Wavelength tunable passively Q-switched Yb-doped double-clad f iber laser with graphene grown on SiC

A passively Q-switched tunable Yb-doped double-clad fiber laser is demonstrated with graphene epitaxially grown on SiC.The spectral tuning of the Q-switched fiber laser is implemented by rotating a quartz plate filter inside the cavity.The central wavelength of the fiber laser can be continuously tuned from 1038.54 to 1056.22 nm.The maximum pulse energy of 0.65 μJ is obtained at the pump power of 4.08 W,and the corresponding pulse duration and average output power are 1.60 μs and 35 mW,respectively.     

A novel 2-μm pulsed fiber laser based on a supercontinuum source and its application to mid-infrared supercontinuum generation

A new method to achieve 2-μm pulsed fiber lasers based on a supercontinuum(SC) is demonstrated. The incident pump light is a pulsed SC which contains a pump light and a signal light at the same time. The initial signal of the seed laser is provided by the incident pump light and amplified in the cavity. Based on this, we obtain a 2-μm pulsed laser with pulse repetition rate of 50 kHz and pulse width of 2 ns from the Tm-doped fiber laser. This 2-μm pulsed laser is amplified by two stages of fiber amplifiers, then the amplified laser is used for mid-infrared(mid-IR) SC generation in a 10-m length of ZrF4–BaF2–LaF3–AlF3–NaF(ZBLAN) fiber. An all-fiber-integrated mid-IR SC with spectrum ranging from 1.8 μm to4.3 μm is achieved. The maximal average output power of the mid-IR SC from the ZBLAN fiber is 1.24 W(average output power beyond 2.5 μm is 340 mW), corresponding to an output efficiency of 6.6% with respect to the 790-nm pump power.     

Short Tm^3＋-doped fiber lasers with watt-level output near 2 μm

High-power operation of diode-pumped fiber lasers at wavelength near 2 μm are demonstrated with short length of heavily Tm^3＋-doped silica glass fibers. With 7-cm long fiber, a laser at near 2 μm is obtained with the threshold of 135 mW, maximum output power of 1.09 W, and slope efficiency of 9.6% with respect to the launched power from a laser diode at 790 nm. The output stability of this fiber laser is within 5%. The dependence of the performance of fiber lasers on the operation temperature and cavity configuration parameters is also investigated.     

Dark pulse emission in nonlinear polarization rotation-based multiwavelength mode-locked erbium-doped fiber laser

We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser（EDFL） with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength laser with 0.47 nm spacing at 24 m W threshold pump power, while the number of lines obtained increases with the pump power. A dark pulse emission is observed as the pump power is increased above 137 m W, with fundamental repetition rate of 29 k Hz and pulse width of 2.7 μs. It is observed that the dark pulse train can be shifted to second-, third-, and fourth-order harmonic dark pulses by carefully adjusting the polarization controller. For the fundamental dark pulse, the maximum pulse energy of 32.4 n J is obtained at pump power of 146.0 mW.     

Diode-pumped 1018-nm ytterbium-doped double-clad fiber laser

We report a 1 018-nm ytterbium-doped double-clad fiber laser pumped by 970-nm diode. A pair of fiber Bragg gratings with reflectivities of 99.9% and 9% at a center wavelength of 1 018.9 nm are employed as cavity mirrors. The ytterbium-doped double-clad fiber is a 2.6-m-long Liekki fiber. Laser output power of 7.5 W at 1 018 nm is obtained under the pump power of 59.2 W. The overall slope efficiency of the fiber laser is about 16%. This low slope efficiency is mainly due to the incomplete absorption of the pump power.     

122-W high-power single-frequency MOPA fiber laser in all-fiber format

We demonstrate a high-power single-frequency master oscillator power amplifier (MOPA) fiber laser.The central wavelength of the single-frequency fiber laser seed is 1 063.8 nm,with a linewidth narrower than 20 kHz and output power of 120 mW.By using two-stage amplification,a single-frequency fiber laser with an output power of 122 W is obtained,and the optical-optical conversion efficiency is 72%.No significant amplified spontaneous emission (ASE) or stimulated Brillouin scattering (SBS) is observed.The output power can be further increased by launching more pump power.     

Experimental and numerical investigation of mid-infrared laser in Pr~(3+)-doped chalcogenide fiber

We report on a chalcogenide glass fiber doped with Pr~(3+) that can be used for commercialized 1.5-μm and 2-μm laser excitations by emitting broadband 3 μm–5.5 μm fluorescence, which is extruded into a preform and then drawn into a step-index fiber. The spectroscopic properties of the fiber and glass are reported, and the mid-infrared fiber lasers are also numerically investigated. Cascade lasing is employed to increase the inversion population of the upper laser level. The particle swarm approach is applied to optimize the fiber laser parameters. The output power can reach 1.28 W at 4.89-μm wavelength, with a pump power of 5 W, excitation wavelength at 2.04 μm, Pr~(3+) ion concentration at 4.22 × 10~(25) ions/m~3,fiber length at 0.94 m, and fiber background loss at 3 dB/m.     

