High-power diode-end-pumped Tm：YAP and Tm：YLF slab lasers

Diode-end-pumped continuous-wave(CW) Tm:YAP and Tm:YLF slab lasers are demonstrated. The a-cut Tm:YAP and Tm:YLF slabs with doping concentrations of 4 at.-% and 3.5 at.-%,respectively,are pumped by fast-axis collimated laser diodes at room temperature. The maximum CW output powers of 72 and 50.2 W are obtained from Tm:YAP and Tm:YLF,respectively,while the pump power is 220 W,corresponding to the slope efficiencies of 37.9% and 26.6%,respectively.     

Tunable CW Tm,Ho:YLF laser at 2

A tunable continuous wave (CW) low temperature operating Tm (6 at.-%),Ho (0.6 at.-%):YLF laser pumped by fiber-coupled diode laser is reported. The maximum output power is 4.16 W at 2073 nm by use of 30% output coupling, the slope efficiency is 33%. A tuning range from 2049 to 2081 nm is achieved with a birefringent filter (BF). The factors that contribute to the output power and tuning range are discussed.     

Tunable CW Tm,Ho:YLF laser at 2μm

A tunable continuous wave (CW) low temperature operating Tm (6 at.-%),Ho (0.6 at.-%):YLF laser pumped by fiber-coupled diode laser is reported. The maximum output power is 4.16 W at 2073 nm by use of 30% output coupling, the slope efficiency is 33%. A tuning range from 2049 to 2081 nm is achieved with a birefringent filter (BF). The factors that contribute to the output power and tuning range are discussed.     

Performance evaluation of ZnGeP_2 optical parametric oscillator pumped by a Q-switched Tm,Ho:GdVO_4 laser

A doubly resonant ZnGeP_2(ZGP)optical parametric oscillator(OPO)pumped by a novel Tm.Ho:GdVO_4 laser was demonstrated.Cryogenic Tm(5 at.-%),Ho(0.5 at.-%):GdVO_4 laser with high pulse repetition frequency(PRF)of 10 kHz at 2.05μm was employed as pumping source of ZGP OPO.The 15-mm-long ZGP crystal,55°cut forⅠ-type phase-matching with low absorption coefficient less than 0.05 cm~(-1)at 2 #m, was placed in a plano-plano cavity with resonator length of 30 mm.The ZGP OPO generated a total combined output power of 1.2 W at 3.75 and 4.52μm under pumping power of 5.3 W,corresponding to slope efficiency of 40% from incident 2-μm laser power to mid-infrared(Mid-IR)output.A widely tunable range from 3.0 to 6.5μm was achieved by changing the crystal angle only 3.5°.     

A Stable Diffusion-Bonded Tm：YLF Bulk Laser with High Power Output at a Wavelength of 1889.5 nm

A high power diode-pumped diffusion-bonded Tm：YLF laser operating at 1889.5nm with a FWHM linewidth of less than 0.1 nm is reported. A Brewster plate and two Fabry-Perot etalons are inserted in the laser cavity for spectral narrowing and stabilization. Under an incident pump power of 136.8 W, 46.1 W of output power is achieved, corresponding to an optical-to-optical conversion efficiency of 33.7% and a slope efficiency of 42.8%. The laser wavelength shift of only 0.07nm with the incident pump power from 20.1 W to 136.8W is observed. The M2 factor at maximum output power is calculated to be 2.3 in the x-axis and 2.0 in the y-axis, respectively.     

589-nm yellow laser generation by intra-cavity sum-frequency mixing in a T-shaped Nd:YAG laser cavity

To obtain high power 589-nm yellow laser, a T-shaped thermal-insensitive cavity is designed. The optimal power ratio of 1064- and 1319-nm beams is considered and the fundamental spot size distribution from the output mirror to the two laser rods are calculated and simulated, respectively. As a result, a 589-nm yellow laser with the average output power of 5.7 W is obtained in the experiment when the total pumping power is 695 W. The optical-to-optical conversion efficiency from the fundamental waves to the sum frequency generation is about 15.2% and the pulse width is 150 ns at the repetition rate of 18 kHz. The instability of the yellow laser is also measured, which is less than 2% within 3 h. The beam quality factors are Mx^2 = 4.96 and My^2 = 5.08.     

