Ytterbium-doped Fiber Laser Research Articles

Hundred-watts-level monolithic narrow linewidth linearly-polarized fiber laser at 1018 nm

We theoretically and experimentally demonstrated an all-fiber, hundred-watts-level, linearly-polarized, narrow spectral linewidth laser amplifier at a central wavelength of 1018 nm based on master oscillator-power amplifier configuration, which is composed of a laser oscillator and one stage of the fiber amplifier. The laser system can generate 104-W output power with 3- and 20-dB spectral linewidth of ∼0.073 and ∼0.25 nm, respectively, and a higher polarization extinction ratio of ∼17.89 dB at 1018.3 nm was obtained. Theoretical analysis based on the rate equations was used to optimize the parameters of 1018-nm ytterbium-doped fiber laser system for the maximum suppression of amplified spontaneous emission (ASE). The ASE was well depressed based on the optimization for the parameters of the laser system including the seed power, seed spectrum, gain fiber length in the amplifier, etc. And ∼ 27-dB signal-to-noise ratio was achieved at the maximum output power. The slope efficiency for the amplifier stage can reach 79%, and near-diffraction-limited beam quality ( M x 2 ∼ 1.617 and M y 2 ∼ 1.635 ) was obtained.

Single- and dual-wavelength switchable mode-locked dissipative soliton Yb-doped fiber laser based on graphene/WS2 nanocomposites modelocker and polarization controller

We report a single- and dual-wavelength switchable mode-locked dissipative soliton in an ytterbium-doped fiber laser based on graphene/WS2 nanocomposites saturable absorber. The graphene/WS2 nanocomposites film possesses efficient saturable absorption characteristics with large modulation depth (45.1%), which results in the stable single-wavelength mode-locking operation with pulse duration of 450 ps. By carefully rotating the polarization controller, the mode-locking operation can be switched to a dual-wavelength at both 1066.4 nm and 1069.2 nm due to the modulation of the intracavity birefringence. Our work extends the studies for 2D nanomaterials and supplies potential applications in the multi-wavelength fiber laser.

Tunable and switchable triple-wavelength ytterbium-doped fiber ring laser based on Sagnac interferometer with a polarization-maintaining photonic crystal fiber

A tunable and switchable triple-wavelength ytterbium-doped fiber laser (YDFL) based on a polarization-maintaining photonic crystal fiber (PMPCF) Sagnac interferometer is proposed and experimentally demonstrated. Owing to the large inhomogeneity of gain profile and simple two-level system of ytterbium-doped fiber, a tunable triple-wavelength lasing output is achieved with a tuning range of 1.6 nm. At room temperature, the maximum wavelength shift and peak power fluctuation are less than 0.018 nm and 0.64 dB, respectively. Moreover, the output lasing can be switched to single-wavelength lasing or dual-wavelength lasing through adjusting polarization controller. A tunable single-wavelength lasing with the side-mode suppression ratio above 50 dB is achieved from the wavelength of 1034.276 nm to 1038.314 nm. Two kinds of tunable dual-wavelength lasing with the tuning range of 3.2 nm are obtained in our experiment. In addition, the temperature stability is discussed by constructing the YDFL with PMPCF and conventional polarization-maintaining fiber (PMF), respectively. Experimental results demonstrate that the measured temperature sensitivity for PMPCF-based YDFL is 0.014 nm/℃, which is five times lower than that for PMF-based YDFL.

Experimental study of transverse mode instability threshold dependence on seed wavelength in high power ytterbium-doped fiber amplifiers

