In this paper, we report 4 different saturable absorbers based on 4 transition metal dichalcogenides (MoS2, MoSe2, WS2, WSe2) and utilize them to Q-switch a ring-cavity fiber laser with identical cavity configuration. It is found that MoSe2 exhibits highest modulation depth with similar preparation process among four saturable absorbers. Q-switching operation performance is compared from the aspects of RF spectrum, optical spectrum, repetition rate and pulse duration. WS2 Q-switched fiber laser generates the most stable pulse trains compared to other 3 fiber lasers. These results demonstrate the feasibility of TMDs to Q-switch fiber laser effectively and provide a meaningful reference for further research in nonlinear fiber optics with these TMDs materials.

Q-switched fiber laser based on transition metal dichalcogenides MoS 2 , MoSe 2 , WS 2 , and WSe 2

A diode-pumped, actively Q-switched 2.8 μm fiber laser oscillator with an average output power of more than 12 W has been realized through the use of a 35 μm core erbium-doped ZBLAN fiber and an acousto-optic modulator; to our knowledge, this is the first 3 μm pulsed fiber laser in the 10 W class. Pulse energy up to 100 μJ and pulse duration down to 90 ns, corresponding to a peak power of 0.9 kW, were achieved at a repetition rate of 120 kHz.

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12 WQ-switched Er:ZBLAN fiber laser at 28 μm

We demonstrated a Q-switched fiber laser based on Tungsten Disulfide (WS2) saturable absorber. The WS2 nano-sheets were prepared by liquid phase exfoliation method and the saturable absorber was fabricated by spin-coating of few-layer WS2 nano-sheets on a side-polished fiber for pulsed operation of a fiber laser. By inserting the absorber into an Erbium-doped fiber laser cavity pumped by a 980 nm laser diode, a stable Q-switched laser operation was achieved with a tunable repetition rates from 82 kHz to 134 kHz depending on the applied pump power. The properties of the deposited WS2 film was examined using scanning electron microscopic (SEM) and atomic force microscope (AFM). Detailed optical properties of the laser output are also discussed.

All-fiber Er-doped Q-Switched laser based on Tungsten Disulfide saturable absorber

Efficient diode-pumped passively Q-switched Er:Lu2O3 laser operation at 2.84 μm was realized. A few-layer MoS2 nanosheet film on a YAG substrate, was fabricated and employed as saturable absorber (SA) in a short plane-plane cavity. Under an absorbed diode laser pump power of 7.61 W, an average output power of 1.03 W was generated with a pulse duration of 335 ns and a repetition rate of 121 kHz, resulting in a pulse energy of 8.5 μJ.

Watt-level passively Q-switched Er:Lu₂O₃ laser at 2.84 μm using MoS₂.

3 μm Ho3+-doped ZBLAN fiber lasers passively Q-switched by a Fe2+:ZnSe crystal and graphene saturable absorbers were investigated, respectively. 800 ns pulses at 2.93 µm with an energy of 460 nJ and repetition rate of 105 KHz were obtained when a Fe2+:ZnSe crystal was inserted into a free space collimating and focusing setup. A more compact and reliable Q-switched fiber laser was achieved when a graphene coated fiber mirror was butt-coupled to the angle-cleaved end of the gain fiber. 1.2 μs pulses with an energy of 1 μJ and repetition rate of 100 KHz were achieved. More than 100 mW average output power was obtained at the maximum available pump power. Our experiments demonstrate that both Fe2+:ZnSe crystal and graphene are promising saturable absorbers for pulse generation in the 3 µm wavelength region.

Fe 2+ :ZnSe and graphene Q-switched singly Ho 3+ -doped ZBLAN fiber lasers at 3 μm

The 2.94 μm Er:YAG laser Q-switched mechanically by a rotating mirror was developed. The laser generated pulses of 30 mJ energy and duration below 290 ns, which corresponds to over 100 kW peak power. It operated at the repetition rate of up to 25 Hz. To our knowledge it is the most powerful erbium laser operating at so high repetition rate. The developed laser can be successfully applied in medicine – e.g. in microsurgery of soft biological tissues.

https://iopscience.iop.org/article/10.1002/lapl.201010019/pdf

Mid-infrared Q-switched Er:YAG laser for medical applications

The high peak power hybrid Er:YAG laser, resonantly pumped at the wavelength of 1532 nm was developed. The fused silica acousto-optic modulator driven by 10 W of RF power was deployed as the Q-switch for such a laser. For the best case of Q-switching regime the pulses of 110 kW peak power (4 mJ, 37 ns) were reached at the pump power of 7.8 W and the repetition rate of 500 Hz.

Resonantly pumped, high peak power Er:YAG laser

The efficient Q-switched Ho:YAG hybrid laser resonantly pumped by a Tm:fiber (15 W CW @ 1908 nm) was developed. The performance of the laser was investigated for the operation both in free running and a Q-switching regime. The output power of 3.5 W continuous-wave (CW) for 10.2 W of incident pump power was reached at a wavelength of 2090.1 nm. In the Q-switching regime an acousto-optic modulator was applied. In the CW pumping regime the repetition rate was changed from 20 to 5000 Hz. For the best results, for a 20 Hz repetition rate, pulses of 2.5 mJ energy and 125 kW peak power were achieved. In this regime the shortest pulse of 19.07 ns FWHM was recorded. For the best case of Q-switching in a quasi-CW pumping regime (repetition rate of 20 Hz and a pulse width of 8 ms) the pulses of 127 kW peak power (2.8 mJ, 22 ns) were obtained.

Resonantly pumped acousto-optically Q-switched hybrid Ho:YAG laser

An actively Q-switched Er 3C :YAG laser operating at the wavelength of 1645 nm was developed. The system was TIR (total internal reflection), resonantly diode-pumped at the wavelength of 1532 nm with a repetition rate of 100 Hz. For 305 mJ of incident pump pulse energy, output pulse energy of 24 mJ was generated with almost 8% of optical-to-optical efficiency. At maximum pumping power the M 2 parameter of the generated beam was 1. (Some figures may appear in colour only in the online journal)

increased average output power and diffraction limited beam quality

The 2940 nm Er:YAG laser Q-switched mechanically by means of a rotating mirror was developed. It generated the output pulses of up to 30 mJ energy, below 300 ns duration and record repetition rate of 25 Hz. The developed laser was effectively used for the investigation of laser beam interaction with selected organic matter simulants.

Lukasz Galecki

Papers

Mid-infrared Q-switched Er:YAG laser for medical applications

Resonantly pumped, high peak power Er:YAG laser

Resonantly pumped acousto-optically Q-switched hybrid Ho:YAG laser

increased average output power and diffraction limited beam quality

30 mJ, TEM00, high repetition rate, mechanically Q-switched Er:YAG laser operating at 2940 nm