Double-clad Fiber Laser Research Articles

10-Watt diode-pumped red Pr:ZBLAN double-clad fiber laser

10-Watt diode-pumped red Pr:ZBLAN double-clad fiber laser

Modeling of rare-earth-doped double-clad fiber laser based on rate equations with spatially averaged parameters

A mathematical model of a rare-earth doped double-clad fiber laser based on rate equations with spatially averaged parameters laser has been developed. Analytical expressions for the threshold absorbed pump power, slope efficiency and laser output power have been obtained for the CW regime. It has been shown that the results of output power calculations using the analytical model for CW double-clad ytterbium and neodymium doped lasers are in a good agreement with the results obtained using numerical models described in literature. A quantitative criterion for the applicability of the presented analytical model for calculating the parameters of double-clad fiber lasers has been proposed. The applicability of the proposed model to describe the transient stage of the operation of a fiber laser under continuous pumping has been demonstrated.

108 fs high-power mode locked double-clad ytterbium-doped fiber laser using FePS3 saturable absorber

108 fs high-power mode locked double-clad ytterbium-doped fiber laser using FePS3 saturable absorber

High-energy single-longitudinal-mode Q-switched double-cladding fiber laser based on the injection seeding technique.

This paper demonstrates a high-energy, single-longitudinal-mode (SLM), actively Q-switched fiber laser based on the injection seeding technique. The large-mode-area double-cladding fiber is used as the gain medium to improve energy storage. Simultaneously, by using the linear electro-optic effect of the negative uniaxial crystal (β-B a B 2 O 4, BBO), a matching frequency-shift-free Q-switch with high damage threshold and high extinction-ratio is designed. Before reaching the stimulated Brillouin scattering threshold, the SLM Q-switched pulses can be achieved with energy higher than 15µJ over a wide range of repetition rates from 10 to 80kHz, and the maximum output power reaches 1.2W at the repetition rate of 80kHz, which may be the highest output pulse energy for such a SLM Q-switched fiber laser so far, to our best knowledge.

The Double-Clad Fiber Laser

The Double-Clad Fiber Laser

Deep-red double-clad fiber laser at 717 nm.

We report on a double-clad fiber laser operating on the 3P0 → 3F4 Pr3+ transition (in the deep-red spectral range) pumped by a GaN diode laser at ∼442 nm. It employs a 0.8-mol% PrF3-doped ZBLAN double-clad fiber with a 7.5-µm core, a double D-shaped inner cladding, and a length of 3.0 m. The laser delivers a maximum output power of 0.71 W at 716.7 nm with a slope efficiency of 9.0% (versus the launched pump power) and a laser threshold of 0.90 W. The laser emission is partially polarized. The laser performance is simulated providing a guideline for watt-level deep-red fiber laser sources.

High-Power Multi-Wavelength Double-Clad Erbium Ytterbium Co-Doped Fiber Laser Using Two-and Four-Mode Fiber Filters

This work demonstrated a multiwavelength erbium-ytterbium co-doped double-clad fiber laser using two- (TMF) and four-mode fibers (FMF) as comb filters. At the maximum pump power of 9 W, the multi-wavelength fiber laser (MWFL) using the TMF filter generated 4 stable lasing lines with a spacing of 0.56 nm. The maximum output power recorded for this setup was as high as 553 mW with a 6.4% slope efficiency. Meanwhile, MWFL uses FMF filter generated 3 lasing lines with a spacing of 0.95 nm. The laser had a maximum output power of 443 mW with a slope efficiency of 5.3%. Both MWFLs were stable when operated for an extended period. The long-term stability test shows that the laser had only small wavelength drifts of 0.21 nm and 0.15 nm using the TMF and FMF filters, respectively. The maximum power fluctuations of the lasing lines were measured to be 2.10 dB for the MWFL using the TMF filter and 2.52 dB using the FMF filter. This work proposed stable high-power MWFL with higher output power and efficiency.