Watt-level Yb-doped silica glass fiber laser with a core made by sol-gel method

A Yb-doped silica glass fiber laser with a core made by sol-gel method is reported. The maximum power of 1.14 W is obtained with a pump power of 5.46 W at a wavelength of 976 nm. The slope efficiency is 34%. The refractive index fluctuation across the core is below 5×10^-4 at a doping level of Yb 0.15 mol%, A203 4.0 mol%, and P2O5 2.0 mol%. High background attenuation of 6 dB/m at 1 053 nm limites the slope efficiency and maximum output power.     

Generation of 131 fs mode-locked pulses from 2.8μm Er:ZBLAN fiber laser

We demonstrated a femtosecond mode-locked Er:Zr F4-Ba F2-La F3-Al F3-Na F(Er:ZBLAN)fiber laser at 2.8μm based on the nonlinear polarization rotation technique.The laser generated an average output power of 317 m W with a repetition rate of 107 MHz and pulse duration as short as 131 fs.To the best of our knowledge,this is the shortest pulse generated directly from a mid-infrared mode-locked Er:ZBLAN fiber laser to date.Numerical simulation and experimental results confirm that reducing the gain fiber length is an effective way to shorten the mode-locked pulse duration in the Er:ZBLAN fiber laser.The work takes an important step towards sub-100-fs mid-infrared pulse generation from mode-locked Er:ZBLAN fiber lasers.     

Linearly polarized operation of Yb-doped fiber laser by Brewster's angle-polished fiber end

<正>A new method to obtain linear polarization operation by Brewster's angle-polished fiber end is demonstrated. By using the special polarization operation technique together with introducing a narrow-linewidth fiber grating into the laser cavity,a cladding-pumped linear polarization and single-transverse-mode (M~21.1) Yb-doped fiber laser with narrow linewidth whose full-width at half-maximm(FWHM) is less than 0.2 nm,is obtained in a simple configuration.The output power is up to 10 W which is continuouswave output at 1085 nm,and the slope efficiency is 63%with respect to the coupled pump power and 75%with respect to the absorbed pump power,respectively.The measured 21-dB polarization extinction ratio does not degrade with the output power.The simplicity of such an approach is highly beneficial for a number of applications,including the use of a fiber laser for the nonlinear wavelength conversion (especially for the intracavity frequency doubling) and for the coherent and spectral beam combination.     

High peak power 1.0 μm and tri-wavelength 1.3 μm Nd:ScYSiO_5 crystal lasers

With a Nd:ScYSiO_5 crystal, a high peak power electro-optically Q-switched 1.0 μm laser and tri-wavelength laser operations at the 1.3 μm band are both investigated. With a rubidium titanyle phosphate(RTP) electro-optical switcher and a polarization beam splitter, a high signal-to-noise ratio 1.0 μm laser is obtained, generating a shortest pulse width of 30 ns, a highest pulse energy of 0.765 mJ, and a maximum peak power of 25.5 kW,respectively. The laser mode at the highest laser energy level is the TEM200 mode with the Mvalue in the X and Y directions to be M_x~2= 1.52 and M_y~2= 1.54. A tri-wavelength Nd:ScYSiO_5 crystal laser at 1.3 μm is also investigated. A maximum tri-wavelength output power is 1.03 W under the absorbed pump power of7 W, corresponding to a slope efficiency of 14.8%. The properties of the output wavelength are fully studied under different absorbed pump power.     

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.     

Experimental and Numerical Investigation of Single Frequency Amplifier with Photonic Bandgap Fiber at 1178 nm

A single frequency photonic bandgap fiber amplifier at 11 78nm is iuvestigated experimentally and numerically.With a pump power of 81 W, a single frequency 1178nm fiber laser of 10.3 W is obtained with a 3 W seed laser and a 20m gain fiber. Numerical simulation is conducted with a rate equation model taking amplified spontaneous emission and stimulated Brillouin scattering （SBS） into consideration. Temperature distribution along the fiber is applied for SBS suppression, more than 50 W single frequeney fiber laser at 1178 nm is predicted theoreticall.v with a 5 W seed laser and a 40m long gain fiber with five temperature steps.     