High-power near diffraction-limited 1 064-nm Nd:YAG rod laser and second harmonic generation by intracavity-frequency-doubling

We present a near diffraction-limited 1 064-nm Nd:YAG rod laser with output power of 82.3 W(M~2≈1.38). The power fluctuation over two hours is better than±1.1%.Pulsed 1064-nm laser with an average power of 66.6 W and pulse width of 46 ns are achieved when the laser is Q-switched at a repetition rate of 10 kHz.The short pulse duration stems from the short cavity as well as the high-gain laser modules. Using intracavity-frequency-doubling,a 35.0-W near diffraction-limited 532-nm green laser(M~2≈1.32) is achieved with a pulse width of 43 ns.     

A Compact High Power Laser-Diode Side-Pumped Tm,Ho：YAG Laser Nearly at Room Temperature with Intracavity Tm：YAG Laser

We report a compact high power Tm,Ho：YAG laser nearly at room temperature. The laser-diode side-pumped Tm：YAG and Tm,Ho：YAG laser modules are operated in the same cavity. The laser yields 37.34 W of continuous wave output power under the temperature of 6℃, corresponding to a maximum slope efficiency of 16.7% when the output power lies from 5.1 W to 27.0 W. This is the first report on the combined Tm：YAG and Tm,Ho：YAG lasers for obtaining high power 2.1 μm laser.     

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.     

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.     

Experimental study of continuous-wave and Q-switched laser performances of Ho:YVO4 crystal

In this letter, we report a Ho:YVO4 laser pumped by a 1.94-μm laser in both continuous-wave(CW)and Q-switched modes. The output performance of the Ho:YVO4 laser is compared with different output coupler transmissions. By use of the output coupler transmissions of T =30%, we obtain the maximum CW output power of 3.9 W at 2052 nm, with beam quality factor of M2=1.09 for the absorbed pump power of 12.5 W. For the Q-switched mode, we achieve maximum output energy per pulse of 0.38 mJ and the minimum pulse width of 25 ns, corresponding to the peak power of 15.2 kW.     

Nonlinear Polarization Rotation-Based Mode-Locked Erbium-Doped Fiber Laser with Three Switchable Operation States

A simple mode-locked erbium-doped fiber laser （EDFL） with three switchable operation states is proposed and demonstrated based on nonlinear polarization rotation. The EDFL generates a stable square pulse at a third harmonic pulse repetition rate of 87kHz as the 1480 nm pump power increases from the threshold of 17.5 m W to 34.3mW. The square pulse duration increases from 105 ns to 245ns as the pump power increases within this region. The pulse operation switches to the second operation state as the pump power is varied from 48.2mW to l16.Tm W. The laser operates at a fundamental repetition rate of 29 kHz with a fixed pulse width of 8.5 μs within the pump power region. At a pump power of ll6.TmW, the average output power is 3.84mW, which corresponds to the pulse energy of 131.5 ng. When the pump power continues to increase, the pulse train experiences unstable oscillation before it reaches the third stable operation state within a pump power region of 138.9 m W to 145.0 m W. Within this region, the EDFL produces a fixed pulse width of 2.8 μs and a harmonic pulse repetition rate of 58 kHz.     

High-power passively Q-switched Nd:GdVO_4 laser with a reflective graphene oxide saturable absorber

A single output Q-switched Nd:GdVO4 laser with a reflective graphene oxide(GO) saturable absorber was demonstrated. The shortest pulse duration in the Q-switched laser is 115 ns, and the output power ranges from1.23 W at 1.71 MHz to 2.11 W at 2.50 MHz when the pump power rises from 7.40 to 10.90 W with the utilization of GO Langmuir–Blodgett(LB) films based on the convenient and low-cost LB technique. To the best of our knowledge, it is the highest output power in a Q-switched laser with a GO saturable absorber.     

Supercontinuum generation in a standard single-mode fiber by a Q-switched Tm,Ho:YVO4 laser

Broadband mid-infrared(IR) supercontinuum laser is generated in standard single-mode fiber-28 directly pumped by a 2054 nm nanosecond Q-switched Tm,Ho:YVO4 laser. The average output powers of 0.53 W in the ~1.95–2.5 μm spectral band and 0.65 W in the ~1.97–2.45 μm spectral band are achieved at pulse rate frequencies of 7 and 10 kHz, and the corresponding optic-to-optic conversion efficiencies are 34.6% and 42.4% by considering the coupling efficiency. The output spectra have extremely high flatness in the range 2060–2400 and 2060–2360 nm with negligible intensity variation(2%), respectively. The output pulse shape is not split, and pulse width is reduced from 29 to ~15.4 ns. The beam quality factor M2 is 1.06, measured using traveling knife-edge method, and the laser beam spot is also monitored by an IR vidicon camera.     

