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Preparation and MIR Luminescence Properties of Er<sup>3+</sup> Doped Fluorochloride Glass
Nd³⁺/Yb³⁺ co-doped fluorobromide glass sample was prepared by melt quenching. The MIR luminescence of the Nd³⁺/Yb³⁺ co-doped fluorobromide glass was investigated by Br-doping reduces the phonon state density of the matrix. The 3.9 μm MIR luminescence of the samples excited at 793 and 980 nm pump excitation were investigated in detail. There is an effective mutual energy transfer process between Nd³⁺ and Yb³⁺. It is proved under 793 nm excitation that the luminescence of Nd³⁺ at 3.9 μm is reduced by effective energy transfer from Nd³⁺:²H11/2 → Yb³⁺:²F5/2. At the same time, it is proved that the effective energy transfer from Yb³⁺:²F5/2 → Nd³⁺:²H11/2 under the excitation of 980 nm enhanced the light luminescence of Nd³⁺ at 3.9 μm. In addition, it is found that the samples still have good IR luminescent properties when the temperature changes. The luminescence cross-sectional area and the absorption cross-sectional area are σem (3.87×10–20 cm²) and σabs (4.25×10–20 cm²). The fluorescence decay characteristics of the sample at 3.9 μm at the ²H11/2 level were investigated and the fluorescence lifetime was calculated. The gain performance of the sample was calculated and analyzed, which can reach 4.25×10–20 cm². Those results prove that Nd³⁺/Yb³⁺ co-doped fluorobromide glass is the potential mid-infrared laser gain material.
Ho³⁺ doped ZBLAN glass with 2.0 and 2.9 μm emission has been prepared. In order to further improve the luminescence of Ho³⁺, halogen ions (Cl, Br, I) are introduced to reduce the maximum phonon energy and phonon state density of the sample. At the same time, Nd³⁺ is introduced to transfer the energy to Ho³⁺ pumped with a 793 nm laser(Nd³⁺:⁴F5/2,⁴F3/2→Ho³⁺:⁵I6). The effect of different halogen ion on the luminescent properties of the fluoride halide glass is compared. The results show that the luminescent intensity of infrared increases with the introduction of different halogen ions. By comparison, it is found that the sample with I– has the strongest luminescence of 1064 nm, 2.0 μm and 2.9 μm. This is consistent with the calculated J-O intensity parameters. In addition, the 2.0 and 2.9 μm emission of Ho³⁺ pumped with a 450 nm laser will not disappear. A mid-infrared sample with multi-wavelength excitation and multi-wavelength emission can be obtained. Nd³⁺/Ho³⁺ co-doped fluoride halide glass with 1064 nm, 2.0 μm and 2.9 μm luminescence were prepared by melt quenching method. The luminescent mechanism and the energy transfer process between the two ions of Nd³⁺/Ho³⁺ co-doped fluoride halide glass are studied. The J-O parameters, luminescence lifetime and absorption emission cross-sectional area of Ho³⁺ and Nd³⁺ are calculated, respectively. It is found that the value of Ω2 in the glass matrix increased with the introduction of different halogen ions, while Ω4 and Ω6 did not change obviously in different glass composition. This is because the environment of the crystal field around the rare earth ions has changed. The crystal phase and phonon energy of the sample are analyzed by X-ray diffraction pattern and Fourier transform infrared spectrometer, respectively. Based on the above spectra and data (phonon energy is 634.71 cm–1), it can be predicted that Nd³⁺/Ho³⁺ co-doped fluoride halide glass is a potential mid-infrared luminescent material.