As the output power increases, the transverse mode instability (TMI) has become a major limitation for power scaling of high power fiber lasers with nearly diffraction-limited beam quality. Many strategies in experimental or theoretical scopes have been proposed to mitigate the TMI. Theoretical studies have indicated that the TMI thresholds of the laser amplifiers are affected by the seed laser wavelength. In this work, the influences of seed wavelengths on the TMI threshold in high power large-mode-area ytterbium-doped fiber (YDF) amplifiers based on an all-fiber master oscillation power amplifier structure are investigated experimentally. The TMI characteristics and thresholds of the same fiber amplifier seeded by respective 1080 nm, 1070 nm, and 1065 nm fiber lasers are analyzed and compared. The experimental results show that the TMI threshold decrease with the seed wavelength in the region of 1065 nm–1080 nm. For every 5 nm decrease in seed wavelength, the TMI threshold power can be increased by about 290 W. Compared with the fiber amplifier of the 1080 nm seed wavelength, the TMI thresholds of the 1070 nm and 1065 nm wavelength fiber amplifiers are respectively increased by around 58.7% and 86.2%. Reducing the wavelength of seed can effectively improve the TMI threshold, but the amplified spontaneous emission (ASE) and nonlinear effects are also enhanced. The results have significant guidance for the mitigation of TMI in high-power YDF laser systems.

Ytterbium-doped fiber laser as pulsed source of narrowband amplified spontaneous emission

We report random noise pulsed regime of an ytterbium-doped fiber laser arranged in common Fabry-Perot configuration. We show that the laser output obeys the photon statistics inherent to narrowband amplified spontaneous emission and that the noise pulsing is properly addressed in terms of probability density and autocorrelation functions. Our novel approach reveals, in particular, that the regime’s coherence time dramatically shortens, from few ns to tens ps, with increasing laser power.

In2Se3 nanosheets with broadband saturable absorption used for near-infrared femtosecond laser mode locking

Indium selenide (In2Se3) has attracted tremendous attention due to its favorable electronic features, broad tunable bandgap, high stability and other attractive properties. However, its further applications for nonlinear optics have not yet been fully explored. In this work, we demonstrate that few-layer α-In2Se3 nanosheets exhibit strong saturable absorption properties over a wide wavelength range covering 800, 1064 and 1550 nm. The few-layer α-In2Se3 nanosheets used for this experiment are fabricated via a simple ultrasonic exfoliation in liquid. Stable ultrafast mode-locking laser pulses are obtained from both ytterbium-doped and erbium-doped fiber laser systems operating at 1064 and 1550 nm, respectively. A pulse duration as short as 215 fs was achieved in the Er-doped fiber laser system. Stable output pulses over 6 h of operation were obtained in both laser systems. The pulse energy and peak power of the laser output pulses were increased by reducing the In2Se3 thickness. These results indicate that α-In2Se3 nanosheets with low layer numbers are promising candidates for broad ultrafast photonics devices, such as optical switchers, Q-switchers and mode lockers.

Passively mode-locked Yb-doped all-fiber oscillator operating at 979 nm and 1032 nm with the single wall carbon nanotubes as SA

We report on an all-fiber passively mode-locked ytterbium-doped (Yb-doped) fiber laser with single polymer composite saturable absorber (SA) based on the single wall carbon nanotubes (SWCNTs) with diameters of 0.8 nm. The SWCNTs are mixed with sodium carboxymethylcellulose (NaCMC) to form SWCNTs SA film. The non-saturable absorption coefficient, modulation depth and saturable intensity of the SWCNTs SA are measured to be 29%, 12% and 0.12 MW/cm2, respectively. By using the SWCNTs as SA, a passively mode-locked Yb-doped fiber laser has been achieved at 979 nm with pulse duration of 228 ps and repetition rate of 15.47 MHz. To our knowledge, this is the first time ever reported in an all-fiber Yb-doped mode-locked fiber laser using SWCNTs as SA at 980 nm, which overcome the difficulties of low gain and serious re-absorption effects in the quasi-three-level system. In order to verify the saturation absorption performance of the SWCNTs, mode-locking experiment in quasi-four-level system is also carried out around 1030 nm and the stable and uniform mode-locked pulses are obtained. A mode-locked fiber laser at 1032 nm is realized with a pulse width of 485 ps and repetition rate of 8.78 MHz. It is sufficiently manifested that SWCNTs with diameters of 0.8 nm have excellent saturable absorption performance as optical mode-locking elements in ultrafast photonic applications.

