A kW Continuous-Wave Ytterbium-Doped All-Fiber Laser Oscillator with Domestic Fiber Components and Gain Fiber

We demonstrate a kW continuous-wave ytterbium-doped all-fiber laser oscillator with M1 domestic fiber compo- nents： a 7× I fused fiber bundle combiner, a fiber Bragg grating and a double-clad gain fiber. The oscillator operates at 1079.48nrn with 80.94% slope efficiency and shows no limit of temperature and nonlinear effects. These indicate that the passive fiber components and the gain fiber are all qualified for the high power environ- ment. No evidence of the signal power roll-over shows that this oscillator possesses the capacity to higher output with available pump power.

All-fiber linearly polarized laser oscillator by fiber coiling loss control

In this paper,we demonstrate an all-fiber linearly polarized fiber laser oscillator.The single polarization of the oscillator is achieved through the careful designing of the active fiber coiling.The relationship between fiber coiling diameter and polarization extinction ratio and optical efficiency is studied,whose results lead to an optimized system.The thermal management of the oscillator is also refined,which allows the oscillator to reach a maximum output power of44.1 W with an optical-to-optical efficiency of 57.9%.A high average polarization extinction ratio of 21.6 d B is achieved during a 2-hour stability test.The oscillator also owns a narrow 3-d B bandwidth of 0.1 nm,as well as near-diffraction-limit beam quality of M^2～ 1.14.

Fabrication of Tm-Doped Fibers for High Power and 121W Output All-Fiber Tm-Doped Fiber Laser

We fabricate the Tm-doped double cladding silica fiber by using the vapor-solution hybrid-doping method, then build up an all-fiber Tin-doped fiber laser which can provide the output power of up to 121 W, corresponding to a slope efficiency of 51% and an optical-optical efficiency of 48%. By using the domestic Tin-doped fiber, it is the first time a hundred-watt level output at 1915nm has been achieved, to the best of our knowledge. The thermal effect of Tm-doped fiber laser is also analyzed.

Q-Switched Ytterbium-Doped Fiber Laser Using Black Phosphorus as Saturable Absorber

We demonstrate a Q-switched ytterbium-doped fiber laser （YDFL） using a newly developed multi-layer black phosphorous （BP） saturable absorber （SA）. The BP SA is prepared by mechanically exfoliating a BP crystal and sticking the acquired BP flakes onto a scotch tape. A small piece of the tape is then placed between two ferrules and incorporated in a YDFL cavity to achieve a stable Q-switched operation in a 1.0 μm region. The laser has a pump threshold of 55.1 mW, a pulse repetition rate that is tunable from 8.2 to 32.9 kHz, and the narrowest pulse width of 10.8 μs. The highest pulse energy of 328 nJ is achieved at the pump power of 97.6 mW. Our results show that multi-layer BP is a promising SA for Q-switching laser operation.

Wavelength-Tunable Single Frequency Ytterbium-Doped Fiber Laser with Loop Mirror Filter

By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.

Erbium-Doped Zirconia-Alumina Silica Glass-Based Fiber as a Saturable Absorber for High Repetition Rate Q-Switched All-Fiber Laser Generation

We propose and demonstrate a Q-switched erbium-doped fiber laser （EDFL） using an erbium-doped zirconia-alumina silica glass-based fiber （Zr-EDF） as a saturable absorber. As a 16-cm-long Zr-EDF is incorporated into a ring EDFL cavity, a stable Q-switching pulse train operating at 1565？nm wavelength is successfully obtained. The repetition rate is tunable from 33.97？kHz to 71.23？kHz by increasing the pump power from the threshold of 26？mW to the maximum of 74？mW. The highest pulse energy of 26.67？nJ is obtained at the maximum pump power.

