BaF2 LaF3 Research Articles

Modified fluorozirconate glasses doped with 4f- and 3d-cations

Fluoride glasses remain to be an attractive material for thirty years for optical applications lying in the visible and mid IR spectral range due to their low phonon energy (∼500-600 cm−1) and as a unique matrix for introducing rare earth activators. Modern materials science studies in the area of fluoride glasses are aimed at searching for the new modified compositions of these glasses with high optical homogeneity with the purpose of creating efficient active optical media in a wide spectral range. By modifying the composition of the glasses one can control the thermal, optical and spectroscopic properties for various applications. The information on glass-formation in the fluorozirconate system ZBLAN (ZrF4–BaF2–LaF3–AlF3–NaF) modified with “heavier” cations and anions, their physico-chemical and optical properties and areas of applications is presented in this review. Promising directions of practical application of such materials, doped with 4f- and 3d-cations in optoelectronics are discussed.

Optical Properties of Fluorozirconate Glasses Doped with Chromium Ions

Chromium trifluoride-doped fluoride glasses in the ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) system with partial substitution of fluorine for chlorine have been synthesized. The spectral data obtained confirm that chromium ions enter the glass structure and exhibit broadband luminescence caused by the 4T2 → 4A2 transition in the Cr3+ ion. The observed long-wavelength shift of the broadband luminescence band and Cr3+absorption bands in fluoride–chloride glass compared to fluoride glass corresponds to the expected behavior of the Cr3+ luminescence and absorption spectra when fluoride ions are replaced by chloride ions, which should lead to a weakening of the strength of the crystal field acting on Cr3+ ions. At room temperature, the luminescence of Cr3+ ions at 888 and 908 nm is strongly quenched due to the thermally stimulated nonradiative transition from the 4T2 excited state to the 4A2 ground state.

Influence of xenon difluoride on the optical properties of fluorozirconate and fluorohafnate glasses

To study the effect of xenon difluoride as a fluorinating agent on optical properties of glasses in ZBLAN (ZrF4–BaF2–LaF3–AlF3–NaF) and HBLAN (HfF4–BaF2–LaF3–AlF3–NaF) systems, their optical transmission in the range from UV to IR was investigated. The treatment of the initial fluorides with XeF2 was shown to lead to a broadening of the transmission region of the obtained glasses both in the UV and IR ranges. Moreover, the treatment of the batch with xenon difluoride leads to the removal of oxygen-containing impurities that absorb in the region of 2.8 μm.

Exploring interfacial reactions and optical properties of ZBLAN-based phosphor-in-glass color converters via spark plasma sintering for laser-driven lighting

Phosphor-in-glass (PiG) is extensively utilized as a color converter in laser-driven lighting. Despite its popularity, a noteworthy concern is the potential for interfacial reactions to occur between the phosphors and the glass matrix during high-temperature processing, leading to subsequent corrosion. Previous research suggests that spark plasma sintering (SPS) may effectively limit these reactions in silica glass-based PiGs. However, the reactivity of silica glass, lacking glass modifiers, towards phosphors is diminished, raising uncertainty about whether SPS can truly fabricate a PiG with improved interfacial morphology. Nonetheless, research pertaining to PiG fabrication using SPS with multi-component glass compositions remains scarce. In this study, an attempt is made to address this gap by employing a multi-component glass matrix - ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN), which is known for its high reactivity with phosphors, in the creation of PiGs through SPS. Lu3Al5O12:Ce3+ (LuAG) was embedded within ZBLAN glass, fabricated using SPS in merely 5 min at a temperature of 255 °C. The subsequent analysis focused on the interfacial microstructure and the optical properties of the thus prepared PiG samples. The results demonstrate that the lower-temperature and time-efficient sintering process of SPS successfully mitigate the interfacial reactions between the phosphor and the glass matrix. Consequently, a commendable luminous flux of 597 lm and luminous efficacy of 242 lm/W is achieved.

Recent advances in luminescence and lasing research in ZBYA glass

In the last few decades, fluoride glasses have attracted a growing interest due to their unique advantages compared to multi-component oxide glasses. Among them, the most studied and widely used were fluorozirconate glasses, represented by ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) glasses. However, compared with ZBLAN glasses, a kind of fluorozirconate glass with the components ZrF4–BaF2–YF3–AlF3 (ZBYA) has higher thermal and chemical stability. In this paper, we first introduce the advantages of ZBYA glasses compared to ZBLAN glasses. Then we review and discuss recent advances in research on luminescence and lasing in ZBYA glass and fiber. These studies suggest that ZBYA glass has strong potential for use as a gain medium material in high power mid-infrared fiber lasers.