Er3+-doped transparent glass ceramics containing micron-sized SrF2 crystals were obtained by direct liquid-phase sintering of a mixture of SrF2 powders and precursor glass powders at 820 °C for 15 min. The appearance and microstructural evolution of the SrF2 crystals in the resulting glass ceramics were investigated using X-ray diffraction, field-emission scanning electron microscopy and transmission microscopy. The SrF2 crystals are ~15 μm in size and are uniformly distributed throughout the fluorophosphate glass matrix. The glass ceramics achieve an average transmittance of 75% in the visible region and more than 85% in the near-IR region. The high transmittance of the glass ceramics results from matching the refractive index of the SrF2 with that of the precursor glass. Energy dispersive spectroscopy, photoluminescence spectra, and photoluminescence lifetimes verified the incorporation of Er3+ into the micron-sized SrF2 crystals. Intense 2.7 μm emissions due to the 4I11/2 → 4I13/2 transition were observed upon excitation at 980 nm using a laser diode. The maximum value of the emission cross section of Er3+ around 2.7 μm is more than 1.2 × 10−20 cm2, which indicates the potential of using transparent glass ceramics containing micron-sized SrF2 crystals for efficient 2.7 μm lasers and amplifiers.
A number of dielectric materials have been employed for on-chip frequency comb generation. Silicon based dielectrics such as silicon dioxide (SiO2) and silicon nitride (SiN) are particularly attractive comb materials due to their low optical loss and maturity in nanofabrication. They offer third-order Kerr nonlinearity (χ(3)), but little second-order Pockels (χ(2)) effect. Materials possessing both strong χ(2) and χ(3) are desired to enable self-referenced frequency combs and active control of comb generation. In this review, we introduce another CMOS-compatible comb material, aluminum nitride (AlN),which offers both second and third order nonlinearities. A review of the advantages of AlN as linear and nonlinear optical material will be provided, and fabrication techniques of low loss AlN waveguides from the visible to infrared (IR) region will be discussed.We will then show the frequency comb generation including IR, red, and green combs in high-Q AlN micro-rings from single CW IR laser input via combination of Kerr and Pockels nonlinearity. Finally, the fast speed on-off switching of frequency comb using the Pockels effect of AlN will be shown,which further enriches the applications of the frequency comb.
Silicon and graphene are promising anode materials for lithium-ion batteries because of their high theoretical capacity; however, low volumetric energy density, poor efficiency and instability in high loading electrodes limit their practical application. Here we report a large area (approximately 15 cm × 2.5 cm) self-standing anode material consisting of molecular precursor-derived silicon oxycarbide glass particles embedded in a chemically-modified reduced graphene oxide matrix. The porous reduced graphene oxide matrix serves as an effective electron conductor and current collector with a stable mechanical structure, and the amorphous silicon oxycarbide particles cycle lithium-ions with high Coulombic efficiency. The paper electrode (mass loading of 2 mg cm-2) delivers a charge capacity of ~4588 mAh g-1electrode (~4393 mAh cm-3electrode) at 1,020th cycle and shows no evidence of mechanical failure. Elimination of inactive ingredients such as metal current collector and polymeric binder reduces the total electrode weight and may provide the means to produce efficient lightweight batteries.
Mid-infrared ultrafast fiber lasers are valuable for various applications, including chemical and biomedical sensing, material processing and military applications. Here, we report all-fiber high-power graphene mode-locked Tm/Ho co-doped fiber laser at long wavelength with evanescent field interaction. Ultrafast pulses up to 7.8 MHz are generated at a center wavelength of 1879.4 nm, with a pulse width of 4.7 ps. A graphene absorber integrated with a side-polished fiber can increase the damage threshold significantly. Harmonics mode-locking can be obtained till to the 21(th) harmonics at a pump power of above 500 mW. By using one stage amplifier in the anomalous dispersion regime, the laser can be amplified up to 450 mW and the narrowest pulse duration of 1.4 ps can be obtained simultaneously. Our work paves the way to graphene Tm/Ho co-doped mode-locked all-fiber master oscillator power amplifiers as potentially efficient and economic laser sources for high-power laser applications, such as special material processing and nonlinear optical studies.