An Efficient Single-Frequency Yb-Doped All-Fiber MOPA Laser at 1064.3 nm

An efficient narrow=linewidth single-frequency （SF） Yb-doped all-fiber master oscillator power amplifier （MOPA） laser operating at 1064.3 nm is demonstrated experimentally. A ring cavity SF fiber laser is used as the seed source for the MOPA system and the Yb-doped fibers are employed as the gain medium or the saturable absorber. The SF operation is observed to be stable without mode hopping. The highest output power of 266 mW is obtained under the 400row pump power with the corresponding slope efficiency of 66.2-. The Hnewidth of the amplified output laser is approximately I kHz and its optical signal-to-noise ratio is over 45 dB.

Sequential generation of self-starting diverse operations in all-fiber laser based on thulium-doped fiber saturable absorber

Self-starting Q-switching,Q-switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time.The central wavelengths of Q-switching,Q-switched mode-locking and mode-locking operation modes are 1569.7 nm,1570.9 nm,and 1572 nm,respectively.The mode-locking operation of the proposed fiber laser generates stable dark soliton with a repetition rate of 0.99 MHz and signal-to-noise ratio of 65 dB.The results validate the capability of generating soliton pulse by doped fiber saturable absorber.Furthermore,the proposed fiber laser is beneficial to the applications of optical communication and signal processing system.

Wavelength-Tunable Rectangular Pulses Generated from All-Fiber Mode-Locked Laser Based on Semiconductor Saturable Absorber Mirror

The wavelength-tunable rectangular mode-locking operation is demonstrated in an all-fiber laser based on semi- conductor saturable absorber mirror. As the dissipative soliton resonance signature, the pulse duration varies from 5SOps to 2.1 ns as a function o~ the increasing pump power. Correspondingly, the maximum pulse energy is 9.11 n3. Moreover, it is found that the wavelength tunable operation with a range of approximately 10 nm could be obtained by properly adjusting the polarization controllers. The characteristics of the rectangular pulses at different wavelengths are similar to each other. The demonstration of the wavelength tunable rectangular pulses would be beneficial to some applications for many fields such as spectroscopy and sensing research.

Dual-Wavelength Passively Q-Switched Ytterbium-Doped Fiber Laser Based on Aluminum Oxide Nanoparticle Saturable Absorbers

We report on generation of a dual-wavelength, all-fiber, passively Q-switched ytterbium-doped fiber laser using aluminum oxide nanoparticle （Al2O3-NP） thin film. A thin film of Al2O3 was prepared by embedding Al2O3-NPs into a polyvinyl alcohol （PVA） as a host polymer, and then inserted between two fiber ferrules to act as a saturable absorber （SA）. By incorporating the Al2O3-PVA SA into the laser cavity, a stable dual-wavelength pulse output centered at 1050 and 1060.7nm is observed at threshold pump power of 80mW. As the pump power is gradually increased from 80 to 300mW, the repetition rate of the generated pulse increases from 16.23 to 59 kHz, while the pulse width decreases from 19 to 6μs. To the best of our knowledge, this is the first demonstration for this type of SA operating in the 1 μm region.

Optical properties of ytterbium-doped tandem-pumped fiber oscillator

With the rapid development of ytterbium-doped fiber lasers, some obtrusive limitations on power scaling appeared. In order to avoid these problems, a scheme called tandem pumping is introduced into the fiber laser field. In this paper, the optical properties of an ytterbium-doped tandem-pumped fiber oscillator are presented. According to the oscillator profile, the proper gain fiber type and pump wavelength range are picked out, under the comprehensive consideration of laser conversion efficiency and beam quality. In addition, the photodarkening performances of tandem pumping lasers and conventional ones are compared based on practical application, with all possible impact parameters taken into account. Moreover, an all-fibered tandem-pumped oscillator centered at 1079.5 nm is built, in the way of clad pumping by a 1030-nm fiber laser. The laser power of the oscillator reaches 7 W, with an opto-optic efficiency of 82.4%.