Crystallization Behavior and Spectroscopic Properties of Erbium-Doped Chlorine-Substituted Fluorozirconate Glasses

We have prepared ErF3-doped glasses in the ZrF4–BaF2–LaF3–AlF3–NaF system containing chlorine ions substituted for fluorine ions. The crystallization behavior of the chlorine-substituted glasses has been studied at various BaCl2 and ErF3 concentrations. We have identified phases precipitating during heat treatment of the glasses and assessed the effect of chlorine substitution for fluoride on the optical absorption and IR luminescence in the glasses. The results demonstrate that chlorine substitution for fluorine causes the UV absorption edge of the glass to shift to longer wavelengths and produces an additional absorption in the visible spectral region. The formation of crystalline phases during heat treatment of the glasses leads to significant changes in the shape of the Er3+ luminescence bands at 0.98 and 1.55 μm.

Characterization of Yb-doped ZBLAN fiber as a platform for radiation-balanced lasers

Recent advances in power scaling of fiber lasers are hindered by the thermal issues, which deteriorate the beam quality. Anti-Stokes fluorescence cooling has been suggested as a viable method to balance the heat generated by the quantum defect and background absorption. Such radiation-balanced configurations rely on the availability of cooling-grade rare-earth-doped gain materials. Herein, we perform a series of tests on an ytterbium-doped ZrF 4 – BaF 2 – LaF 3 – AlF 3 – NaF (ZBLAN) optical fiber to extract its laser-cooling-related parameters and show that it is a viable laser-cooling medium for radiation balancing. In particular, a detailed laser-induced modulation spectrum test is performed to highlight the transition of this fiber to the cooling regime as a function of the pump laser wavelength. Numerical simulations support the feasibility of a radiation-balanced laser, but they highlight that practical radiation-balanced designs are more demanding on the fiber material properties, especially on the background absorption, than solid-state laser-cooling experiments.

Spectral analysis of short-wavelength emission by up-conversion in a Tm3+:ZBLAN dual-diode-pumped optical fiber

The fluorescence evolution along Tm3+-doped ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) optical fibers, as well as amplified spontaneous emission in the UV-IR region with emphasis on 350 nm, 365 nm, and 450 nm, is studied, estimating optimal fiber lengths for amplification within the region. The fibers were diode-pumped with single and double lines (687 and/or 645 nm). Double-line pumping presents a quite superior efficiency for producing UV-blue signals with the benefit of requiring very short fibers, around 20 cm, compared to single-line pumping requiring more than 50 cm. A virtual cycle in which the pumps enhance each other’s absorption is the key to these systems.

Synthesis of Glass-Ceramics in Mixed Fluorozirconate–Phosphate Systems

Fluorozirconate-phosphate glasses of the ZrF4–BaF2–NaPO3(LiPO3) and ZrF4–BaF2–LaF3–AlF3–LiPO3 systems doped with EuF3, ErF3, and NdF3 were studied by the differential-thermal (DTA) and X-ray diffraction (XRD) analysis, luminescence spectroscopy, scanning and transmission electron microscopy (SEM and TEM) methods. Addition of the phosphate component up to 20 mol % decreases the glass transition temperature and increases the glass stability to crystallization. Heat treatment in the range >Tg–Tc1 of glass transition and first maxima of crystallization temperatures causes crystallization of nanosized β-BaZrF6 particles. At LiPO3 (NaPO3) concentrations of more than 80 mol %, glasses containing a crystalline phase are formed during the synthesis process.