Dark Rectangular Pulses From a Dumbbell-Shaped Mode-Locked Double-Clad Er:Yb Laser

The formation of dark rectangular pulses from a dumbbell-shaped mode-locked double-clad erbium-ytterbium fiber laser is experimentally demonstrated. The laser operates under a large net-anomalous cavity dispersion regime, with a passive mode locking mechanism that relies on a nonlinear amplifying loop mirror (NALM) along with a nonlinear optical loop mirror (NOLM). This design facilitates the control of nonlinear effects within the cavity and enables the generation of dark pulses as the dominant mode locking regime. The variations of dark-rectangular pulse emission and its spectral evolution are experimentally investigated as a function of the pump power, revealing a dependence analogous to bright dissipative soliton resonance (DSR) pulses, where the dark pulse duration increases with increasing pump power, a behavior that is opposite to previously reported dark rectangular pulses. At the maximum pump power of 9.5 W, the mode-locked fiber laser generates dark rectangular-shaped pulses with duration of 571 ns, average output power of 600 mW, fundamental repetition rate of 320 kHz.

High-power tunable red laser based on double-cladding Pr3+-doped fiber

A high power visible laser is produced by combining double-cladding fluoride fiber, a specially fiber structured suitable for high power visible laser generation. Here, a double-cladding Pr3+-doped red fiber laser with an output power of 3.65 W and slope efficiency of 22 % had been developed in this research, making it the highest output power ever obtained in fiber lasers. In addition, the first tunable double-cladding fiber laser was also created, with a tuning range of near 9 nm from 632.60 nm to 641.48 nm. The free-running laser also achieved more than 500 mW at the center wavelength of 636.38 nm. With this tunable laser, new ground is broken in the field of double-cladding fiber tuning.

High power passively mode-locked laser with Sb2Te3 deposited tapered fiber in Er/Yb doped fiber laser

Antimony telluride (Sb2Te3), one of the materials from the topological insulator (TI) family, was studied as a saturable absorber (SA) for producing high-power ultrafast lasers in the C-band region. In order to achieve a mode-locked operation, a tapered fiber with a tapered waist of 6 μm was coated with Sb2Te3 to provide the interaction of the evanescent field with the material. Non-linear optical properties of the constructed SA include a 4.05 % modulation depth and a saturation intensity of 0.35 MW/cm2. Mode-locked pulses were generated when the SA was placed inside the cavity. The mode-locked pulses were solitonic, having a center wavelength of 1561.5 nm and a pulse duration of 1.8 ps at a pump power of 461 mW. The fundamental frequency measured was 18 MHz within pump power ranging from 461 mW to 657 mW. The maximum average output power, pulse energy, and peak power obtained from the generated mode-locked pulses were 269 mW, 14.9 nJ, and 8.3 kW, respectively. The measured signal to noise (SNR) of 55 dB indicates the excellent stability of the mode-locked pulses. This is the first demonstration of mode-locked pulses utilizing Sb2Te3 coated tapered fiber as an SA in a double-clad erbium-ytterbium doped fiber (DC-EYDF) laser cavity that we are aware of.

(INVITED)Tm:YAG crystal-derived double-clad fibers – A hybrid approach towards high gain and high efficiency Tm lasers

The hybrid approach of combining a Tm:YAG laser crystal with an amorphous fused silica tube is investigated to evaluate the suitability of the resulting crystal-derived fibers for efficient double-clad fiber lasers. The fabrication process and fiber properties of these Tm fibers are investigated, focusing on the dependence of the active fiber properties on the incorporated Tm3+ concentration. Crystal rods with different doping concentrations (TmxY1-x)3Al5O12 (x = 0.02, 0.05 and 0.08) were used as starting core material for fiber drawing. The investigated fibers are mechanically stable and result in a fairly homogenous and amorphous core glass with optical absorption and emission spectra that are similar to conventional Tm:Al doped silica fibers. Regarding laser properties with 790 nm cladding pumping, we could achieve a maximum slope efficiency of 47% with an output power of 4 W. The fiber laser results are compared to a conventionally fabricated double-clad Tm fiber prepared by Modified Chemical Vapor Deposition and solution doping. To the best of our knowledge, we demonstrate the highest laser output and the highest efficiency obtained from a Tm:YAG crystal-derived fiber.