Radionuclide distribution during ytterbium doped fibre laser cutting for nuclear decommissioning

This article provides data on the radionuclide distribution during ytterbium doped fibre laser cutting of contaminated stainless steel in a simulated nuclear decommissioning scenario. Two stainless steel 25 mm thick plates labelled with Sr-85, Ru-106 and Tc-99, Cs-133 have been laser cut. In all experiments activity is mainly found within dross under the cut test piece and the material deposited within the local filtration system. No active Sr-85, Ru-106 or Tc-99 was analysed to be present on swabs made on the internal walls of the facility or obtained on the samples taken from the ventilation sample on the clean side of the facility HEPA filter during the active cutting trials. Conversely, Cs-133 has been measured in samples and swabs taken from throughout the laser cutting facility at decreasing concentrations correlating with the distance from the cut test piece(s).

Investigation of high temperature wear performance on laser processed nodular iron using optimization technique

Nodular cast iron (NCI) are used in nuclear energy and transportation industries. Also, NCI are used in gear boxes, camshaft, crank shaft, rolling mill rolls and machine tool beds. The reliability of the NCI under heavy loading condition is affected through several tribological aspects. In the present study, NCI surface has been melted by using an Ytterbium-doped fiber laser. The wear resistances of the substrate and melted surface have been analyzed by using a tribometer. Sliding speed, load and working temperatures have been considered as input parameters to tribometer. From the optimization trials, the applied load was identified as the most significant parameter followed by sliding speed and ambience temperature. The responses of the optimized tribological parameters attained by GRA was confirmed through experimental and agreed closely to the predicted value. Further, the surface of the substrate and laser melted samples were analyzed. The melted surfaces were free from surface deformities and exhibited a noticeable improvement in the wear resistance compared to the substrate.

Switchable and tunable multi-wavelength emissions in pulsed ytterbium fiber lasers with black phosphorus saturable absorbers and polarization-maintaining fiber Bragg gratings

In this paper, we present a systematic study of ytterbium-doped pulsed fiber lasers, both Q-switched and mode-locked, that emitted in switchable and tunable multi-wavelength states. The pulsed lasers were initiated by black phosphorus saturable absorbers (BP-SAs) prepared by an optically driven process. One relatively thicker BP-SA with a modulation depth of 16.8% and a saturable intensity of 13.09 MW/cm2 was used for Q switching, and one thinner BP-SA with a modulation depth of 6.7% and a saturable intensity of 7.82 MW/cm2 was used for mode locking. The switchable and tunable wavelength-emitting status was achieved by a Bragg grating written in polarization maintaining fibers (PM-FBG). The fabricated fiber Bragg grating had two reflection peaks. By adjusting an in-cavity polarization controller, the wavelength-emitting status of the pulsed lasers was flexibly switched in three discrete states: individual wavelength of 1063.8 and 1064.1 nm, respectively; and simultaneously emitting both wavelengths with tuning capability. Stable Q-switched and mode-locked laser pulses were observed with all three wavelength-emitting states. Furthermore, by applying stresses at the fast or slow axis of the utilized PM-FBG, the wavelength spacing could be tuned from 0.02 to 0.52 nm in the dual-wavelength emission state.

Q-switched fiber laser operating at 1 μm region with electron beam deposited titanium nanoparticles

We demonstrate the generation of Q-switched pulse train in Ytterbium-Doped Fiber Laser (YDFL) cavity by employing titanium (Ti) thin film as a passive saturable absorber (SA). The Ti-SA was fabricated by depositing Ti particles using electron beam evaporation on the surface of a polyvinyl alcohol (PVA) thin film. Subsequently, a stable Q-switching pulse train was successfully generated by introducing the Ti-SA into a laser cavity. The laser generated a self-starting pulse train with repetition rate that is tunable from 42.96 to 98.12 kHz as the 980 nm pump power is increased from 122.5 mW to 197 mW. At 197 mW pump power, the laser produced a Q-switching pulse train with pulse duration and pulse energy of 3.95 μs and 57.48 nJ, respectively. This demonstration proves that Ti-SA is suitable for generating Q-switched fiber laser. Furthermore, it is easy and cheap to fabricate.

