Ytterbium-doped Double-clad Fiber Laser Research Articles

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

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.

All fiber normal dispersion mode locked ytterbium doped double-clad fiber laser using fiber taper with WS2-ZnO saturable absorber

Efficient and stable mode-locking operation at 1075 nm is demonstrated in a double-clad ytterbium-doped fiber laser (DC-YDFL) with WS2-ZnO deposited on a fiber taper as a saturable absorber (SA). The WS2-ZnO composite is prepared by a simple and cost-effective heating method and deposited onto the fiber taper before being incorporated into the laser cavity. A high power mode-locked normal dispersion output at 1075 nm with a 3 dB bandwidth, repetition rate, pulse width and pulse energy of 3.7 nm, 10.98 MHz, 459 fs and 139.3 nJ respectively are obtained at a pump power of 3.65 W. Due to the interaction of the WS2-ZnO nanoparticles with the evanescent field of the propagating signal instead of directly, the SA has a higher laser damage threshold, therefore allowing for higher pulse powers to be obtained.

Highly Efficient Holmium-Doped All-Fiber ∼2.07-μm Laser Pumped by Ytterbium-Doped Fiber Laser at ∼1.13 μm

We report a 2.07-μm Holmium-doped all-fiber laser (HDFL) pumped by a 1.13-μm Ytterbium-doped fiber laser (YDFL). Home-made alumino–germano–silicate holmium-doped fiber (HDF) served here as an active medium, optimized in terms of chemical composition and co-dopants’ concentrations. Laser action at 2.07 μm was assessed in simple Fabry–Perot cavity, formed by a couple of home-made fiber Bragg gratings (FBGs), inscribed directly in the HDF; this allowed notable diminishing of intracavity loss of the 2.07-μm laser. HDF was in-core pumped by the 1.13-μm double-clad YDFL with a power of ∼12.5 W, in turn pumped in-clad by a laser diode (LD) operated at 0.97 μm with ∼24.5-W output. Using optimal length (∼5.0…5.5 m) of the HDF and employing FBG couplers with reflections of ∼99% and ∼33%, the HDFL provided ∼5.0-W output at 2.07 μm. At these conditions, maximal absolute (slope) efficiencies at 2.07 μm of 39% (42%) and 20% (22%) were measured with respect to 1.13-μm (YDFL) and 0.97-μm (LD) pumps, respectively. Moreover, the record slope efficiency (48%) was obtained for the powers ratio of 2.07-μm output (HDFL) to launched 1.13-μm input (YDFL), which is only slightly less than theoretical quantum efficiency limit (53%) for this kind of pump schemes.

An Adjustable EIT-Based FBG in Yb:silica Master-Oscillator Fiber Power-Amplifier System

An adjustable continuous-wave single-mode double-clad ytterbium-doped silica fiber laser is numerically investigated in the form of a master-oscillator fiber power-amplifier array. An optically-tunable coupler is suggested based on the nonlinear electromagnetically induced transparency (EIT) within fiber Bragg grating. Here, the Si nanocrystals is embedded in SiO2 over the selected regions of the output coupler. The transmittance is adjusted using a low power control field by modulating the refractive index in the EIT material.

Q-switched double-clad Ytterbium-doped fiber laser using MoS2 flakes saturable absorber

By sandwiching MoS2 thin flakes between two fiber ferrule connectors in the ring cavity, we successfully demonstrate the passive Q-switched fiber laser operation. The cavity consists of all-fiber double-clad ytterbium-doped fiber (YDF) as a gain medium and MoS2 tape as a saturable absorber (SA). The SA was prepared from a commercial MoS2 crystal (~ 99.8 % purity) through mechanical exfoliation process. A piece of 1 mm x 1 mm tape contains MoS2 thin flakes was sandwiched between two fiber connectors. By controlling loss and gain in the cavity, stable Q-switching operation were generated. The repetition rate was tunable from 4.8 kHz to 17.2 kHz as the pump power is varied from 753 mW to 1133 mW. The obtained pulse width is also narrowed from 21.3 µs to 10.44 µs with the same variation of pump power.

Generation of Mode-Locked Ytterbium Doped Fiber Ring Laser Using Few-Layer Black Phosphorus as a Saturable Absorber

We demonstrate the generation of mode-locked pulses from a double-clad ytterbium-doped fiber laser (YDFL) employing a saturable absorber (SA) made of a few layers of black phosphorus (BP). The BP SA was prepared by mechanically exfoliating BP crystal and spreading the acquired BP flakes on a piece of scotch tape. The tape was then sandwiched between two ferrules and incorporated in a YDFL cavity to achieve a stable mode-locked operation at 1085.58 nm with a repetition rate of 13.5 MHz. A maximum pulse energy of 5.93 nJ was obtained at pump power of 1322 mW with the output power of 80 mW. Our study may well be the first demonstration of the BP-based mode-locked fiber laser that should shed some new insights into two-dimensional layer materials related photonics.

