Doped ZBLAN Fiber Research Articles

Dual-wavelength single-frequency Tm:ZBLAN fiber amplifier operating at 1.94 and 2.33 μm

We report here, to the best of our knowledge, the first dual-wavelength single-frequency thulium-doped fiber amplifier operating at 1.94 and 2.33 μm. The single-stage, Tm3+-doped ZBLAN fiber amplifier, ground-state pumped by a 793-nm laser diode, yielded a stable output power of 1.45 W at 2332 nm and 7.4 W at 1939 nm. The injection of 1.94-μm seed effectively suppresses parasitic lasing in the 2.33-μm Tm fiber amplifier. The experiment investigated the competitive relationship between the 2-μm transition and the 2.3-μm transition, and the results suggest that the injection of 1.94-μm seeds is beneficial to the improvement of 2.33-μm efficiency, while the injection of 2.33-μm seed slightly reduces the 1.94-μm efficiency.

Switchable red, blue-green emission using polarized optical fibre loop mirror in upconversionPr3+/Yb3+-doped ZBLAN fibre laser system

This manuscript experimentally demonstrates a switchable upconversion visible fibre laser system. The laser system is based on a linear fibre laser cavity with Praseodymium–Ytterbium codoped fluorozirconate (ZBLAN) optical fibre as a gain medium. The fibre laser cavity integrates a fibre loop mirror with a polarization controller to switch between multiple visible spectra. The optical fibre laser source provides dual blue and green emission with a centred wavelength of 490 nm and 520 nm, as well as red emission with a bandwidth of 115 nm, from orange to deep red with peaks centred at 605 nm, 635 nm, 693 nm, and 715 nm. The mentioned emissions can be switched and combined to generate almost pure white emission, white emission with high deep-red contribution, and vivid red. In addition, it demonstrated visible emission separation in an upconversion laser system via polarization, generating a wideband switched red-blue-green light source.

Direct generation of a 635 nm red random laser based on praseodymium (Pr)-doped ZBLAN fiber.

Visible random fiber lasers have garnered significant attention due to their unique emission properties and potential applications in various fields. We first, to the best of our knowledge, demonstrateda compact all-fiber structure, red wavelength, and random fiber laser (RFL) based on a double-clad Pr-doped ZBLAN fiber. The simple half-open cavity consists of a high-reflectivity fiber pigtail mirror and the Pr-doped ZBLAN fiber. The Pr-doped ZBLAN fiber not only served as a gain medium but also offered random backward scattering. We investigated the effects of different lengths on output power and slope efficiency of the RFL. For 21 m Pr-doped fiber, the RFL emitted a maximum output power of 208.50 mW with a slope efficiency of 11.09%. For 15 m Pr-doped fiber, the maximum power decreased to 120.18 mW with the slope efficiency of 7.27%. We are also numerically simulating the output power versus the pump power at different fiber lengths based on power steady-state light propagation equations. This novel RFL has the potential for broad applications in fields such as display technology, spectroscopy, biomedical imaging, and optical sensing due to its unique properties and simple all-fiber structure.

Generation of 2.8 µm fiber laser using an Erbium‐doped ZBLAN double‐clad fiber in a linear‐cavity‐free space experimental setup

AbstractMid‐infrared (MIR) fiber lasers are highly demand after for a variety of technological applications, including uses such as laser surgery, frequency metrology, and spectroscopy. This paper demonstrates a stable continuous‐wave laser operation in the 2.8 µm using an Er3+‐doped ZBLAN fiber operating in a free space experimental setting. A laser output power of 12.4 mW was attained in a linear cavity when this fiber was pumped at 2.9 W of 980 nm laser diode.

An experimental and theoretical study on Dy3+-doped ZBLAN fiber laser, core-pumped at 1.1 μm

An experimental and theoretical investigation into a core-pumped Dy3+-doped ZBLAN fiber laser with 1.1 μm pumping was conducted to figure out a configuration for better slope efficiency. First, the laser was experimentally constructed with a simple Fabry–Pérot cavity incorporating AlF3 no-core fiber endcaps. The maximum output power of 607 mW was obtained readily with a slope efficiency of 25%. Next, a 5-energy level model was adopted for a numerical simulation to figure out the optimum output mirror reflectivity for the particular experimental laser setup in terms of slope efficiency. The best slope efficiency of 30% was shown to be obtainable with an output mirror of a 22% reflection.