Optical Properties and Electron Paramagnetic Resonance Spectra of Zirconium Fluoride- and Hafnium Fluoride-Based Glasses Activated with MnO2 and EuF2

We have studied luminescence and electron paramagnetic resonance (EPR) spectra of manganese- and europium-activated fluorozirconate glasses in the ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) system and fluorohafnate glasses in the HfF4–BaF2–LaF3–AlF3–NaF (HBLAN) system in order to assess the oxidation state and spatial distribution of the activator ions. The manganese luminescence band has been shown to shift from the green (545 nm) to the red (610 nm) spectral region, and additional lines in the EPR spectrum of manganese have been observed to emerge in the EPR spectrum of manganese as a result of BaCl2 substitution for BaF2 in the ZBLAN glass. The ratio of the concentration of free activator ions to that of clustered ions has been estimated quantitatively. It has been shown that, at high doping levels, the manganese and europium ions in the glasses are predominantly clustered, and only a small part of them are present as isolated ions.

The 2- to 6- mid-infrared supercontinuum generation in cascaded ZBLAN and As2Se3 step-index fibers**Project supported by the National Natural Science Foundation of China (Grant Nos. 61435009, 61235008, and 61405254), the Fund from China Scholarship Council (Grant No. 201803170210), and Hunan Provincial Innovation Foundation for Postgraduate (Grant No. CX2018B008).

Fiber-based mid-infrared (MIR) supercontinuum (SC) sources benefit from their spectral brightness and spatial coherence that are needed for many applications, such as spectroscopy and metrology. In this paper, an SC spanning from to is demonstrated in cascaded ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) and As2Se3 step-index fibers. The pump source is a ZBLAN fiber-based MIR SC laser with abundant high-peak-power soliton pulses between 3000 nm and 4200 nm. By concatenating the ZBLAN fiber and the As2Se3 fiber, efficient cascading red-shifts are obtained in the normal dispersion region of the As2Se3 fiber. The spectral behavior of cascaded SC generation shows that the long-wavelength proportion of MIR SC generated in the ZBLAN fiber plays a critical role for further spectral extension in the As2Se3 fiber.

Crystallization Behavior of Glasses in the ZrF4–BaF2–LaF3–AlF3–NaF and HfF4–BaF2–LaF3–AlF3–NaF Systems Modified with Chlorine and Bromine Ions

We have prepared glasses in the ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) and HfF4–BaF2–LaF3–AlF3–NaF (HBLAN) systems in which fluorine anions are partially replaced by chlorine and bromine anions. Structural changes in the chlorine-substituted glasses have been investigated by Raman spectroscopy and their crystallization behavior has been studied by differential thermal analysis and X-ray diffraction. The results demonstrate a characteristic decrease in glass transition temperature (Tg) and the precipitation of fine-particle crystalline chloride and bromide phases in a temperature range well below the crystallization temperature (Tx) of the fluoride analogues. We have identified phases that crystallize during heat treatment of the glasses at various temperatures.

Optical Properties and Electron Paramagnetic Resonance of MnO2-Doped Fluorozirconate Glasses

We have studied luminescence and electron paramagnetic resonance (EPR) spectra of manganese-activated fluorozirconate glasses. In ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) glasses, manganese gives a green luminescence band peaking at 545 nm. Partial chlorine substitution for fluorine in the glass leads to a shift and broadening of the luminescence band. Complete BaCl2 substitution for BaF2 in ZBLAN〈Cl〉 fluoride chloride glass increases the peak emission wavelength to 610 nm. The observed distinctions between the EPR spectra of the Mn-doped ZBLAN and ZBLAN〈Cl〉 glasses correlate with those between their luminescence spectra. The effect of chlorine substitution for fluorine on the luminescence and EPR spectra of the fluorozirconate glass is tentatively attributed to a change in the oxidation state of the manganese ions.

Growth of Fluorite Solid Solution Crystals in the Ternary SrF2–BaF2–LaF3 System and Investigation of Their Properties

A series of three-component isostructural fluorite crystals (Sr1–xBax)0.7La0.3F2.3 (sp. gr. $$Fm{\bar {3}}m$$ , 0 ≤ x ≤ 1), the compositions of which belong to the Sr0.7La0.3F2.3–Ba0.7La0.3F2.3 polythermal section in the SrF2–BaF2–LaF3 system, has been grown for the first time by vertical directional crystallization. Optical, mechanical, and electrical properties of three-component (Sr1–xBax)0.7La0.3F2.3 and two-component M0.7La0.3F2.3 (M = Sr or Ba) crystals have been investigated and subjected to comparative analysis. It is shown that all three-component crystals (Sr1–xBax)0.7La0.3F2.3 are promising optical design materials.