Various pumping modes of high-power double clad fiber laser

As one of the first invented laser categories, fiber laser plays a crucial role in many specific fields, e.g., filed-optic communication, sensing, industrial processing, national defense, military. In order to effectively couple the pump light into the single-mode fiber, double-clad fiber laser was invented, i.e., the power and efficiency of fiber lasers have been significantly improved. There are two mainly categories of pumping mode for double clad fiber laser, named as end smoothing the gain curve pumping and side pumping. This paper will focus on the analysis and comparison of these two pumping modes in terms of the power, efficiency, relative population density, thermal load and feasibility. The experimental procedure will be achieved based on the MATLABR2021b and SFTool. The aim of the paper is to investigate the effects on the forward pumping and backward pumping in the process of side pumping and end pumping. According to the analysis, side pumping and bi-direction pumping smooth the gain curve effectively. Choosing appropriate pumping mode can reduce the loss and save the cost of optical transmission to a large extent. These results shed light on selection of pumping mode for high power fiber laser.

Generation of unconventional burst-pulse bundle in ytterbium-doped double-clad fiber laser based on self-mode-locked and double passively Q-switched technologies

We experimentally demonstrate the unconventional burst-pulse bundle generation in a linear-cavity ytterbium-doped double-clad fiber laser based on self-mode-locked and double passively-Q-switched technologies. When the pump power is 4421.0 mW, we obtained the burst pulse bundle with proportional pulse qualities. The full width at half maximum (FWHM) of the burst pulse is 2.2 μs, the time interval between the adjacent burst pulse is 2.4 μs and the energy of a single burst pulse is 0.62 μJ. In addition, the maximum burst-pulse energy is 0.85 μJ at the pump power of 4574.0 mW, the minimum FWHM and time interval are 1.7 and 1.4 μs at the pump power of 5387.0 mW. The formation mechanism of the unconventional burst pulse bundle is also discussed in detail.

Flat and Broadband Pulse Generated in an Er/Yb Co-Doped Double-Clad Fiber Laser

Flat and Broadband Pulse Generated in an Er/Yb Co-Doped Double-Clad Fiber Laser

All-fiber wavelength-widely tunable multi-pulse gain-switched Tm3+-doped double-clad fiber laser

We report a wavelength-widely tunable multi-pulse gain-switched Tm3+-doped fiber laser. The laser has a continuous wavelength-tunable range of 105 nm in 2 μm band. The combination of Tm3+-doped double clad fiber and 793 nm pulsed pump source achieves large-energy pulse and multi-pulse operation. The single-pulse energy can reach 4.3 μJ and the multi-pulse energy can be 13.2 μJ. The effects of pump pulse energy, pulse repetition rate and pulse duration on multi-pulse generation are studied in detail. This easy-to-operate large-energy 2 μm pulsed fiber laser with adjustable pulse duration and repetition rate can provide a stable single-pulse or multi-pulse source in spectroscopy, medical surgery, material processing, etc.

Direct Generation of 7 W, 360 μJ Multi-Pulse Laser From an Ultra-Compact All-Fiber Gain Switched Tm³+-Doped Double-Clad Fiber Laser

We report on the investigation of multi-pulse Tm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped double clad fiber laser (TDCFL) with an ultra-compact four devices-based all-fiber structure. This multi-pulse is implemented by the long relaxation time of gain-switched process. The number of pulse in a pulse cluster can be tuned from 1 to 8 by changing the pump pulse energy. With laser cavity design (i.e. large laser output coupling ratio and high gain mutual balance), the multi-pulse laser can finally generate an average output power of 7.25 W with corresponding pulse energy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$362.5~\mu \text{J}$ </tex-math></inline-formula> . The 2017 nm multi-pulse TDCFL has a high laser conversion efficiency of ~30% and the good operation stability with signal to noise ratio (SNR) of 77 dB. The experimental results would be fruitful to the communities interested in all-fiber multi-pulse lasers.

