ZrF4-BaF2-LaF3-AlF3-NaF Research Articles

Spectrally Flat Supercontinuum Generation in a ZBLAN Fiber Pumped by Erbium-Doped Mode-Locked Fiber Laser

We have experimentally demonstrated the flat supercontinuum (SC) generation using a 10-m-long ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fluoride fiber pumped by an erbium-doped mode-locked fiber laser incorporating carbon-nanotube-based saturable absorbers. In order to improve the spectral flatness of SC, the standardized single-mode fiber with different lengths is connected to the output of the mode-locked fiber laser before the pulse amplification. The generated SC with ZBLAN fiber exhibits the best spectral flatness with fluctuation less than 1.29dB over the wavelength of 1571.8nm–1803.1nm, showing potential applications in optical sensing.

A high-birefringent photonic quasi-crystal fiber with two elliptical air holes

A photonic quasi-crystal fiber (PQF) with high birefringence based on ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) is described. There are two elliptical air holes in the core to increase birefringence and the outer air hole array has a twelve-fold Stampfli-type quasi-crystal structure. ZBLAN reduces absorption loss in the infrared region resulting in higher birefringence. The birefringence and confinement loss of the PQF are analyzed numerically by the full-vector finite element method. Birefringence is higher than that of conventional polarization-maintaining fibers due to the two elliptical air holes in the center and reaches the maximum of 4.15×10−2 at a wavelength of 2 μm. The novel structure has great potential in high-performance optical devices.

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.

Phase‐Separation Engineering of Glass for Drastic Enhancement of Upconversion Luminescence

AbstractOptical gain materials are of fundamental importance for various applications, such as lasers, lighting, optical communication, microscopy, and spectroscopy. However, the requirements for high luminescence efficiency and excellent thermodynamic stability of materials are always contradictory. As a result, wide applications of optical materials in high‐temperature, high‐humidity, and high‐power laser‐irradiated environments are restricted. Here, a facile approach based on phase‐separation engineering is proposed to modulate the thermodynamic stability and enhance the luminescence efficiency of optical gain materials. It is shown that the thermodynamic stability and luminescence efficiency of the phase‐separated fluorosilicate (FS) gain glass are both enhanced dramatically when the SiO2 concentration is optimized. Owing to the confinement effect of phase‐separation network structure on active ions, the upconversion (UC) luminescence efficiency of the designed glass is 150 times higher than that of traditional FS glasses and even seven times higher than that of ZBLAN (ZrF4‐BaF2‐LaF3‐AlF3‐NaF) glass, which is the most commonly used material for UC fiber lasing applications. These intriguing properties of the glass indicate that phase‐separation engineering not only provides a powerful solution to conquer the conventional contradiction between thermodynamic stability and luminescence efficiency but also offers significant opportunities for manufacturing a wide range of optical composites with multiple functions.

Watt-level, all-fiber, spectrally flat, and ZBLAN fiber-based MIR supercontinuum extending to 4.6 μm with a record power ratio beyond 3.8 μm

An all-fiber midinfrared supercontinuum with 20-dB spectral coverage from 1.9 to 4.6 μm is demonstrated with a record power ratio beyond 3.8 μm. The supercontinuum is generated in a piece of single-mode ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fiber pumped by a broadband, single-mode thulium-doped fiber amplifier. Under the optimized pulse repetition rate and ZBLAN fiber length, the output spectrum has a good flatness. The power ratio beyond 3.8 μm is measured to be over 30% when the average output power reaches 1.11 W. Based on the all-fiber configuration, we have provided a compact, reliable, and promising supercontinuum source for further spectral extension into the midinfrared region where a high long-wavelength ratio is preferred.

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.

Mid-IR supercontinuum generation in a single-mode ZBLAN fiber by erbium-doped fiber laser

We present a compact broadband supercontinuum (SC) generation in a single-mode fluorozirconate ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber pumped by femtosecond pulses from an erbium-doped fiber laser (EDFL). The femtosecond seed pulses are generated through passive mode locking using carbon-nanotubes-based saturable absorber in EDFL ring cavity. An SC spectrum spanning from 1100 to 3200 nm with a spectral flatness of <8 dB has been obtained successfully from a single-mode ZBLAN fiber. A piecewise linear relationship of SC spectrum bandwidth with input pulse power is observed.