Er(3+) activated germanate glasses modified by La2O3 and Y2O3 with good thermal stability were prepared. 2.7 μm fluorescence was observed and corresponding radiative properties were investigated. A detailed discussion of J-O parameters has been carried out based on absorption spectra and Judd-Ofelt theory. The peak emission cross sections of La2O3 and Y2O3 modified germanate glass are (14.3 ± 0.10) × 10(-21) cm(2) and (15.4 ± 0.10) × 10(-21) cm(2), respectively. Non-radiative relaxation rate constants and energy transfer coefficients of (4)I11/2 and (4)I13/2 levels have been obtained and discussed to understand the 2.7 μm fluorescence behavior. Moreover, the energy transfer processes of (4)I11/2 and (4)I13/2 level were quantitatively analyzed according to Dexter's theory and Inokuti-Hirayama model. The theoretical calculations are in good agreement with the observed 2.7 μm fluorescence phenomena. Results demonstrate that the Y2O3 modified germanate glass, which possesses more excellent spectroscopic properties than La2O3 modified germanate glass, might be an attractive candidate for mid-infrared laser.
Er(3+) doped oxyfluoride tellurite glasses have been prepared. Three Judd-Ofelt parameters Ωt (t = 2, 4, 6) and radiative properties are calculated for prepared glasses. Emission characteristics are analyzed and it is found that prepared glasses possess larger calculated predicted spontaneous transition probability (39.97 s(-1)), emission cross section σem (10.18 × 10(-21) cm(2)) and σem × Δλeff (945.32 × 10(-28) cm(3)), corresponding to the 2.7 μm emission of Er(3+): (4)I11/2→ (4)I13/2 transition. The results suggest that the prepared glasses might be appropriate optical material for mid-infrared laser application. Moreover, rate equation analysis which is rarely used in bulk glass has been carried out to explain the relationship between emission intensity and Er(3+) concentration. The calculation results show that with the increment of Er(3+) concentration, the energy transfer up-conversion rate of (4)I13/2 state increases while the rate of (4)I11/2 state reduces, resulting in the change of 2.7 μm emission.
We demonstrate a fully coherent supercontinuum spectrum spanning 500 nm from
a silicon-on-insulator photonic wire waveguide pumped at 1575 nm wavelength. An
excellent agreement with numerical simulations is reported. The simulations
also show that a high level of two-photon absorption can essentially enforce
the coherence of the spectral broadening process irrespective of the pump pulse
duration.
Optical frequency combs represent a revolutionary technology for high
precision spectroscopy due to their narrow linewidths and precise frequency
spacing. Generation of such combs in the mid-infrared (IR) spectral region
(2-20 um) is of great interest due to the presence of a large number of gas
absorption lines in this wavelength regime. Recently, frequency combs have been
demonstrated in the MIR in several platforms, including fiber combs,
mode-locked lasers, optical parametric oscillators, and quantum cascade lasers.
However, these platforms are either relatively bulky or challenging to
integrate on-chip. An alternative approach using parametric mixing in
microresonators is highly promising since the platform is extremely compact and
can operate with relatively low powers. However, material and dispersion
engineering limitations have prevented the realization of a microresonator comb
source past 2.55 um. Although silicon could in principle provide a CMOS
compatible platform for on-chip comb generation deep into the mid-IR, to date,
silicon's linear and nonlinear losses have prevented the realization of a
microresonator-based comb source. Here we overcome these limitations and
realize a broadband frequency comb spanning from 2.1 um to 3.5 um and
demonstrate its viability as a spectroscopic sensing platform. Such a platform
is compact and robust and offers the potential to be versatile and durable for
use outside the laboratory environment for applications such as real-time
monitoring of atmospheric gas conditions.
Laser frequency combs, sources with a spectrum consisting of hundred thousands evenly spaced narrow lines, have an exhilarating potential for new approaches to molecular spectroscopy and sensing in the mid-infrared region. The generation of such broadband coherent sources is presently under active exploration. Technical challenges have slowed down such developments. Identifying a versatile highly nonlinear medium for significantly broadening a mid-infrared comb spectrum remains challenging. Here we take a different approach to spectral broadening of mid-infrared frequency combs and investigate CMOS-compatible highly nonlinear dispersion-engineered silicon nanophotonic waveguides on a silicon-on-insulator chip. We record octave-spanning (1,500-3,300 nm) spectra with a coupled input pulse energy as low as 16 pJ. We demonstrate phase-coherent comb spectra broadened on a room-temperature-operating CMOS-compatible chip.