Comparison of 970- and 790-nm pumping for a 2.8 μm, Er3+-doped ZBLAN fiber laser

Comparison of 970- and 790-nm pumping for a 2.8 μm, Er3+-doped ZBLAN fiber laser

Multi- and Dual-Wavelength Laser at S-Band by Incorporating All-Fiber Lyot Filter in Tm3+-Doped ZBLAN Fiber: A Millimeter-Wave Generation Toward 5-G Communication

Multi- and Dual-Wavelength Laser at S-Band by Incorporating All-Fiber Lyot Filter in Tm³⁺-Doped ZBLAN Fiber: A Millimeter-Wave Generation Toward 5-G Communication

Highly stable pulsed fiber laser generation modulated by chromium iodide film

Abstract Highly stable pulsed fiber lasers are key optical components in optical communication, optical sensing, and precision micromachining systems due to the high beam quality, high peak power, and compact configurations. However, the available optical modulators in the fiber laser suffer from the operation bandwidth limitations and poor long-term physicochemical stability. Here, we have investigated the broadband nonlinear optical absorption behavior of the chromium iodide (CrI3) film, which exhibits broadband saturable absorption towards the mid-infrared regime and excellent long-term stability. The conventional soliton fiber laser operating at telecom wavelength has been obtained from an Er3+-doped fiber laser (EDFL) utilizing CrI3 film with a signal-to-noise ratio (SNR) of 92.4 dB and a pulse width of 492 fs. In addition, a passively Q-switched operation around 2.8 μm has also been obtained from an Er3+-doped ZBLAN fiber laser (EDZFL) modulated by the CrI3 film with a SNR of 46.8 dB and a pulse width of 766 ns. The demonstration shows that the CrI3 film exhibits robust broadband optical modulation, and may make inroads for developing highly stable ultrafast optoelectronic devices.

Dual-wavelength pumped 2.8 μm Er-doped ZBLAN fiber laser with high overall optical efficiency

A dual-wavelength pumped erbium (Er3+) doped ZBLAN fiber laser operating at 2.8 μm is experimentally demonstrated. The laser is cladding-pumped at 976 nm and core-pumped at 1.7 μm. The 1.7 μm pump induces an energy recycling via the 4I13/2→4I9/2 excited state absorption (ESA), which enables the laser to operate under very low 976 nm pump power. Thanks to the core-pumping scheme of the 1.7 μm pump, the required fiber length to support efficient lasing is short. An impressive overall optical efficiency (33%, defined as the ratio of the output power to the sum of the 976 nm and the 1.7 μm pump power) is realized using the laser. Higher efficiency up to 40% is achievable by using more intense 1.7 μm pump.

Direct generation of 3.17 mJ green pulses in a cavity-dumped Ho3+-doped fiber laser at 543 nm

High-energy pulsed lasers in the green spectral region are of tremendous interest for applications in space laser ranging, underwater detection, precise processing, and scientific research. Semiconductor pulsed lasers currently are difficult to access to the so-called “green gap,” and high-energy green pulsed lasers still heavily rely on the nonlinear frequency conversion of near-IR lasers, precluding compact and low-cost green laser systems. Here, we address this challenge by demonstrating, for the first time to the best of our knowledge, millijoule-level green pulses generated directly from a fiber laser. The green pulsed fiber laser consists of a 450 nm pump laser diode, a Ho3+-doped ZBLAN fiber, and a cavity-dumping module based on a visible wavelength acousto-optic modulator. Stable pulse operation in the cavity-dumping regime at 543 nm is observed with a tunable repetition rate in a large range of 100 Hz–3 MHz and a pulse duration of 72–116 ns. The maximum pulse energy of 3.17 mJ at 100 Hz is successfully achieved, which is three orders of magnitude higher than those of the rare-earth-doped fiber green lasers previously reported. This work provides a model for compact, high-efficiency, and high-energy visible fiber pulsed lasers.

High-gain single-frequency Tm3+-doped ZBLAN fiber amplifier at 2.33 μm.

We report here, to the best of our knowledge, the first high-gain, single-frequency Tm3+-doped fiber amplifier operating at the 2.3-μm band with conventional ground-state pumping transition (3H6→3H4) at 793 nm. The gain fiber is an 8.5-m-long ZBLAN fiber with a Tm3+ doping concentration of 3 mol.%, and the seed is a single-frequency distributed feedback diode laser operated at 2331.9 nm. A gain up to 24.1 dB is generated for ∼14 W of launched pump power with the maximum output power of 246 mW. The competitive 3F4 →3H6 laser transition at ∼2 µm is also investigated, and the prospects for further power scaling are discussed.

Watt-Level High-Efficiency Deep-Red Ho3+:ZBLAN Fiber Laser

To date, Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fibers have been investigated as a viable route for deep-red fiber lasers. However, high output performance deep-red fiber lasers around 750 nm have been proven challenging to achieve due to limitations in both the excitation source and pumping mechanism. In this study, we use a home-made 640 nm pump source to develop a deep-red laser with a high pumping rate, and obtain a compact watt-level high efficiency deep-red laser output. Population inversion is achieved by strong excited state absorption in a Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped ZBLAN fiber. We realize a maximum 1.46 W deep-red fiber laser operating at 752.6 nm, and its slope efficiency is as high as 53%. The improved rate equations are used to describe the quasi-four-level system, and the experimental results agree well with the simulations. Moreover, with the development of blazed grating, we demonstrate a tunable deep-red fiber laser with a tuning range of 13.7 nm, from 746.5 to 760.2 nm, which is the widest tuning range of Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fiber laser at deep-red wavelengths.

