Q-switched Yb-doped Fiber Laser Research Articles

Single-mode operation and spectral depuration by W-type Yb-doped fibers in Q-switched fiber lasers

We report a W-type fiber design for improving the beam quality and spectral purity of the Q-switched Yb-doped fiber lasers (YDFLs). Our W-type fiber exhibited higher losses in the high order modes (>100 dB/m) and lower losses in the fundamental modes (<0.1 dB/m). A 20/130 μm Yb-doped W-type fiber was fabricated by employing a modified chemical vapor deposition (MCVD) process and a solution-doping technique. The Yb-doped W-type fiber was examined in an acousto-optic Q-switched YDFL. A robust single-mode operation with a 1.19 M2 factor was obtained by optimizing the bending radii. The suppression of mixed mode four-wave mixing (FWM) and amplified spontaneous emission (ASE) was observed in the output spectral with an 18 dB signal to noise ratio (SNR) enhancement at 1064 nm and a 5.3 dB ASE inhibition ratio at 1030 nm. The Yb-doped W-type fiber exhibited enhanced beam quality and output spectra than the conventional Yb-doped step-type refractive index fiber. Therefore the W-type fiber suits the Q-switched fiber laser applications.

Passively Q-switched Yb-doped fiber laser based on Ag nanoplates saturable absorber

We experimentally investigated Ag nanoplates as saturable absorber for Q-switched pulse generation in an Yb-doped fiber laser. The pulse train repetition rate increases with the increase of the pump power. At the maximum pump power of 600 mW, the maximum repetition rate and average output power are 184.8 kHz and 10.77 mW, respectively, corresponding to single pulse energy of 58.3 nJ. To the best of our knowledge, it is the first demonstration of the passively Q-switched fiber laser utilizing the material of Ag nanoparticles at the wavelength of 1-μm. Our investigations demonstrate the flexibility of our solution-processed Ag nanoplates-based saturable absorber, making it a promising candidate for a variety of stable and low-cost ultrafast lasers.

Q-switched ytterbium fiber laser based on rhenium diselenide as a saturable absorber

Rhenium diselenide (ReSe2) is a kind of VII-B transition metal dichalcogenides (TMDs) with a unique distorted 1T structure which is different from the VI-B TMDs (MoS2, WS2, MoSe2, WSe2, etc), resulting in its special optical properties. In this work, we proposed and demonstrated a passively Q-switched Yb-doped fiber laser using ReSe2 as a saturable absorber (SA). ReSe2 nanosheets were prepared by liquid phase exfoliation method and mixed with polyvinyl alcohol (PVA) to form a SA compatible with fiber. By inserting the ReSe2-PVA film into the two fiber ferrules of the fiber laser, a stable Q-switched operation at 1.06 µm was achieved. It had a maximum output power of 1.21 mW with a maximum pulse energy of 30.4 nJ and a minimum pulse duration of 2.27 µs. This work realizes a Q-switched fiber laser with stable performance based on the ReSe2 prepared using a low cost, simple and scalable method.

Wavelength-tunable LP11 mode pulse fiber laser based on black phosphorus

A wavelength-tunable LP11 mode Q-switched Yb-doped fiber laser was demonstrated based on black phosphorus. To the best of our knowledge, it’s the first time to achieve wavelength-tunable higher-order mode pulse laser output in the 1 μm region. The output central wavelength of this self-starting pulse laser can be tuned from 1054.4 nm to 1068.2 nm continuously in the LP11 mode state. The linewidths of different wavelengths were less than 0.12 nm. During the long-term operation, the central wavelength and bandwidth had no obvious change and the fluctuation of output power was less than 0.67%. This wavelength-tunable higher-order mode pulse laser showed excellent stability, and could be employed as a wideband source for optical and photonic applications.

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.

Passively Q-switched Yb-doped dual-wavelength fiber laser based on a gold-nanocage saturable absorber.