Supercontinuum from 800 to 2,600 nm has been obtained in a soft glass suspended-core photonic crystal fiber. The fiber has been fabricated using an in-house synthesized, lead-bismuth-galate oxide glass (PBG-08), which has a transmission window from 500 nm to 4,500 nm. Dispersion characteristic has been designed to enable efficient pumping in the anomalous regime, using typical telecommunication wavelengths and influence of discrepancy between design and physical dispersion profile of fiber is discussed. An optical parametric amplifier system seeded with a Ti:Sapphire oscillator has been used as a light source (70 fs pulses with 100 kHz repetition rate). Supercontinuum bandwidth on the mid-infrared side is limited by OH
$^-$
absorption of the glass and presence of second zero-dispersion wavelength in the spectral area of interest. Flatness the spectrum remains under 7 dB from roughly 1,800 nm to about 2,500 nm.
Clusters were produced as a result of argon gas cooling during expansion through a supersonic nozzle. A two-dimensional model was set up in order to calculate gas expansion and partial condensation into clusters. Calculations were validated by experimental measurements using Mach-Zehnder interferometry and Rayleigh scattering, and performed with two types of nozzles (Laval and conical nozzles). These optical diagnostics together with numerical simulations led to the cluster size and density determination with spatial resolution through the gas and cluster jet. Cluster production was observed to be very sensitive to the nozzle geometry. Homogeneous gas and cluster jets were produced and characterized using conical nozzle geometry, with cluster density about 1012per cm3. Due to the fast valve-nozzle connecting geometry, shock waves have been observed at the Laval nozzle throat that strongly affected cluster production on the jet axis. Averaged cluster radius was observed to be easily tunable from 180 to 350 Å by varying the upstream gas pressure P0 from 20 to 60 bars. A different scaling law, versus P0, has been observed for this regime of large cluster, compared to Hagena’s predictions for the small cluster regime.
A novel Er³⁺-doped fluorotellurite titanate glasses with the basic molar composition 75TeO2- 5Nb2O5- 5Bi2O3- 5TiO2- 10PbF2, 75TeO2- 5Nb2O5- 5Bi2O3- 5TiO2- 10PbF2- 10000 ppm Er2O3 and 75TeO2- 5Nb2O5- 5Bi2O3- 5TiO2- 10PbF2- 20000 ppm Er2O3 are explored with respect to possible applications as optical amplifiers. Their thermal and optical features were determined using differential scanning calorimetric (DSC), and UV–Vis–NIR spectroscopy, respectively. The glasses transition temperature Tg, factor against crystallization S, optical energy gap and quantum efficiency were determined. Judd-Oflet parameters Ωt (t = 2, 4, 6), branching ratio, β, fluorescence full width at half maximum (FWHM) of NIR emission, and life time τ, of I13/2 level have been evaluated. The glasses were characterized by a higher values of FWHM of NIR emission at 1.53 μm under excitation by wavelength 980 nm with respect to other glasses system doped by single Er³⁺ions. In the future these glasses can be fabricated as broadband fiber amplifier for the optical communication devices. The glasses studied glasses exhibit green emission under excitation wavelength of 445 nm.
A series of erbium-doped fluoro-bromozirconate glasses modified by various concentrations of Br⁻ was prepared using the melt-quenching method. The mid-infrared fluorescence intensity (2.7 μm) was improved by increasing the content of Br⁻. The differential scanning calorimetry, x-ray diffraction, Fourier-transform infrared spectra, Raman spectra, and mid-infrared luminescence spectra were measured. The decreased phonon density shows that the structural changes due to inserting Br⁻ can enhance the mid-infrared luminescent intensity. From the Judd–Ofelt analysis, it was found that the intensity of Ω2 was enhanced with the introduction of Br− and shows greater asymmetry and stronger covalency. Using the Fuchtbauer–Ladenburg theory and McCumber theory, the emission cross section (2.9 × 10⁻²⁰ cm²) and absorption cross section (1.68 × 10⁻²⁰ cm²) at 2.7 μm were determined. Hence, erbium-doped fluoro-bromozirconate glass is a potential material for application in the mid-infrared region.