Molybdenum Disulphide Tape Saturable Absorber for Mode-Locked Double-Clad Ytterbium-Doped All-Fiber Laser Generation**Supported by the PPP Grant Scheme of University of Malaya under Grant No PG098-2014B.

We demonstrate the generation of passive mode-locked double-clad ytterbium-doped fiber laser operating in a 1-micron region. We prepare the saturable absorber from commercial crystal of molybdenum disulphide (MoS2). Without chemical procedure, the MoS2 is mechanically exfoliated by using a clear scotch tape. A few layers of MoS2 flakes are obtained on the tape. Then, a piece of 1 × 1 mm tape containing MoS2 thin flakes is inserted between two fiber ferrules and is integrated in the ring cavity. Stable mode-locking operation is attained at 1090 nm with a repetition rate of 13.2 MHz. Our mode-locked laser has a maximum output power of 20 mW with 1.48 nJ pulse energy. These results validate that the MoS2 has a broad operating wavelength which covers the 1-micron region, and it is also able to work in a high-power cavity.

Generation of Mode-locked Ytterbium doped fiber ring laser using few-layer black phosphorus as a saturable absorber

We demonstrate the generation of mode-locked pulses from a double-clad ytterbium-doped fiber laser (YDFL) employing a saturable absorber (SA) made of a few layers of black phosphorus (BP). The BP SA was prepared by mechanically exfoliating BP crystal and spreading the acquired BP flakes on a piece of scotch tape. The tape was then sandwiched between two ferrules and incorporated in a YDFL cavity to achieve a stable mode-locked operation at 1085.58 nm with a repetition rate of 13.5 MHz. A maximum pulse energy of 5.93 nJ was obtained at pump power of 1322 mW with the output power of 80 mW. Our study may well be the first demonstration of the BP-based mode-locked fiber laser that should shed some new insights into two-dimensional layer materials related photonics.

Comparison between threshold and sensitivity of stimulated Brillouin scattering at different pumping configurations in high-power double-clad fiber lasers

Theoretical analysis of stimulated Brillouin scattering (SBS) in high power ytterbium-doped double-clad (YDDC) fiber lasers is presented by solving the steady-state rate equations with regard to SBS at different pumping configurations. The behavior of Brillouin Stokes power growth along the fiber is investigated and the SBS threshold power is quantitatively compared at forward, backward and bi-directional pumping configurations. It is shown that the backward pumping configuration has higher SBS threshold power than two others. Also. The effect of cavity parameters such as cavity length, front mirror reflectivity, dopant concentration and laser linewidth at different pumping configuration have been studied. It can be seen although the backward puming has higher SBS threshold but its sensitivity to cavity parameters is higher than other pumping configuration which is a negative impact for cavity designing.

First experimental investigation of the amplification of a Yb-doped fiber laser pumped with 1000 and 1014-nm laser diodes

We present two preliminary experimental investigations of the amplification of a 1064-nm master oscillation power amplification configuration ytterbium-doped double-clad fiber laser pumped with two new-wavelength pump sources, namely 1000 and 1014-nm laser diodes. The power output of the amplified signal reached 4.8 W pumped at 1000 nm and 2.708 W at 1014 nm with an extraction efficiency of 42.6 and 29.8 %, respectively. Combined with simulations, the experimental results also indicate that the efficiency of the amplification can be further improved with a higher pump power. To the best of our knowledge, we report, for the first time, amplification pumped using 1000 and 1014-nm sources.

Self-pulsing in a large mode area, end-pumped, double-clad ytterbium-doped fiber laser

The characteristics of self-pulsing in a large mode area, end-pumped, double-clad Yb-doped fiber laser are presented. The laser operates in a self-pulsing regime, either by using one or two perpendicularly cleaved ends as the feedback mirrors, while it transforms in a broadband amplified spontaneous emission source when both ends are angle cleaved. In the pulsed regime, up to 2 µs full width at half maximum pulse widths and repetition rates of the order of hundreds of kHz are generated.

Numerical analysis of Ytterbium-doped double-clad fiber lasers based on the temperature-dependent rate equation

The effects of temperature on the output power and optimal conditions of Ytterbium-doped double-cladding fiber lasers (YDDFLs) are discussed. Temperature-dependent rate equations for YDDFLs based on Boltzmann distribution are built in two-end pump model. The results show that the output power and the slope efficiency decrease with the increase of temperature. The increase of pump power results in that the effect of the temperature on the output performance increases, and the fiber length is a factor that the effect of the temperature depends on really. Moreover we combine the heat distribution formula with the rate equations and compare the numerical results considering with that not considering the temperature-dependence inside laser cavity, the effect of temperature can be ignored only when the pump power is lower, and the optimal fiber length becomes longer when considering the temperature-dependence.