Modeling of an Er3+-Doped ZBLAN Fiber Laser With Ion Clustering Effect

In this study, we proposed a numerical model incorporating ion clustering effect for an Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped ZBLAN fiber laser. Our proposed model does not use weak-interaction (WI) energy transfer parameters, instead, it is based on two separate rate equations for isolated and clustered ions, respectively, using conventional ionic interaction parameters, unlike the previously proposed WI model. We verified the efficacy of our proposed model by comparing the numerically calculated output curves with the experimentally measured ones in a Fabry-Pérot laser setup based on two different lengths of commercially available Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped ZBLAN fiber. The proposed model can readily provide an accurate prediction of the laser output performance without using WI energy transfer parameters. In addition, with the numerical calculation of the model, the relative number of clustered ions in a commercial ZBLAN fiber was indirectly found to be ∼18.1%. Lastly, we compared the calculation results of our model with those with strong-interaction (SI) and WI model, which are commonly used for Er <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped ZBLAN fiber lasers.

Numerical analysis and optimization of 2.8 μm lightly-erbium-doped fluoride fiber laser based on cascaded transition

Er&lt;sup&gt;3+&lt;/sup&gt;-doped ZBLAN fiber laser is a promising approach to producing 2.8 μm mid-infrared (MIR) laser. The long lifetime of the lower-laser-level &lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;13/2&lt;/sub&gt; often results in serious self-terminating effect which harms the laser power and efficiency significantly, especially for the active fiber with low dopant concentration which is preferred for weak thermal issues but cannot depopulate the lower-laser-level effectively via the up-conversion process. The 1.6 μm lasing (&lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;13/2 &lt;/sub&gt;→ &lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;15/2&lt;/sub&gt;) in Er-ZBLAN fiber could deplete the population on &lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;13/2&lt;/sub&gt;. Therefore, cascaded 2.8 μm and 1.6 μm lasing in Er&lt;sup&gt;3+&lt;/sup&gt;-doped ZBLAN fiber provides a promising solution to the self-termination effects on laser power scaling. Moreover, the &lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;13/2 &lt;/sub&gt;→ &lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;15/2&lt;/sub&gt; 1.6 μm laser also has some overlap with the &lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;13/2 &lt;/sub&gt;→ &lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;9/2&lt;/sub&gt; excited state absorption (ESA) spectrum. The ions on the &lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;9/2&lt;/sub&gt; level would then relax to the upper-laser-level of 2.8 μm lasing (&lt;sup&gt;4&lt;/sup&gt;I&lt;sub&gt;11/2&lt;/sub&gt;), and results in enhanced laser efficiency. In general, the 1.6 μm cascaded lasing in 2.8 μm Er-ZBLAN fiber laser involves both lasing and ESA. The two processes have different spectra and different influences on the 2.8 μm laser gain. Therefore, there should exist an optimal wavelength of the 1.6 μm laser, which would balance the two processes, ensuring the lower-laser-level depopulation while maximizing the ion recycling. Therefore, we develop a comprehensive numerical model of cascaded 2.8 μm and 1.6 μm lasers based on Er-ZBLAN fiber. After the numerical model is verified by the previous experimental results, the effects of MIR and 1.6 μm lasing wavelengths on the power and conversion efficiency of 2.8 μm laser are investigated in depth. The results show that a suitable trade-off between the two processes can be reached with the cascaded lasing wavelength of 1610 nm, for the optimized 2.8 μm laser power/efficiency. Moreover, the influence of 1.6 μm laser cavity feedback on the power/efficiency characteristics of the 2.8 μm laser is also investigated. It is found that the feedback at 1.6 μm is very low, even only 4% is provided by the Fresnel reflection of the fiber facet, which can effectively generate 1.6 μm laser and significantly improve the efficiency of 2.8 μm laser.

Yellow pumped Pr3+-doped ZBLAN fiber laser at 1015 nm.

To date, lasing in the visible to near-infrared wavelengths has been studied for praseodymium-doped fluoride fibers with the upper energy level of 3P0. In this Letter, a fiber laser operating at 1015 nm has been realized for the first time, to the best of our knowledge, which confirms a new mechanism where 1D2 can be the upper energy level. A maximum output power of 241 mW, with a slope efficiency of 30%, was achieved by using a 150-cm-long active fiber pumped at a maximum pump power of 823 mW. Furthermore, the broad emission spectra of Pr3+-doped fibers in the near-infrared band have been exploited as new, to the best of our knowledge, spectral sources.