In this paper, we demonstrate a passively Q-switched Yb-doped dual-wavelength fiber laser using gold nanocages (GNCs) as a saturable absorber. The GNCs are prepared by the seed-mediated method with modulation depth of 5.3% and saturable intensity of 0.16 MW/cm2. A simultaneous dual-wavelength operation is achieved at 1059.9 and 1060.5 nm with 3 dB bandwidths of 0.05 and 0.04 nm, respectively. A maximum average output power of 6.03 mW with minimum pulse width of 2.06 μs and maximum repetition rate of 134.9 kHz is obtained at a pump power of 385 mW, corresponding to optical-to-optical conversion efficiency of 1.57% and slope efficiency of 2.75%.

High-power passively Q-switched Yb-doped fiber laser based on Tin selenide as a saturable absorber

In this paper, tin selenide (SnSe2) is proposed as a saturable absorber (SA) for demonstrating a dual-wavelength passively Q-switched Yb-doped fiber laser. A film-type SnSe2-PVA SA was successfully prepared by incorporating the SnSe2 nanosheets with the polyvinyl alcohol. The nonlinear absorption properties of the SA were investigated within a Yb-doped fiber laser. Stable passively Q-switched pulse operation with a maximum output power of 18.03 mW under pump power of 680 mW was generated, and the minimum pulse duration was 966 ns under a pulse repetition rate of 168.7 kHz, corresponding to a pulse energy of 106.9 nJ. Thereinto, 18.03 mW, 168.7 kHz and 966 ns were all the recorded parameters obtained within a 2D material-based passively Q-switched ring-cavity Yb-doped fiber laser. The excellent results proved that SnSe2 has well-matched nonlinear absorption properties in comparison with other reported transition metal dichalcogenides, Thus, wide-ranging important potential applications of SnSe2 in the field of ultrafast optics will soon be recognized.

Mo0.5W0.5S2 for Q-switched pulse generation in ytterbium-doped fiber laser

In this work, we fabricate the Mo0.5W0.5S2 by microwave-assisted solvothermal method, and report the Q-switched Yb-doped fiber lasers (YDFL) using Mo0.5W0.5S2 polymer film and tapered fiber as the saturable absorbers (SAs). The modulation depth and saturable intensity of the film SA are 5.63% and 6.82 MW cm−2. The shortest pulse duration and the maximum single pulse energy are 1.22 μs and 148.8 nJ for the film SA, 1.46 μs and 339 nJ for the fiber-taper SA. To the best of our knowledge, this is the first report on the Q-switched YDFL using Mo0.5W0.5S2 SAs.

Radially polarized and passively Q-switched Yb-doped fiber laser based on intracavity birefringent mode discrimination

In this paper, we demonstrated a passive Q-switched ytterbium-doped fiber laser with radially polarized beam emission by using a c-cut YVO4 birefringent crystal as the intracavity polarization discriminator, and a Cr4+:YAG crystal as the saturable absorber and output coupler. The maximum averaged laser power reached 3.89 W with a high slope efficiency of 66.5%. The laser pulse had a peak power of 161 W, 160 ns duration, and 151 kHz repetition rate at the absorbed pump power of 6.48 W. Such a radially polarized pulse would facilitate numerous applications.

Passively Q-Switched Yb-Doped All-Fiber Laser With a Black Phosphorus Saturable Absorber

We report two kinds of Q-switched Yb-doped fiber lasers based on a black phosphorus saturable absorber (BP-SA). The BP-SAs are prepared by two different methods, one of which is the mechanical exfoliation method and the other is the liquid-phase exfoliation method. The BP-SAs are inserted into the all-fiber Yb-doped oscillation cavity in different forms. We have experimentally shown that the passively Q-switched pulse trains could be obtained by the two methods. First, we achieve the Q-switched pulse in 1029.63 nm by using a few-layer black phosphorus sheet. The fiber laser was capable of generating pulses with a maximum average output power of 13.12 mW and a repetition rate of 79.46 kHz, corresponding to the maximum single-pulse energy of 165.11 nJ and the shortest single-pulse width of 1.55 μs. In addition, we obtain narrower pulsewidth by dropping the black phosphorus solution onto the tapered fiber. The maximum single pulse energy of 114.72 nJ and the minimum pulsewidth of 1.09 μs were obtained. The repetition rate ranges from 49.13 to 101.3 kHz.

