Al2O3_SiO2_P2O5系统微晶玻璃的析晶过程和相组成。采用模拟计算方法考察了不同的析晶条件。引入适量的Al2O3等难熔物组分来改变析晶条件及残留玻璃相的组成和粘度。通过抑制主晶相(Li2O.2SiO2)晶粒的生长,最终获得了晶粒尺寸为0.1~0.3μm的透明微晶玻璃。     

Submicrometer organic silica gel fiber for oxygen sensing

We introduce the electrospinning method into fabricating oxygen-sensitive submicrometer scale optical fiber. Uniform tris (4,7-diphenyl-1,10-phenathroline) ruthenium(II) dichloride ([Ru(dpp)(3)](2+)Cl(2))-doped fibers with a diameter of 900 nm are obtained by electrospinning the organic silicon sol solution derived from tetraethyl orthosilicate and n-Octyltriethoxysilane (C(14)H(32)O(3)Si). The experimental results show that the single gel fiber exhibits excellent optical and sensing properties. A laser with a wavelength of 452 nm can be efficiently launched into the fiber and guide along the fiber to excite the fluorescence. Then, we find that [Ru(dpp)(3)](2+)-gel fiber has favorable optical and sensing characteristics, and the Stern-Volmer plots are linear in the full concentration range of O(2) (0-100 vol.?%). The ratio of I(0)/I(100), where I(0) and I(100) respectively represent the fluorescence intensities of the fiber exposed to 100% N(2) and 100% O(2), as the sensitivity of the fiber is 3.5. Simultaneously, the fiber can make a quick response within 100 ms. This method provides an effective and convenient way to fabricate highly uniform nanoscale or microscale optical waveguides for photonic devices.     

Optical signal processing using nonlinear fibers

Ultra-fast optical signal processing is a promising technology for future photonic networks. This paper describes possible applications of nonlinear fibers to optical signal processing. The third-order optical nonlinearities in a fiber are discussed by analyzing the interaction of co-propagating optical waves. The properties of a nonlinear fiber are then considered in terms of optimizing the dispersion for achieving phase matching and decreasing walk-off. A highly nonlinear fiber (HNLF) is a practical candidate for an ultra-high-speed signal processor. Using HNLF, the following experiments are successfully demonstated: ultra-broadband wavelength conversion/optical phase conjugation by four-wave mixing, 160 Gb/s optical 3R-regeneration, and optical switching up to 640 Gb/s using a parametric amplified fiber switch. Steps for further improvements are also discussed.     

High-frequency (94.9 GHz) EPR spectroscopy of paramagnetic centers in a neutron-irradiated sapphire single-crystal fiber

Initial results are reported of an EPR study, conducted at 94.9 GHz, of a thermally annealed, neutron-irradiated white sapphire (α-Al₂O₃) single-crystal fiber. The optical centers produced in sapphire by neutron irradiation and thermal annealing are of interest for optical technologies involving the phenomenon of spectral hole-burning. While these centers have been modeled as consisting of electrons localized at anion vacancies, experimental tests of this model have been very limited. EPR spectroscopy — a choice technique for elucidating structural details of such color centers — reveals signals from numerous paramagnetic centers in this material. The predominant signals, with amplitudes a hundredfold greater than any other signals, derive from three closely related, highspin-multiplicity centers. These centers do not, however, derive from radiation-induced lattice defects: they are readily identified as Cr³⁺ (S = 3/2) and a pair of crystallographically equivalent Fe³⁺ (S=5/2) impurity ions. The advantages of high-frequency-EPR instrumentation in facilitating this identification are presented and discussed in detail. These advantages include enhanced sensitivity for this volume-limited, fiber sample. Moreover, the analysis of the spectra — entailing spectral assignments, evaluation of the spin-Hamiltonian parameters, and spin-counting — is greatly facilitated when the Zeeman interaction is dominant.     

伽马辐照对掺镱光纤材料特性影响的研究

掺镱光纤是高功率激光器的核心材料,但在高能射线辐照后其应用性能会显著下降,因此有必要对掺镱光纤材料在辐照环境下的性能变化进行深入研究。采用改进型化学气相沉积法结合稀土螯合物掺杂制备了系列光纤预制棒及光纤,测试了光纤在不同剂量下射线辐照前后的高功率输出性能,以及光纤预制棒辐照前后的吸收光谱及镱离子荧光寿命。结果表明:小剂量辐照后掺镱光纤的高功率输出显著下降,通过预制棒吸收光谱可看出主要是因为伽马辐照后使掺镱光纤材料中Al的相关缺陷浓度增多,在可见光区域吸收损耗增加。Ce离子的掺杂通过缓减辐致铝氧空位中心(Al-OHC)色心缺陷的增加,减少Yb离子荧光寿命的下降,可在一定程度上抑制高功率掺镱光纤的辐致暗化。     

Preparation and characterization of Sr_(0.5)Ba_(0.5)Nb_2O_6 glass-ceramic on piezoelectric properties

We studied the influence of heat treatment time on the optical, thermal, electrical, and mechanical properties of strontium barium niobate(Sr_(1-x)Ba_xNb_2O_6; hereafter SBN) piezoelectric glass-ceramics with tungsten bronze-type structure,which have good piezoelectric properties and are important lead-free piezoelectric materials. We found that the best heat treatment time is 4 h. The properties of the prepared materials are better than that of SBN ceramics and the glass-ceramic growth is faster than the SBN crystal when the heat treatment time of the SBN piezoelectric glass-ceramic is controlled,reducing the preparation costs greatly.