Passively Q-switched Ytterbium-doped fiber laser based on broadband multilayer Platinum Ditelluride (PtTe2) saturable absorber

Two-dimensional (2D) layered Platinum Ditelluride (PtTe2), a novel candidate of group 10 transition-metal dichalcogenides (TMDs), which provides enormous potential for pulsed laser applications due to its highly stable and strong nonlinear optical absorption (NOA) properties. PtTe2 saturable absorber (SA) is successfully fabricated with firstly demonstrated the passively Q-switched laser operation within a Yb-doped fiber laser cavity at 1066 nm. Few layered PtTe2 is produced by uncomplicated and cost-efficient ultrasonic liquid exfoliation and follow by incorporating into polyvinyl alcohol (PVA) polymer to form a PtTe2-PVA composite thin film saturable absorber. The highest achieved single pulse energy is 74.0 nJ corresponding to pulse duration, repetition rate and average output power of 5.2 μs, 33.5 kHz and 2.48 mW, respectively. This work has further exploited the immeasurable utilization potential of the air stable and broadband group 10 TMDs for ultrafast photonic applications.

Cascaded harmonic generation from a fiber laser: a milliwatt XUV source.

Recent progresses in femtosecond ytterbium-doped fiber laser technology are opening new perspectives in strong field physics and attosecond science. High-order harmonic generation from these systems is particularly interesting because it provides high flux beams of ultrashort extreme ultraviolet radiation. A great deal of effort has been devoted to optimize the macroscopic generation parameters. Here we investigate the possibility of enhancing the single-atom response by producing high-order harmonics from the second, third and fourth harmonics of a turnkey 50 W, 166 kHz femtosecond Yb-fiber laser providing 135 fs pulses at 1030 nm. We show that the harmonic efficiency is optimal when the process is driven by the third harmonic, producing 6.6 ± 1.3 × 1014 photons/s at 18 eV in argon, which corresponds to 1.9 ± 0.4 mW average power.

Generation of Microsecond Ytterbium-Doped Fiber Laser Pulses using Bismuth Telluride Thin Film as Saturable Absorber

Bismuth telluride (Bi2Te3), a type of topological insulators, is currently in hot pursuit due to its unique physical properties. Therefore, this paper describes a simple Q-switched Ytterbium-doped fiber laser (YDFL) by using Bi2Te3 thin-film as saturable absorber. The few layers Bi2Te3 film was fabricated using optical deposition technique and subsequently, was used in an all-fiber, YDFL setup. As a result, a self-starting Q-switching pulses were first occurred when the laser pumping power reached 88.6 mW. As the pump power level increased, the observed pulses repetition rates had increased steadily from 17 to 29.63 kHz. Hence, this work demonstrated that Bi2Te3 thin-film can be used to successfully generate Q-switching pulses at 1-micron region and is well suited for many photonic applications operated at this wavelength region.

Q-switched ytterbium-doped fiber laser by using FIrpic as a saturable absorber

This work demonstrates a Q-switched ytterbium-doped fiber laser (YDFL) by using an organic material as a saturable absorber (SA). The organic material is FIrpic and it was embedded into polyvinyl alcohol (PVA) to form a thin film. The SA thin film was incorporated into the cavity to act as a Q-switcher. The Q-switching operation has a minimum pulse width of 2.4 µs at a central wavelength of 1067 nm. The maximum peak power and pulse energy were 193.9 mW and 465 nJ, respectively. The Q-switch operation was stable and showed a high signal to noise ratio of 66.4 dB. To the best of authors’ knowledge, this the first time that FIrpic has been used as a SA in the 1 µm region.