Towards a Supercontinuum Generation in an All-Fiberized Holmium-Doped ZBLAN Fiber Amplifier

A supercontinuum (SC) was first generated in a holmium-doped ZBLAN (ZrF4−BaF2−LaF 3−AlF3−NaF) fiber amplifier (HDZFA) with a spectral coverage of 2.03–2.9 μm, then was further red-shifted to 3.7 μm by cascading a piece of passive ZBLAN fiber. The amplifier consisted of a 2050-nm pulsed fiber laser and a piece of holmium-doped ZBLAN fiber (HDZF), which was in-band pumped by a 1950-nm continuous wave thulium-doped fiber laser. A fusion splicing was achieved between passive silica fiber and the HDZF. The spectral and power characteristics of the amplifier were carefully investigated. The SC obtained in the amplifier showed a spectrum ranging from 2.03 to 2.9 μm with an output power of 248 mW and a maximal slope efficiency of 43.3%. The spectral broadening in the amplifier was halted by a strong absorption induced by an excited state absorption (ESA) of Ho3+ in the range ∼2.7–2.8 μm. An SC with 20-dB spectral coverage of 2.05–3.71 μm was finally obtained by cascading a piece of passive single-mode ZBLAN fiber after the amplifier, with the purpose of overcoming the ESA-induced loss of holmium ions. To the best of our knowledge, this research is the first demonstration of an SC generation in an HDZFA.

Watt-level mid-infrared supercontinuum generation from 27 to 425 μm in an erbium-doped ZBLAN fiber with high slope efficiency

A watt-level mid-infrared supercontinuum (MIR-SC) spanning 2.7 to 4.25μm is generated in an erbium-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber amplifier (EDZFA). A broadband fiber-based SC covering 2.2-3.1μm region is used to seed the amplifier. The generated SC has a maximum output power of 1.75W with an overall slope efficiency of 20.5%. A normalized root mean square (RMS) in power of 0.5% shows that our system is highly stable. This research, to the best of the authors' knowledge, demonstrates both the record power and the record slope efficiency of in-amplifier MIR-SC generation to date.

Graphene/MoS2 heterostructure: a robust mid-infrared optical modulator for Er3+-doped ZBLAN fiber laser

We have prepared the graphene/MoS 2 heterostructure by a hydrothermal method, and presented its nonlinear absorption parameters and application as a nonlinear optical modulator in the mid-infrared region. Using the nonlinear optical modulator, stable passively Q-switched operation of an Er 3+-doped ZrF 4-BaF 2-LaF 3-AlF 3-NaF (ZBLAN) fiber laser at ∼2.8 μ m can be obtained. The Q-switched Er 3+-doped ZBLAN fiber laser can yield per-pulse energy up to 2.2 μJ with the corresponding pulse width and pulse repetition rate of 1.9 μs and 45 kHz, respectively. Our results indicate that the graphene/MoS 2 heterostructure can be a robust optical modulator for pulsed lasers in the mid-infrared spectral range.

Compact Two-Color Pr3+-Doped ZBLAN Fiber Lasers

ABSTRACTTwo-color laser simultaneous oscillation in compact trivalent praseodymium ion (Pr3+)-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber lasers is investigated. Fiber pigtails by coating high-reflective visible dielectric films are utilized as fiber mirrors (FMs) to construct compact all-fiber laser cavity. Reflectance/transmittance of FMs is intentionally designed to balance net gains and reduce gain competition of different lasable wavelengths in the constructed fiber lasers. By using two selected FMs with high reflectivity at green-light and low reflectivity at red-light, simultaneous green and red laser emission in all-fiber Pr3+-doped ZBLAN fiber laser is obtained. Moreover, simultaneous orange and red laser emission is also achieved with another selected FM of high reflectivity at orange-light and low reflectivity at red-light. Our work will provide an effective and easy method to construct compact special fiber (e.g.,ZBLAN fiber, chalcogenide fiber) lasers.