Low repetition rate gain-switched double-clad thulium-doped fiber laser operating in the 2 µm wavelength region

The experimental demonstration of a gain-switched pulsed fiber laser with low repetition rate emission in the 2 µm wavelength region is presented. The laser cavity is based on the figure-9 shape, where the gain-switched operation of the laser is obtained by using a double-clad Tm-doped fiber (DCTDF) as gain medium and a commercial pulsed laser diode at 793-nm with configurable parameters as pump source. The pulse parameters of the pump source are optimized for efficient suppressing of unstable gain-switched laser oscillations. As a result, laser pulses with low repetition rate in a range from 10 to 20 kHz with laser emission at the wavelength of 1951 nm are obtained. The generated gain-switched pulses exhibit maximum duration and energy of 0.5 and 3.5 µJ, respectively. The delay time between the pump pulses and the gain-switched pulses is of ~ 0.5 µs.

Self-mode-locking and self-phase modulation in Tm3+-doped double clad fiber laser for pulse peak power enhancement and multi-wavelength generation

A dual frequency mode-locked Tm3+-doped double clad fiber laser (TDCFL) is proposed by combining self-mode-locking with self-phase modulation (SPM) effect. The SPM effect stimulates the 24th harmonic mode-locking operation. The unpumped gain fiber-based self-mode-locking effect initiates the fundamental mode-locked operation. This fundamental mode-locked pulse acts as a modulation envelope of the 24th harmonic one. In this situation, the maximum pulse peak power and the largest pulse energy improve greatly. Its maximum pulse peak power is at least 311 times higher than the fundamental mode-locked one. And the difference of pulse energy is ~7.8 times. Furthermore, this dual frequency mode-locked TDCFL generates multi-wavelength light under high pump power. These results could offer an exciting new prospect for obtaining simple, compact and high performance multi-wavelength mode-locked fiber lasers.

Tunable synchronized dual-wavelength pulsed operation in an Er/Yb double-clad fiber laser

We present a simple and efficient experimental approach to synchronized dual-wavelength pulsed operation in an all-fiber laser. Four different dual-wavelength emissions of synchronized picosecond pulses are generated through simple adjustments of a wave retarder. Autocorrelation traces exhibit modulation profiles corresponding to dual-wavelength emissions with wavelength separations ranging over one order of magnitude, from 0.96 to 9 nm. In all cases, it is observed stable dual-wavelength operation and perfect synchronization between both pulsed components, without requiring of intra-cavity dispersion management. For the first time, to the best of our knowledge, synchronous tunable dual-wavelength pulse emission in a single-cavity Er/Yb double clad ring fiber laser is experimentally demonstrated.

Multiple mode-locked regimes of an Er/Yb double-clad fiber laser based on NPR

In this paper, we experimentally demonstrate generation of diverse structures of robust optical pulses obtained with a ring cavity passively mode-locked fiber laser based on a double-clad erbium-ytterbium doped fiber, and operating at net-anomalous cavity dispersion. A half-wave and a quarter-wave retarder plates allow adjustable saturable absorbing action by the nonlinear polarization rotation technique. Pulsed laser operation in quasi- continuous wave, molecules of solitons, and single-wavelength noise-like pulses (NLPs) regimes is obtained by properly adjusting the wave retarders. In the soliton and NLPs operating regimes, the central laser wavelength lies in the 1540 nm region. The obtained NLPs exhibit narrow peak coherence of ∼231 fs.