A high-energy passively Q-switched Yb-doped fiber laser based on WS2 and Bi2Te3 saturable absorbers

In this paper, we report two different saturable absorbers based on WS2 film and Bi2Te3 film with similar preparation processes. A high-energy stable Q-switching pulse is achieved in identical cavity configurations for each absorber. A modulation depth of 10.17% and a maximum single pulse energy of 56.50 nJ are obtained when employing the WS2 film. However, using the Bi2Te3 film we obtain a higher modulation depth of 23.04% and a larger single pulse energy of 61.80 nJ, and stable dual-wavelength Q-switching operation was shown at a pump power of 92 mW.

Passively Q-switched vectorial fiber laser modulated by hybrid organic−inorganic perovskites

We report a passively Q-switched Yb-doped vectorial fiber laser based on hybrid organic-inorganic perovskites (HOIPs) CH3NH3PbI3. The nonlinear absorption properties of CH3NH3PbI3 have been investigated based on the open-aperture Z-scan technique. With the HOIPs pulse modulator, the passively Q-switched cylindrical vector beam can be generated with the shortest pulse width 919 ns, pulse repetition frequency 36.4 kHz, and pulse energy 0.77 μJ, respectively. Furthermore, the radial and azimuthal polarization pulse beam can be obtained and switched by controlling the intra-cavity polarization.

Passively Q-Switched Yb-Doped Fiber Laser Operating at 1.06 μm with Two-Dimensional Silver Nanoplate as Saturable Absorber**Supported by the Foundation of Shandong Province under Grant No J13LN28, and the National Natural Science Foundation of China under Grant No 11304184.

A two-dimensional silver nanoplate is prepared with the seed-mediated growth method and is used for achieving pulse fiber laser operation. By controlling the dimension parameters of the silver nanoplate, the surface plasmon resonance absorption peak of the material is successfully adjusted to 1068 nm. Based on the silver nanoplate as a saturable absorber, a passively Q-switched Yb-doped fiber laser operating at 1062 nm is demonstrated. The maximum average output power of 3.49 mW is obtained with a minimum pulse width of 1.84 μs at a pulse repetition rate of 65.7 kHz, and the corresponding pulse energy and peak power are 53.1 nJ and 28.8 mW, respectively.

Gold nanobipyramids as a saturable absorber for passively Q-switched Yb-doped fiber laser operation at 1.06 µm

In this letter, gold nanobipyramids (Au-NBPs) are prepared using a seed-mediated growth method. The longitudinal surface plasmon resonance (SPR) absorption peak of the Au-NBPs is located at 1068 nm by controlling the aspect of the materials. To verify the absorption properties of the Au-NBP saturable absorber (SA), a passively Q-switched Yb-doped fiber laser is demonstrated. The maximum average output power of 3.33 mW is obtained under a pumped power of 340 mW. The minimum pulse width is 2.6 µs at a pulse repetition rate of 66.3 kHz. The results prove that Au-NBP are a promising SA with the potential for important applications in the field of pulse lasers.

980-nm Q-switched photonic crystal fiber laser by MoS2 saturable absorber

We demonstrate a 980-nm Q-switch Yb-doped photonic crystal fiber laser by a multilayer molybdenum sulfide polymer composite as the broadband saturable absorber which is prepared by the chemical vapor deposition method. We achieve passively Q-switching operations at 978 nm with the pulse width of 2.7 and 0.63 μs, corresponding to the repetition rate of 212 and 221 kHz, respectively. The maximum output power is 127 mW. It is the first time that MoS2 Q-switched Yb-doped photonic crystal fiber laser at 980 nm is demonstrated. The experimental results show that few-layer MoS2 is a promising broadband saturable absorber material.

Generation of more than 40 W of average output power from a passively Q-switched Yb-doped fiber laser.