A combined algorithm for simulating fiber lasers based on the shooting and relaxation methods

The characteristics of the shooting and relaxation methods for solving the model of an ytterbium-doped double-clad fiber laser are discussed in detail by comparing their accuracies. Accordingly we propose a combined algorithm by taking advantage of the merits of both methods, which can automatically adjust initial trial values in calculations according to the desired requirement of accuracy. The results for verifying the efficiency and reliability of our proposed algorithm show that the level of accuracy and speed can completely satisfy the conventional requirements of numerical simulations.

Experimental Investigation on 1018-nm High-Power Ytterbium-Doped Fiber Amplifier

We present an all-fibered 1018-nm ytterbium-doped double-clad fiber laser in master oscillation power amplification configuration. The output characteristics of 1018-nm laser with seed power, gain fiber length, and fiber type are experimentally investigated. The power of the seed laser needs to be much higher to suppress amplified spontaneous emission and enable the sufficient amplification of the 1018-nm seed laser than the case of 1080-nm amplification. And the requirement of the seed power increases with the gain fiber length. The experimental results also indicate that gain fiber with large pump fill factor and low Yb ion concentration is more appropriate for the high-power 1018-nm fiber laser. With this gain fiber, we demonstrate a 77-W near diffraction limited fiber amplifier emitting at 1018 nm with power conversion efficiency of 75%.

Investigation of self-pulsing and self-mode-locking in ytterbium-doped fiber laser

The output characteristics of a continuous-wave diode pumped free-running double-clad ytterbium-doped fiber laser are investigated. In the experiment, not only self-pulsing is observed, but also self-mode-locking is observed for the first time in the free-running fiber laser. The physical mechanism responsible for these phenomena is analyzed. The analysis reveals that the signal is absorbed in the weakly pumped or non-pumped part of the active fiber, which leads the self-pulsing to be present, and self-mode-locking is induced by axial mode beating and self-phase modulation, which are enhanced by nonlinear effects, stimulated Raman scattering, and stimulated Brillouin scattering. The pulse width of self-pulsing decreases as pump power increases. The pulse width of self-mode-locking pulses becomes narrow with the increase of the pump power. When the pump power is higher than 8 W, self-pulsing and self-mode-locking disappear. The interval between adjacent self-mode-locking pulses is 224 ns, corresponding to the cavity round-trip time. The maximum and the minimum durations (full width at half maximum) of self-mode locked pulses are about 35.0 ns and 6.3 ns respectively, and the maximum and minimum spectral widths (full width at half maximum) of signal light are about 7.05 nm and 2.01 nm respectively.

Tunable double-clad ytterbium-doped fiber laser based on a double-pass Mach–Zehnder interferometer

We have demonstrated an adjustable double-clad Yb 3+-doped fiber laser using a double-pass Mach–Zehnder interferometer. The laser is adjustable over a range of 40 nm from 1064 nm to 1104 nm. By adjusting the state of the polarization controller, which is placed in the double-pass Mach–Zehnder interferometer, we obtained central lasing wavelengths that can be accurately tuned with controllable spacing between different tunable wavelengths. The laser has a side mode suppression ratio of 42 dB, the 3 dB spectral width is less than 0.2 nm, and the slope efficiencies at 1068 nm, 1082 nm and 1098 nm are 23%, 32% and 26%, respectively. In addition, we have experimentally observed tunable multi-wavelengths lasing output.

Backward pumping kilowatt Yb3+-doped double-clad fiber laser

A ytterbium-doped double-clad fiber laser generating up to 1026 W of continuous-wave output power at 1085 nm with a slope efficiency of 74% by single-ended backward pumping configuration is reported. The core diameter was 20 μm with a low numerical aperture of 0.06, and a good beam quality (BPP < 1.8 mm mrad) is achieved without special mode selection methods. No undesirable roll-over was observed in output power with increasing pump power, and the maximum output power was limited by the available pump power. The instability of maximum output power was better than ±0.6%. Different pumping configurations were also compared in experiment, which shows good agreements with theoretical analyses.

Comparative study of the output characteristics of ytterbium-doped double-clad fiber lasers with different pump schemes

The output characteristics of ytterbium-doped double-clad fiber lasers (YDCFLs) with different pump schemes are compared numerically in detail. The results show that the backward pumped YDCFL with pump reflection for double-pass scheme has the highest conversion efficiency, the most suitable for saving pump powers. As a result of the maximum output power per meter occurring in the forward pumped YDCFL with pump reflection, it means that this kind of pump scheme is preferable for saving YDCF lengths. Moreover, the output characteristic of the bi-directional pumped YDCFL is between forward and backward pumped ones.

Research on the characteristics of the Q-switched ytterbium-doped fiber lasers

Fiber lasers with pulse duration and repetition tuned have great application in space probe. On the basis of typical Q-switched ytterbium-doped double-clad fiber lasers under forward pump,the ion population and propagation equations for both pumping and signal light are presented, and the steady-state solution of inversion ion population, pumping power distribution and signal power distribution due to ASE are studied by the traveling-wave method. Moreover, the effects of fiber-laser parameters such as Yb-doped fiber length, pump power and fiber core diameter on pulse characteristics are analyzed.