Te Film as a Saturable Absorber for the Mid-Infrared Er3+-Doped ZBLAN Fiber Laser

We demonstrate a Q-switched Er3+-doped ZBLAN fiber laser at 2.8 µm mid-infrared (mid-IR) region achieved by adopting Te as the saturable absorber mirror (SAM). The modulation depth and saturation intensity of the Te-SAM were measured to be ∼7.2% and 10.81 MW∕cm2, respectively. Stable Q-switched laser pulses with the maximum pulse energy of 3.05 µJ and the minimum pulse width of 0.457 µs at the launched pump power of 4.51 W were obtained. Maximum average output power of 357 mW with repetition rate of 116.98 kHz were achieved. The signal-to-noise ratio (SNR) is 52 dB, which is higher than that of most 2.8 µm mid-infrared Q-switched fiber lasers reported so far. To the best of our knowledge, this is the first demonstration from a Q-switched fiber laser at 2.8 µm based on a Te-SAM.

High power downconversion deep-red emission from Ho3+-doped fiber lasers

Abstract It has been a big challenge in decades for Ho3+-doped fiber laser to produce high emission power in deep-red due to its intrinsic long carrier lifetime in 5I7 energy level. Here, we advance the development of this visible fiber lasers by a novel pumping method that leverages the advantages of blue laser diode downconversion mechanisms to fully pumping, while shortening the lifetime of the lower energy level of the deep-red laser through excited state absorption. For the first time, we demonstrate a downconversion fiber laser using a single wavelength of 532 nm solid-state laser pump source to excite the Ho3+-doped ZBLAN fiber, which achieves a record high maximum output power of 1.64 W at 752.10 nm, as well as free-running of deep-red lasers with watt-level output. This technology represents a milestone in high power deep-red fiber lasers. Importantly, it is readily to be extended to other wavelengths that evidenced its huge application potentials in fiber laser industry.

Spectral filtering effect on the ultrafast mid-infrared Er3+-doped ZBLAN fiber laser.

We investigate the spectral filtering effect on the mid-infrared ultrafast Er3+-doped ZBLAN fiber laser based on nonlinear polarization evolution (NPE). A broad wavelength tuning range from 2720 nm to 2800 nm is achieved using a diffraction grating as the narrowband filter. Furthermore, numerical simulations are also carried out so that, by inserting a highly nonlinear fiber combined with an appropriate spectral filter in the laser system, a 329 nm ultra-broadband spectrum with a Fourier transform limit pulse as short as 47 fs can be achieved. Our results are conducive to understanding the spectral filtering effect on the lasing performance of mid-infrared ultrafast fiber lasers.

Fundamental and Harmonic Self Mode-locking in Mid IR Heavily Doped Fiber Lasers

Abstract: Harmonic self mode-locking effects are observed in heavily doped fiber lasers operating near 3 μm. The temporal profiles for the output of an Er-ZBLAN fiber laser operating at ~2.7 μm and an Ho, Pr-ZBLAN fiber laser operating at ~2.87 μm are reported. Stable second harmonic mode-locking is observed in the Er-ZBLAN fiber laser under 970nm pumping for an Er concentration of 50000 ppm, while unstable harmonic mode-locking of order of between 1-1/7 times the round cavity round trip time was observed for the higher concentration of 80000 ppm and for all pump powers. Unstable harmonic mode-locking is observed in the Ho, Pr-ZBLAN fiber laser when pumped at 1064nm, for fiber lengths up to 13m and for all pump powers. The experimental mode-locked pulse train periods are found to be consistent with theoretical analysis. The origin and properties of harmonic self mode-locking in heavily doped ZBLAN fiber lasers operated near 3 μm are discussed. Keywords: Er-ZBLAN fiber laser, Ho, Pr-ZBLAN fiber laser, Self mode-locking, Harmonic self mode-locking. PACS: Fiber lasers, 42.55.Wd, Mode locking, 42.60.Fc.

High-power 813-nm Tm3+-doped ZBLAN fiber MOPA with signal-light photodarkening suppression.

The photodarkening suppression effect of an 813-nm Tm3+-doped ZBLAN fiber amplifier has been investigated. We have experimentally observed that a photodarkened fiber can be bleached by an 813-nm light and that the photoinduced loss during the amplifier operation is effectively suppressed with the help of the high-power signal. To the best of our knowledge, this is the first investigation of the photodarkening suppression by using a higher power signal in Tm3+-doped fiber amplifiers. Based on these signal photodarkening suppression effects, we have designed a multistage fiber amplifier, and demonstrated the stable operation of the 1.15-W fiber master oscillator power amplifier at 813 nm without additional photobleaching light.