Diode-pumped laser performance of Tm:Sc_2SiO_5 crystal at 1971 nm

The 4-at.% Tm:Sc_2SiO_5 (Tm:SSO) crystal is successfully obtained by the Czochralski method. The optical properties and thermal conductivity of the crystal are investigated. The broad continuous wave(CW) laser output of(100)-cut Tm:SSO with the dimensions of 3 mm×3 mm×3 mm under laser diode(LD)-pumping is realized. The full width at half maximum(FWHM) of the laser emitting reaches up to 21 nm. The laser threshold of Tm:SSO is measured to be 0.43 W. Efficient diode-pumped CW laser performance of Tm:SSO is demonstrated with a slope efficiency of 25.9% and maximum output power of 934 mW.     

Compact, Low Threshold Nd^3＋：YVO4 Self-Raman Laser at 1178 nm

A compact low-threshold Raman laser at 1178 nm is experimentally realized by using a diode-end-pumped actively Q-switched Nd^3＋ ：YVO4 self-Raman laser. The threshold is 370mW at a pulse repetition frequency of S kHz. The maximum Raman laser output is 182 m W with the pulse duration smaller than 20 ns at a pulse repetition frequency of 30kHz with 1.8 W incident power. The optical efficiency from the incident power to the Raman laser is 10% and the slope efficiency is 13.5%.     

Harmonically pump a femtosecond optical parametric oscillator to 1.13 GHz by a femtosecond 515 nm laser

We demonstrate a harmonically pumped femtosecond optical parametric oscillator(OPO)laser using a frequency-doubled mode-locked Yb:KGW laser at a repetition rate of 75.5 MHz as the pump laser.Based on a bismuth borate nonlinear crystal,repetition rates up to 1.13 GHz are realized,which is 15 times that of the pump laser.The signal wavelength is tunable from 700 nm to 887 nm.The maximum power of the signal is 207 m W at the central wavelength of 750 nm and the shortest pulse duration is 117 fs at 780 nm.The beam quality(M^2 factor)in the horizontal and vertical directions of the output beam are 1.077 and 1.141,respectively.     

Performance of gain-switched all-solid-state quasi-continuous-wave tunable Ti:sapphire laser system

We have made a gain-switched all-solid-state quasi-continuous-wave （QCW） tunable Ti：sapphire laser system, which is pumped by a 532 nm intracavity frequency-doubled Nd：YAG laser. Based on the theory of gain-switching and the study on the influencing factors of the output pulse width, an effective method for obtaining high power and narrow pulse width output is proposed. Through deliberately designing the pump source and the resonator of the Ti：sapphire laser, when the repetition rate is 6 kHz and the length of the cavity is 220 mm, at an incident pump power of 22 W, the tunable Ti：sapphire laser from 700 to 950nm can be achieved. It has a maximum average output power of 5.6W at 800nm and the pulse width of 13.2 ns, giving an optical conversion efficiency of 25.5% from the 532 mn pump laser to the Ti：sapphire laser.     

Diode-pumped Tm:LuAG laser at room temperature

The lasing characteristics of Tm：LuAG at room temperature are reported. The maximum output power at 2.023-μm wavelength is 4.91 W and the slope efficiency is 25.39%. The mode matching between pump mode and laser mode is optimized by changing the pump beam waist radius and its location. Different output couplers are used to realize the optimal laser output. The relationship between operation temperature and output power is also discussed.     

Widely continuous-tunable 2.789-4.957 μm twin- MgO：PPLN cascaded optical parametric oscillator

An all-solid-state mid-infrared optical parametric oscillator with wide tunability by using two identical multi-grating periodically poled 5-mol.-% MgO-doped lithium niobate cascaded is reported. The pump laser is an acousto-optically Q-switched Nd：YAG laser with 150-ns pulse width at repetition rate of 10 kHz. Wide tunability from 2.789 to 4.957μm at the idler wavelength is achieved by varying the temperature from 40 to 200 ~C and translating the grating periods from 26 to 31 μm with a step of 0.5μm. When the incident pump average power is 8.15 W, the maximum idler output average power is 2.23 W at 3.344 μm and the optic-optic conversion efficiency is about 27.4%.