High-power double-clad large-mode-area photonic crystal fiber laser

A high power double-clad ytterbium-doped large-mode-area photonic crystal fiber (LMA PCF) laser was demonstrated using a unique Fabry-Perot (F-P) configuration. The pump source is a fiber coupled diode array operating at 976 nm. A continuous wave (CW) output power of 50 W at ～ 1.04 μm with a slope efficiency of 76.3% is obtained. Single transverse mode operation is achieved without any thermal-optical problems. This laser has the potential for scaling to much higher output power.     

Q-switched ytterbium doped carbon nanotubes fiber laser using multi-walled saturable absorber

A Q-switched ytterbium-doped fiber laser （YDFL） is proposed and demonstrated using a newly developed multi-walled carbon nanotubes polyethylene oxide （MWCNTs-PEO） film as a passive saturable absorber （SA）. The saturable absorber is prepared by mixing the MWCNTs homogeneous solution into a dilute PEO polymer solution before it is left to dry at room temperature to produce thin film. Then the film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity for Q-switching pulse generation. The laser generates a stable pulse operating at wavelength of 1060.2 nm with a threshold pump power of 53.43 mW. The YDFL generates a stable pulse train with repetition rates ranging from 7.92 to 24.27 kHz by varying 980-nm pump power from 53.42 to 65.72 mW. At 59.55-mW pump power, the lowest pulse width and the highest pulse energy are obtained at 12.18 μs and 143.5 n J, respectively.     

High Efficiency Continuous-Wave Tm：Ho：GdVO4 Laser Pumped by a Diode

We report a high efficiency cw diode-pumped cryogenic Tin(Sat.%), Ho(0.5at.%):GdV04 laser. The pumping source is a fibre-coupled laser diode with fibre core diameter of 0.4 mm and numerical aperture of 0.3, supplying power 14.8 W at 793.6nm. For input pump power of 13.6 W at 794.2nm, the maximum output power of 4.2 W,optical-to-optical conversion efficiency of 31% and slope efficiency 38% have been attained at 2.0485 μm. To our knowledge, the operating performance is the best among the previously reported Tm:Ho:GdVO4 lasers. We also analyse the influence of pump wavelengths (from 792nm to 794.2nm) on the output power, the optical-to-optical conversion efficiency increases with the longer pump wavelength which is closer to the absorption peak of 797nm in Tm,Ho:GdV04.     

Reflective graphene oxide absorber for passively mode-locked laser operating at nearly 1μm

A low cost and simply fabricated reflective graphene oxide is successfully made. By using this absorber, as well as an end reflector, we obtain a passively mode-locked Yb:LuYSiO5 laser operating at nearly 1 μm. When the pump power is increased up to 5.73 W, stable mode locking is achieved. The central wavelength of the laser spectrum is 1043.2 nm with a pulse duration of 5.0 ps. When the pump power reaches 8.16 W, dual-wavelength mode locking laser pulses at 1036.3 nm and 1043.5 nm are simultaneously detected.     

Q-Switched Large-Mode-Area Yb-Doped Fibre Laser Using GaAs as Saturable Absorber

A passive Q-switched large-mode-area Yb-doped fibre laser is demonstrated using a GaAs wafer as the saturable absorber. A high Yb doping concentration double-clad fibre with a core diameter of 30μm and a numerical aperture of 0.07 is used to increase the laser gain volume, permitting greater energy storage and higher output power than conventional fibres. The maximum average output power is 7.2W at 1080nm wavelength, with the shortest pulse duration of 580ns and the highest peak power of 161W when the laser is pumped with a 25W diode laser operating at 976nm. The repetition rate increases with the pump power linearly and the highest repetition rate of 77kHz is obtained in the experiment.     

Diode-pumped high-efficiency broadband tunable Tm:YAP laser

A laser diode-pumped high-efficiency widely tunable Tm:YAP laser with excellent comprehensive properties is reported.The output power is stable at a given pump power.Under the absorbed pump power of 12.95 W,the maximum output power at 2,010 nm is 5.16 W,corresponding to a slope efficiency of 45.5%.The generated beam profile is close to the Gaussian TEM00 near the maximum pump power.Furthermore,the laser working wavelength can be continuously tuned through optimization from 1,894 to 2,066 nm,which is the widest tunable range for Tm:YAP lasers to date.     

Efficient Diode-Pumped Tm：YALO3 Laser with a Pump Recycling Scheme

By using a pump recycling configuration, the maximum power of 8.1 W in the wavelength range 1.935-1.938 μm is generated by a 5-ram long Tm：YAIOa （4 at.%） laser operating at 18℃ with a pump power of 24 W. The highest slope efficiency of 42% is attained, and the pump quantum efficiency is up to 100%. The Tm：YAlO3 laser is employed as a pumping source of singly-doped Ho（1%）：GdV04 laser operating at room temperature, in which continuous wave output power of greater than 0.2 W at 2.05/μm is achieved with a slope efficiency of 9%.