We report on the generation of 41.6 W of average output power from a passively Q-switched ytterbium-doped fiber laser using Cr4+:YAG crystal as a saturable absorber (SA). This is the highest average power from passively Q-switched fiber lasers reported so far in the literature, to our knowledge, and it has been achieved by using a specially designed T-type double-end pumping configuration. Variation in average output power, pulse energy, pulse duration, pulse frequency, and pulse-to-pulse stability has also been studied using SAs of different linear transmissions. The effect of an intracavity SA on self-pulsing dynamics was also investigated and it was observed that, at lower input pump power near threshold, the presence of an SA enhances the peak power of relaxation oscillations to trigger the generation of stimulated Raman scattering in the gain fiber. With an increase in pump power, when the passive Q-switching threshold is reached, high peak power random self-pulses regenerate into low amplitude regular Q-switched pulses. The effect of the length of the gain medium on dual-wavelength generation at very low input pump power and broadband generation at sufficiently higher pump power has also been explored.

Q-switched laser in an SMS cavity for inhibiting nonlinear effects.

In the design of high-power Q-switched fiber lasers, nonlinear effects often become barriers that prevent the scale up of pulse energy and peak power. New designs and components that could inhibit or suppress nonlinear effects are in high demand, particularly in all-fiber configurations. In this paper, we demonstrated a Q-switched Yb-doped fiber laser in a single-mode multimode single-mode (SMS) structure to inhibit fiber nonlinear effects. The laser-generated Q-switched pulses with a peak power close to 1 kW (pulse width and energy of 100 ns and 92 μJ, respectively). The output spectrum of this laser was compared with that of a Q-switched Yb-doped fiber laser built in a conventional configuration with similar output peak power. The results showed, for the first time to our knowledge, that the SMS Q-switched laser completely inhibited the stimulated Raman scattering and significantly reduced self-phase modulation.

Azimuthally polarized, passively Q-switched Yb-doped fiber laser

An azimuthally polarized and passively Q-switched ytterbium-doped fiber laser was demonstrated. With the involvement of a single lens inside the laser resonator, a birefringent crystal was used as the polarization discriminator, and a Cr4+:YAG crystal acted as the saturable absorber and also the output coupler. For the simplicity and low optical loss of the resonator cavity, this fiber laser emitted azimuthally polarized pulse with a high slope efficiency of 72.6% and high average power of 4.11W. The laser pulse had 132-ns duration and 112-kHz repetition rate at the absorbed pump power of 6.40W.

Gold nanorod as saturable absorber for Q-switched Yb-doped fiber laser

We reported on the generation of Q-switched pulse in an Yb-doped fiber laser by using a filmy polyvinyl alcohol (PVA)-based gold nanorods (GNRs) saturable absorber (SA). The GNRs are synthesized through seed-mediated method whose longitudinal surface plasmon resonance (SPR) absorption peak is located at 1038nm. The modulation depth of the GNRs SA is ∼4.06%. By gradually increasing the pump power from 62mW to 128mW, the repetition rate of Q-switched pulse increases from 8.78kHz to 20.78kHz and the pulse duration decreases from 9.43μs to 3.65μs. In addition, the dual-wavelength switchable Q-switched operation was also observed. The obtained results further expand the applications of GNRs SA to the field of Q-switched pulsed fiber lasers at 1.0μm waveband.

High-Peak Power, All-Fiber Passively Q-Switched Laser Using a Sm-Doped Fiber Saturable Absorber

An all-fiber passively Q-switched Yb-doped fiber laser with fiber saturable absorber (SA) based on a piece of Sm-doped fiber is presented. For the first time, we observe the fast stimulated Brillouin scattering Q-switched process in an Yb/Sm all-fiber laser and obtain 41 ns pulses and 1.7 kW maximum peak power. Compared with the reported traditional SA Q-switched process, the pulse energy and peak power are both improved an order of magnitude. Furthermore, a traditional SA Q-switched process with 450 ns pulsewidth and 7.5 W peak power is also obtained in the same structure by increasing the feedback of cavity's output end.