Q-switched giant pulsed erbium-doped all-fiber laser with V_(2)ZnC MAX phase saturable absorber

MXenes,drawn from MAX phases,are special two-dimensional substances with numerous advantages in nonlinear optics,specifically in giant and ultrashort pulsed-laser applications.Ti_(3)C_(2)T_(x)and Ti_(2)CT_(x)nanosheets however rapidly deteriorate under ambient conditions,limiting their applications.This paper demonstrates how excellent modulation depth of one of the MAX phase compounds vanadium zinc carbide(V_2ZnC)makes it a brilliant saturable absorber(SA)in passively Q-switched all-fiber pulsed lasers,integrated such that a 16.73-μm V_(2)ZnC-polyvinyl alcohol(PVA)thin film acts as SA in the laser.Saturable and non-saturable absorptions were found to be 13.2%and 10.47%,while saturation optical intensity and modulation depth were 6.25 k W/cm^(2)and 12.43%,respectively,illustrating the optical nonlinearity.The superiority of MAX-PVA,fabricated in four distinct ratios,was demonstrated by the fact that it self-starts a giant pulsed laser at pump power as low as 22.5 mW and firmly accomplished 120.6 kHz repetition rate with a pulse width of 2.08μs.It is a fine SA for the use of pulsed-laser production using all-fiber laser due to fabrication simplicity and great optical,thermophysical,and mechanical qualities.

2.8 μm all-fiber Q-switched and mode-locked lasers with black phosphorus

In past years, rare-earth-doped fluoride fiber lasers(FFLs) have developed rapidly in the mid-infrared(mid-IR)region. However, due to the lack of fiber optic devices and challenge of fluoride fiber splicing, most mid-IR FFLs have been demonstrated with free-space optic elements, limiting the advantages of all-fiber lasers for flexible delivery, stability, and compactness. Here, we report, to the best of our knowledge, the first pulsed all-fiber FFL in the mid-IR region. By taking advantage of the integration of black phosphorus flake, stable Q-switched and mode-locked pulses were obtained at 2.8 μm wavelength. We believe that this all-fiber design will promote the application of pulsed FFL in the mid-IR region.

Investigation on Material Response of 55% SiCp/Al Composites Induced by Pulsed Laser

Silicon carbide particle reinforced aluminum matrix composites(SiCp/Al composites)are widely used in aviation,aerospace and electronic package.However,low machining efficiency,severe tool wear and poor surface quality are severe during the machining of SiCp/Al composites.Laser-induced oxidation is capable to improve the machinability of SiCp/Al composites.The material response of 55%(volume fraction)SiCp/Al composites induced by a nanosecond pulsed laser is studied.A metamorphic layer which is composed of an oxide layer and sub-layer is produced.The effects of reaction surrounding and laser average power on the microstructure and thickness of the oxide layer and sub-layer are investigated.Experimental results show that:A thicker oxide layer and a sub-layer are formed in an oxygen-rich atmosphere.The oxides are mainly composed of 2Al2O3·SiO2(mullite).A positive correlation between the laser average power and thicknesses of oxide layers and sub-layers is found.A loose oxide layer of 138μm and a sub-layer of 21μm are formed at the laser average power of 6 W,laser scanning pitch of 10μm,and laser scanning speed of 1 mm/s under an oxygen-rich atmosphere.The high efficient machining of Si Cp/Al composites can be realized by laser-induced oxidation.

Ternary ReS_(2(1-x))Se_(2x) alloy saturable absorber for passively Q-switched and mode-locked erbium-doped all-fiber lasers

We report Q-switched and mode-locked erbium-doped all-fiber lasers using ternary ReS_(2(1-x))Se_(2x) as saturable absorbers(SAs). The modulation depth and saturable intensity of the film SA are 1.8% and 0.046 MW∕cm2.In Q-switched mechanism output, the pulse was centered at 1531.1 nm with maximum pulse energy and minimum pulse width of 28.29 nJ and 1.07 μs, respectively. In mode-locked operation, the pulse was centered at1561.15 nm with pulse width of 888 fs, repetition rate of 2.95 MHz, and maximum pulse energy of 0.275 nJ. To the best of our knowledge, this is the first report on the mode-locked Er^(3+)-doped fiber laser using ternary transition metal dichalcogenides. This work suggests prospective 2 D-material SAs can be widely used in versatile fields due to their attractive optoelectronic and tunable energy bandgap properties.