Eu-doped calcium aluminosilicate glass and glass-ceramic were synthesized and studied by site-selective spectroscopy. Using both broadband excitation and fluorescence line narrowing techniques, the $^5$D$_0$ $\rightarrow$ $^7$F$_1$ emission transition was studied under resonant excitation at different wavelengths within the $^7$F$_0$ $\rightarrow$ $^5$D$_0$ band. In order to explore the local structure of the systems, crystal-field analysis was applied assuming C$_{2v}$ site symmetry. Moreover, from the emission spectra of glass and glass-ceramic systems, Judd-Ofelt parameters $\Omega_t$ (t = 2, 4) were considered. Transition probability (A), stimulated emission cross-section ($\sigma$), radiative lifetime ($\tau_R$) and branching ratios ($\beta$) due to the transition $^5$D$_0$ $\rightarrow$ $^7$F$_J$ (J = 1, 2, 3 and 4) of Eu$^{3+}$ ions were evaluated in different local fields and their relative variations were discussed. The crystallization process, which converted the glass into glass-ceramic, promoted an important enhancement in the quantum efficiency, which was improved from 45 to 60\%.
The Nd3+ doped fluorochlorozirconate (FCZ) glass was prepared by melt-quenching method. The 3.9 μm emission from Nd3+ ions is attributed to the two-photon absorption process. The strong emission transition at 3.9 μm fluorescence peak intensity, corresponding to the 4G11/2→2K13/2 transition, is directly proportional to the NaCl concentration. With the increase of the Cl- ions amount, the mid-infrared (MIR) luminescent intensity is significantly enhanced. Additionally, the Judd-Ofelt (J-O) parameter Ω2 is larger than that of the fluorozirconate (FZ) glass, which indicates the covalency of the bond between RE ions and ligand is stronger as Cl- ions substitution of F- ions in chloride FZ glass. The X-ray diffraction (XRD) patterns show that the amorphous glassy state keeps the FZ glass network structure. In brief, the advantageous spectroscopic characteristics make the Nd3+-doped FCZ glass be a promising candidate for application of 3.9 μm emission.
This paper evaluates the spectroscopic properties of the Erbium (Er³⁺) ions doped magnesium zinc sulfophosphate glass system synthesized via melt-quenching method. Prepared glass samples are characterized using UV–Vis–NIR absorption and photoluminescence (PL) spectroscopy to determine the Er³⁺ ions concentration dependent spectral characteristics. The absorption spectra displayed nine prominent absorption bands aroused from the ground state (⁴I15/2) to the excited state (⁴I13/2, ⁴I11/2, ⁴I9/2, ⁴F9/2, ²H11/2, ⁴F7/2, ⁴F3/2, ²H9/2 and ⁴G11/2) transitions of Er³⁺ ion. The intensity parameters ( ) and radiative properties associated to the spectral transitions of Er³⁺ ion are calculated using Judd-Ofelt (JO) expressions. Room temperature PL spectra revealed two significant emission bands centered at 541 and 654 nm. Appearance of luminescence intensity quenching beyond 1 mol% of Er³⁺ is attributed to the cross-relaxation mechanism. The value of stimulated emission cross-section for ⁴S3/2⁴I15/2 spectroscopic transition in Er³⁺ ion is found to be very high (85.8211 10⁻²² cm²). Present glass composition is demonstrated to be advantageous for various photonic applications.
The luminescence of Li2O–B2O3–P2O5–CaF2 glass doped with Tb3 +/Eu3 + under electron beam excitation have been investigated in detail. The excitation spectra, photoluminescence (PL), pulse cathodoluminescence (PCL) and luminescence decay kinetics were analyzed. The energy transfer efficiency from Tb3 + to Eu3 + ions was found to increase at increased concentration of Eu3 + ions. As the concentration of europium grew, the luminescence quenching was observed. The energy transfer from Tb3 + to Eu3 + was observed to occur through level ⁵D4 of terbium ions. It is shown that the luminescence decay kinetics of terbium ions at 485, 544, 622 and 700 nm depends on europium concentration.