Broadband near-infrared emission and energy transfer in Nd-Bi co-doped transparent silicate glass-ceramics for optical amplifiers

The Bi+-doped, Nd3+-doped, and Nd3+-Bi+ co-doped in SiO2–Al2O3–BaF2–LaF3–TiO2 transparent silicate glass-ceramics were fabricated by conventional melting-quenching technique. The super broadband near-infrared luminescence, decay time spectra in Nd3+-Bi+ co-doped transparent silicate glass-ceramics under 808 nm excitation were investigated. The interesting in this paper is due to energy transfer between Bi+ and Nd3+ ions already exists lead to super broadband NIR emission extending from 1050 to 1550 nm with a full-width at half-maximum (FWHM) of 480 nm which covered the whole O, E and S bands were observed in the Nd3+-Bi+ co-doped transparent silicate glass ceramics. In addition, based on the decay time spectra, mechanism of energy transfer processes between Bi+ and Nd3+ ions were also discussed and proposed.

Optical properties and X-ray luminescence of fluorohafnate glass doping with EuF2

The luminescence and optical absorption of Eu2+-doped fluorohafnate glasses in the HfF4–BaF2–LaF3–AlF3–NaF (HBLAN) system have been reported. It is shown that divalent europium does not luminesce in the fluorohafnate glass due to ionization of excited Eu2+. The Eu2+ luminescence appears after heat treatment of the HBLAN glass containing BaCl2. At X-ray excitation of the HBLAN glass the luminescence spectrum has a wide intrinsic band in the region of 250–450nm. The substitution of fluorine with chlorine results as a shift both of the intrinsic luminescence band and of the UV absorption edge to the region of the longer wavelengths.

The manipulated left-handedness in a rare-earth-ion-doped optical fiber by the incoherent pumping field

The left-handedness was demonstrated by the simulation with a three-level quantum system in an Er3+-dopped ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAFN) optical fiber. And the left-handedness can be regulated by the incoherent pumping field. Our scheme may provide a solid candidate other than the coherent atomic vapor for left-handedness, and may extend the application of the rare-earth-ion-doped optical fiber in metamaterials and of the incoherent pumping light field in quantum optics.

SESAM $Q$ -Switched Ho3+-Doped ZBLAN Fiber Laser at 1190 nm

We report a semiconductor saturable absorber mirror $Q$ -switched holmium (Ho3+)-doped ZrF4–BaF2–LaF3–AlF3–NaF fiber laser operating at ~1190 nm in a linear cavity. Stable $Q$ -switched operation was established at a threshold pump power of 92.8 mW with a repetition rate of 26.1 kHz and a pulsewidth of $4~\mu \text{s}$ . The repetition rate increased and the pulsewidth decreased with an increasing pump power. When the pump power was increased to 830 mW, 800-ns $Q$ -switched pulses with a pulse energy of $0.18~\mu \text{J}$ at a repetition rate of 170 kHz were generated.

Efficient chirped-pulse amplification based on thulium-doped ZBLAN fibers

We demonstrate a chirped-pulse amplifier system operating around 1900 nm using thulium-doped ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) fibers. The pulses from a thulium-doped ZBLAN fiber laser oscillator are stretched by a passive ZBLAN fiber and subsequently amplified in a double-clad thulium-doped ZBLAN fiber to an average power of 6.9 W at a pump power of 17 W. We found that ZBLAN fibers require a much lower pump and/or seed power than silica fibers for efficient amplification. The amplified pulses are compressed to a duration of 150 fs with an average power of 3.9 W.

Scaling all-fiber mid-infrared supercontinuum up to 10 W-level based on thermal-spliced silica fiber and ZBLAN fiber

We demonstrate an integrated all-fiber mid-infrared (mid-IR) supercontinuum (SC) source generated by a 1.95 μm master oscillator power amplifier system and a single-mode ZBLAN (ZrF4–BaF2–LaF3–AlF3–NaF) fiber. The maximum average output power is 10.67 W with spectral bandwidth covering from ∼1.9 to 4.1 μm. The single-mode ZBLAN fiber and silica fiber are thermal-spliced to enhance the robustness and practicability of the system. It is, to the best of our knowledge, the first high-power integrated compacted all-fiber mid-IR SC source based on thermal-spliced silica fiber and ZBLAN fiber.