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.

Pulsed fluoride fiber lasers at 3 μm [Invited

Enormous performance gains have been made in fluoride-based fiber lasers operating around 3 μm due to advances in fiber fabrication and improvements in high-power pump diode technologies during the last decade. Pulsed fluoride fiber lasers capable of producing high-energy/high-peak power mid-infrared pulses are of significant interest for a variety of applications. Q-switched and mode-locked fiber lasers have been demonstrated with various techniques in recent years. In this paper, pulsed Er3+- and Ho3+-doped ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fiber lasers are reviewed, and our achievement of pulsed fiber laser sources at 3 μm is presented. Power/energy scaling of pulsed ZBLAN fiber lasers and their potential applications are discussed.

26 mJ Total Output from a Gain-Switched Single-Mode Er3+-Doped Zblan Fiber Laser Operating at 2.8 μ $$ \mu $$ m

We demonstrate a laser-diode-pumped gain-switched Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser operating in a single transverse mode at 2.8 \( \mu \)m. The laser pulses produced offer high-pulse energies, with repetition rates ranging from 50 Hz to 10 kHz and a slope efficiency of approximately 14.3% with respect to the launched pump power. The average power at the 50 Hz repetition rate is 1.33 W, giving a maximum total output pulse energy of 26.6 mJ per pump pulse. The fiber laser operates in a single mode, with beam quality factor M2 less than 1.2.

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.

Compact watt-level passively Q-switched ZrF4-BaF2-LaF3-AIF3-NaF fiber laser at 2.8 μ m using Fe2+:ZnSe saturable absorber mirror

A midinfrared (mid-IR) saturable absorber mirror (SAM) was fabricated by coating aluminum film on Fe2+:ZnSe crystal, based on the vacuum evaporation method. By employing the prepared SAM, we demonstrated a high-power passively Q-switched Er3+-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser at 2.8 μm. The highest output power in excess of 1.01 W was obtained with a pulse energy of 11.37 μJ and pulse duration of 0.73 μs, corresponding to a repetition rate of 88.84 kHz. To the best of our knowledge, these values represent the highest output power/pulse energy from a passively Q-switched ZBLAN fiber laser around 2.8 μm. Our results demonstrate that Fe2+:ZnSe SAM is a promising device for high-power/high-energy pulse generation in compact mid-IR fiber lasers.

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.

High-peak-power single-oscillator actively Q-switched mode-locked Tm3+-doped fiber laser and its application for high-average output power mid-IR supercontinuum generation in a ZBLAN fiber.

A single-oscillator actively Q-switched mode-locked (QML) thulium-doped silica fiber laser is presented and used to pump a ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber for mid-infrared (mid-IR) supercontinuum (SC) generation. The fiber laser provided high-peak-power levels directly from the oscillator delivering single mode-locked pulse energies up to 48 μJ, being 2-4 orders of magnitude higher than conventional continuous wave mode-locked lasers. By pumping a ZBLAN fiber specially designed for high-output-power SC generation, 7.8 W have been achieved in all spectral bands with a spectrum extending to 4.2 μm.

Compact self-Q-switched green upconversion Er:ZBLAN all-fiber laser operating at 543.4 nm.

We report the demonstration of a compact self-Q-switched green upconversion Er3+:ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber laser operating at 543.4 nm. The all-fiber green laser simply consists of a 45 cm high-concentration Er3+:ZBLAN fiber, a 976 nm pump source, and a pair of fiber end-facet mirrors. Under the strong excitation of the 976 nm pump laser, green upconversion lasing at 543.4 nm is achieved from the compact Er3+:ZBLAN fiber laser. Interestingly, the green laser exhibits stable self-Q-switching operation. As the 976 nm pump power is increased, the pulse repetition rate linearly increases from 25.9 to 50.8 kHz and the pulse width narrows from 7.2 to 1.95 μs. The Q-switched green laser has a pump threshold of 118 mW and a maximum output power of 6.9 mW with a slope efficiency of 30%. This is, to the best of our knowledge, the shortest-wavelength operation of a self-started or passively Q-switched fiber laser.