Dynamics of the passive synchronisation of erbium- and ytterbium-doped fibre Q-switched lasers with a common graphene saturable absorber

We have demonstrated a passively synchronized Q-switched erbium- and ytterbium-doped fibre laser by a common graphene saturable absorber (GSA), which generates optical pulses centered at 1530 nm and 1060 nm. The dynamics of the synchronisation of this laser have been studied. In this passively synchronized Q-switched laser, 1530 nm laser pulses affect the transmittance of 1060 nm light through the GSA and induce synchronisation of the two laser pulses. These experimental results have been explained by a simplified theoretical model of the dual-wavelength cross absorption modulation effect of a GSA. With the increase in the pump power, the repetition rate of synchronized pulses varies from 24. 51–39. 85 kHz, and the pulse widths of 1530 nm and 1060 nm vary from 6. 02–2. 41 μs and from 18. 79–3. 29 μs, respectively.

Mode-locked ytterbium-doped fiber laser based on offset-spliced graded index multimode fibers

We developed a passively mode-locked ytterbium-doped fiber laser based on offset-spliced graded index multimode fibers (OS-GIMFs), where OS-GIMFs play the role of saturable absorbers. The modulation depth of the saturable absorber is 15.28%, which significantly improves the performance of saturable absorber by adopting offset-spliced method. A stable mode-locked pulse train at 1040 nm with a 27.32 MHz repetition rate is generated when pump power reaches the threshold. The output pulse-width is a ∼11 ps and can be compressed to 980 fs by using a pair of gratings. The fiber laser is superior in terms of low cost, high damage threshold, and easy fabrication; thus, it has potential for application in ultrafast photonics and industrial processing.

Influence of few-layer WS2 and mono-layer WS2 on passively Q-switched ytterbium-doped fibre lasers

Q-switched Yb-doped fiber lasers based on few-layer WS2 and mono-layer WS2 were demonstrated in this paper. The modulation depths of few-layer WS2-polyvinyl alcohol film and mono-layer WS2-polyvinyl alcohol film were 21.1% and 25.9%, respectively. The shortest pulse durations of the two fiber lasers were 2.7 μs and 748 ns, respectively, and the maximum pulse energy was 205 nJ and 154.2 nJ. From the results, the pulse duration of the fiber laser with mono-layer WS2 is narrower than that of the laser with few-layer WS2, and the peak power of the pulse is higher than that of the laser employing few-layer WS2 owing to the large modulation depth of mono-layer WS2. To the best of our knowledge, 205 nJ is the largest pulse energy of Q-switched fiber lasers with TMDs at 1.0 μm waveband. The results illustrate that WS2 is one promising saturable absorber to achieve high energy output in fiber lasers.

Q-switched mode-locked ytterbium-doped fiber laser with radial polarization

A Q-switched mode-locked, radially polarized ytterbium-doped fiber laser was demonstrated. In the study, the combination of a c-cut YVO4 birefringent crystal and a single-lens was utilized as the intracavity polarization discriminator, and a semiconductor saturable absorber mirror was used as passive mode-locked element. A narrow band-pass filter was inserted into the cavity to stabilize the mode-locked pulses and lasing wavelength. At the absorbed pump power of 1.56 W, the output power was 202 mW, corresponding to slope efficiency of 22.8%. The repetition rate and width for Q-switched envelope were 60.5 kHz and 315 ns, respectively. The mode-locked pulses inside the Q-switched envelope had a repetition rate of 66.67 MHz, the pulse width of 163 ps and the largest single-pulse peak power of 975 W.

Yb-doped fiber laser mode-locked with Au nanocages/SiO2 saturable absorber

Au nanocages/SiO2 (Au-NCs/SiO2) are prepared through a seed-mediated growth method, and the performance is investigated in an all-fiber passively mode-locked ytterbium-doped fiber laser, for the first time. Its saturating intensity and modulation depth are measured to be about 0.461 MW/cm2 and 5.3%, respectively. With the Au-NCs/SiO2 saturable absorbers (SA) film, the pulse with the pulse duration of 1.116 ns and repetition rate of 32.02 MHz was generated at 1063.14 nm, under the pump power of 342 mW. And the corresponding average output power of 4.82 mW was obtained. These results indicate that Au-NCs/SiO2 has excellent saturable absorption properties with the potential for important applications in the field of ultra-short pulse lasers.