We provide a protocol to measure out-of-time-order correlation functions. These correlation functions are of theoretical interest for diagnosing the scrambling of quantum information in black holes and strongly interacting quantum systems generally. Measuring them requires an echo-type sequence in which the sign of a many-body Hamiltonian is reversed. We detail an implementation employing cold atoms and cavity quantum electrodynamics to realize the chaotic kicked top model, and we analyze effects of dissipation to verify its feasibility with current technology. Finally, we propose in broad strokes a number of other experimental platforms where similar out-of-time-order correlation functions can be measured.
In this paper, a compact passively Q-switched praseodymium (Pr³⁺)-doped fiber laser at the wavelength of 635 nm with black phosphorus (BP) saturable absorber (SA) was first investigated. BP nanoflakes were manufactured by the liquid-phase-exfoliation method and then embedded into polyvinyl-alcohol (PVA) film for the experimental usage and a fiber pigtail mirror (FPM, by coating dielectric film onto the fiber-end face) was applied to realize a compact Pr³⁺-doped red fiber laser. By transferring a block of the BP-PVA thin film onto the FPM and then incorporating into the compact Pr³⁺-doped fiber laser, the Q-switched operation at 635 nm was achieved. The pulse-repetition rate of the visible-wavelength Q-switched fiber laser can be widely tuned from 108.8 to 409.8 kHz and the shortest pulse duration of this laser is 383 ns. These results reveal that the BP is an available SA for red-light lasers.
Titanium materials are ideal targets for selective laser melting (SLM), because they are expensive and difficult to machinery using traditional technologies. After briefly introducing the SLM process and processing factors involved, this paper reviews the recent progresses in SLM of titanium alloys and their composites for biomedical applications, especially developing new titanium powder for SLM. Although the current feedstock titanium powder for SLM is limited to CP-Ti, Ti–6Al–4V, and Ti–6Al–7Nb, this review extends attractive progresses in the SLM of all types of titanium, composites, and porous structures including Ti–24Nb–4Zr–8Sn and Ti–TiB/TiC composites with focus on the manufacture by SLM and resulting unique microstructure and properties (mechanical, wear/corrosion resistance properties).
Graphene is an attractive photoconductive material for optical detection due to its broad absorption spectrum and ultra-short response time. However, it remains a great challenge to achieve high responsivity in graphene detectors because of graphene's weak optical absorption (only 2.3% in the monolayer graphene sheet) and short photo-carrier lifetime (< 1 ps). Here we show that metallic antenna structures can be designed to simultaneously improve both light absorption and photo-carrier collection in graphene detectors. The coupled antennas concentrate free space light into the nano-scale deep-subwavelength antenna gaps, where the graphene light interaction is greatly enhanced as a result of the ultra-high electric field intensity inside the gap. Meanwhile, the metallic antennas are designed to serve as electrodes that collect the generated photo-carriers very efficiently. We also elucidate the mechanism of photoconductive gain in the graphene detectors and demonstrate mid-infrared (mid-IR) antenna-assisted graphene detectors at room temperature with more than 200 times enhancement of responsivity (~0.4 V/W at λ_0=4.45 μm) compared to devices without antennas (<2 mV/W).
Density changes between sheared zones and their surrounding amorphous matrix as a result of plastic deformation in a cold-rolled metallic glass (melt-spun Al88Y7Fe5) were determined using high-angle annular dark-field (HAADF) detector intensities supplemented by electron-energy loss spectroscopy (EELS), energy-dispersive X-ray (EDX) and nano-beam diffraction analyses. Sheared zones or shear bands were observed as regions of bright or dark contrast arising from a higher or lower density relative to the matrix, respectively. Moreover, abrupt contrast changes from bright to dark and vice versa were found within individual shear bands. We associate the decrease in density mainly with an enhanced free volume in the shear bands and the increase in density with concomitant changes of the mass. This interpretation is further supported by changes in the zero loss and Plasmon signal originating from such sites. The limits of this new approach are discussed.