High-energy pulse generation using Yb-doped Q-switched fiber laser based on single-walled carbon nanotubes

An all-fiber laser using a single-walled carbon nanotube（SWCNT） as the saturable absorber（SA） for Q-switched operation in the 1031 nm region is demonstrated in this work. A lasing threshold as low as 17 mW was realized for continuous wave operation. By further increasing the pump power, stable Q-switched pulse trains are obtained when the pump power ranges from 38 mW to 125 mW, corresponding to repetition rate varying from 40.84 kHz to 66.24 kHz, the pulse width from 2.0 μs to 1.0 μs,and the highest single pulse energy of 40.6 nJ respectively.

Er^(3+)-Yb^(3+) Co-Doped Fiber Ring and Line Laser

Er3+-Yb3+ co-doped fiber of 2 m long is used as the laser gain medium. Two fiber lasers with different structures have been set up, one is the line cavity fiber laser with the dielectric mirror being replaced by an all-fiber reflecting mirror,the other is the ring cavity all-fiber laser. Both set-ups have achieved lasing operation at the wavelength of 1.53 μm. Pumped by the 1 064 nm light from all-solid-state Nd ∶YAG laser, the two fiber lasers at 1 530 nm are operational. Their output powers are 7.8 mW and 2 mW with 130 mW and 160 mW pump powers.

Towards all-fiber structure pulsed mid-infrared laser by gas-filled hollow-core fibers

We report here on a diode-pumped pulsed mid-infrared laser source based on gas-filled hollow-core fibers(HCFs)towards an all-fiber structure by the tapering method. The pump laser is coupled into an acetylene-filled HCF through a tapered single-mode fiber. By precisely tuning the wavelength of the diode to match different absorption lines of acetylene near 1.5 μm, mid-infrared emission around 3.1–3.2 μm is generated. With 2 m HCFs and3 mbar acetylene gas, a maximum average power of 130 m W is obtained with a laser slope efficiency of ~24%.This work provides a potential scheme for all-fiber mid-infrared fiber gas lasers.

Nanosecond-pulsed, dual-wavelength, passively Q-switched ytterbium-doped bulk laser based on few-layer MoS2 saturable absorber

A compact saturable absorber mirror（SAM） based on few-layer molybdenum disulfide（MoS2） nanoplatelets was fabricated and successfully used as an efficient saturable absorber（SA） for the passively Q-switched solid-state laser at 1 μm wavelength. Pulses as short as 182 ns were obtained from a ytterbium-doped（Yb:LGGG） bulk laser Q-switched by the MoS2 SAM, which we believe to be the shortest one ever achieved from the MoS2 SAs-based Q-switched bulk lasers. A maximum average output power of 0.6 W was obtained with a slope efficiency of 24%,corresponding to single pulse energy up to 1.8 μJ. In addition, the simultaneous dual-wavelength Q-switching at 1025.2 and 1028.1 nm has been successfully achieved. The results indicate the promising potential of few-layer MoS2 nanoplatelets as nonlinear optical switches for achieving efficient pulsed bulk lasers.

2×3 kW bidirectional output fiber oscillator employing spindle-shaped ytterbium-doped fiber

A 2×3 kW-level bidirectional output fiber oscillator is realized by combining the specially designed spindle-shaped ytterbium-doped fiber,non-wavelength-stabilized 976-nm LDs,and grating bandwidth optimization to balance transverse mode instability and stimulated Raman scattering.The maximum output powers at both ends are 3265 and 2840 W,respectively,with a total efficiency of 73.2%.The M^(2) factors of the lasers at both ends are about 1.98 and 2.38,respectively.The beam profile at both ends shows that a bidirectional output annular beam fiber oscillator has been realized,which has great potential in practical applications.