High power lasers are a tool that can be used to determine important parameters in the context of Warm Dense Matter, i.e. at the convergence of low-temperature plasma physics and finite-temperature condensed matter physics. Recent results concerning planet inner core materials such as water and iron are presented. We determined the equation of state, temperature and index of refraction of water for pressures up to 7 Mbar. The release state of iron in a LiF window allowed us to investigate the melting temperature near the inner core boundary conditions. Finally, the first application of proton radiography to the study of shocked material is also discussed.
Spectroscopic properties of Nd3+ in barium fluorophosphate glassy matrix containing sulphate have been analysed by fitting the experimental data with the standard Judd–Ofelt theory. Various spectroscopic parameters viz. radiative transition probabilities, radiative decay time, fluorescence branching ratios, electric dipole line strengths, stimulated emission cross sections and optical gain of the principal fluorescence transition from the 4F3/2 metastable level are obtained. Results show that addition of sulphate to the fluorophosphate matrix will enhance the fluorescence spectral properties of Nd3+ considerably. Quantum efficiency of the 4F3/2 emission is found to be higher than that of fluorophosphate glasses and stimulated emission cross section of the 4F3/2→4I11/2 transition is the highest among all reported values. Quantitative estimation of the non-radiative processes such as multiphonon relaxation and quenching by water content was carried out and the results show that the water content is below the critical level for optimum laser performance.
We present a comprehensive review of work on the Er3+-doped tellurite glass microsphere laser. We discuss the optical properties of Er3+-doped tellurite glass, including the emission cross section, the absorption cross section, and the lifetime analysis. Whispering-gallery modes in microspheres and fiber-taper coupling schemes are described, and theoretical analysis is performed for optimization. Finally, lasing characteristics such as the threshold, the lasing wavelength, and the temperature dependence of the microsphere laser are analyzed. Microsphere lasers with different Er2O3 doping concentrations have been fabricated and examined. A state-of-the-art L-band microsphere laser with 124.5-µW maximum output power is demonstrated. These miniature microsphere lasers have great potential and have attracted considerable attention because of their versatility for signal processing, fiber communication, and photon computation, as well as laser stabilization and sensing applications.
A method for LiNi 0.8Co 0.2O 2 films fabrication by pulsed laser deposition (PLD), is presented. The effect of several variables such as growth temperature, oxygen partial pressure, and target composition on the growth mode, structure, and phase stability is investigated. The phase diagram of the microstructure development in this PLD films is proposed, which could provide a way to optimize the deposition process parameters to grow films with controlled structure for the desired technological applications. The applicability of this films in microbattery is demonstrated, and it is expected to contribute significantly to science and technology.
Cascading the <sup>4</sup>I<sub>11/2</sub>→<sup>4</sup>I<sub>13/2</sub> transition at 2.8 μm and <sup>4</sup>I<sub>13/2</sub>→<sup>4</sup>I<sub>15/2</sub> transition at 1.6 μm offers a solution to the thermal management of high power Er<sup>3+</sup>-doped fluoride fiber lasers. We demonstrate an output power of 8.2 W at 2.8 μm from an Er<sup>3+</sup>-doped fluorozirconate fiber laser with 56 W of launched pump power at 975 nm by cascade laser operation with the 1.6-μm ground-state transition. By careful selection of the Er<sup>3+</sup> concentration that prevents significant interaction between Er<sup>3+</sup> ions, it is shown that cascade lasing can occur from simple resonator arrangements including Fresnel reflection from the ends of the fiber only. The unsaturated output power suggests that no competing transitions are oscillating which advocates that radiative quenching of the metastable <sup>4</sup>I<sub>13/2</sub> level provides an elegant way of reducing undesired heat generation. We show that core temperature increases at the tip of the pumped end of the fiber can be an order of magnitude lower than fiber lasers employing single transition oscillation. The potential of further power scaling is demonstrated and the experimental results are verified with the use of a numerical model.