Low-threshold continuous-wave Tm3+:YAlO3 laser

We describe a continuous-wave, low-threshold Tm:YAlO₃ (Tm:YAP) laser operating at 1945 nm with incident threshold pump powers in the 10–20 mW range. The z-cavity containing a 2-mm-long Tm:YAP crystal with 4 at.% Tm³⁺ concentration was end pumped by a continuous-wave Ti:sapphire laser at 795 nm. Tight focusing of the pump and the laser beams enabled low-threshold operation. The power performance of two different cavity configurations with 5-cm radius (R = 5 cm cavity) and 10-cm radius (R = 10 cm cavity) curved mirrors was tested. The best performance was obtained with the R = 10 cm configuration, where, the incident threshold pump power could be lowered to 10 mW after optimizing the polarization direction of the pump beam and by employing double pumping. Theoretical estimation of the threshold power was in good agreement with the experimental observations. The laser could be further tuned from 1842 to 1994 nm.     

Lasing of diode-pumped c-cut Tm, Ho:YAlO3

We report on a diode-pumped Tm, Ho:YAlO₃ (c-cut) laser operating at 274 K. The maximum output power reaches 163 mW at an absorbed pump power of 2.3 W. A conversion efficiency from the absorbed pump power to laser output of 7.1% is demonstrated in Tm, Ho:YAlO₃, corresponding to a slope efficiency of 11.1%. The output center wavelength of Tm, Ho:YAlO₃ is 2102 nm with about a 2-nm FWHM. As far as we know, our work represents the first investigation of the laser performance of c-cut Tm, Ho:YAlO₃ at 274 K.     

120-W continuous-wave diode-pumped Tm:YAG laser

We present a 120-W cw diode-pumped Tm:YAG laser. The Tm:YAG rod is side pumped by three diode arrays whose radiation is coupled through compound parabolic concentrators. The maximum optical-to-optical conversion efficiency of the 2.02-mum laser output is 25.2%, with a slope efficiency of 31.2%.     

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.     

A power-scaling strategy for longitudinally diode-pumped Tm:YLF lasers

We describe a power-scaling strategy for longitudinally diode-pumped Tm:YLF lasers based on optimisation of the thulium doping level and the gain geometry. Carefully designed laser experiments at lower powers are shown to allow a simple means for accurately predicting the thermal loading and hence the power-scaling properties of this system, including the effects of ground-state depletion, cross relaxation and energy-transfer upconversion. An optimised doping level of 2 at. % and a slab geometry are shown experimentally to allow scaling of a single gain unit to output powers of ∼70 W, limited by the available pump power, and a strategy for scaling well beyond 100-W output is discussed. PACS 42.55.-f; 42.55.Xi; 42.60.By     

Coherent combination of high-power, zigzag slab lasers

We demonstrate a scalable architecture for a high-power, high-brightness, solid-state laser based on coherent combinations of master oscillator power amplifier chains. A common master oscillator injects a sequence of multikilowatt Nd:YAG zigzag slab amplifiers. Adaptive optics correct the wavefront of each amplified beamlet. The beamlets are tiled side by side and actively phase locked to form a single output beam. The laser produces 19 kW with beam quality <2x diffraction limited. To the best of our knowledge, this is the brightest cw solid-state laser demonstrated to date.     

High-power diode-pumped continuous-wave Nd(3+) lasers at wavelengths near 1.44 microm

We demonstrate longitudinally diode-pumped operation of Nd:YAG and Nd:YAP lasers at the long-wavelength end of the (4)F(3/2) ? (4)I(13/2) transition in the eye-safe spectral region at 1444 and 1430 nm, respectively. Special crystal coatings were required for achievement of lasing at these wavelengths. Output powers of up to 4.9 and 2.2 W, with slope efficiencies of up to 22% and 8%, respectively, were achieved. Polarized operation of the Nd:YAG laser yielded output powers of 76% as compared with unpolarized operation. Because of thermal stress, both YAG and YAP crystals were fractured at roughly 25 W of absorbed longitudinal pump power.     

Compact diode end-pumped c-cut Tm,Ho:YAlO3 laser

Cryogenic temperature operation of a c-cut Tm(5%),Ho(0.3%):YAlO₃ laser end-pumping by a fiber-coupled laser-diode is reported. A 2.55 W incident pump power is used to generate 160 mW of laser output, representing a 7.1% optical-to-optical conversion efficiency respect to the incident pump power. In the experiment, three wavelengths—2.04, 2.10, and 2.13 μm oscillation have been observed simultaneously, which is agreement with the inherent a-axis polarization fluorescence spectra of Tm,Ho:YAlO₃. Also single wavelength oscillation performance has been observed which is centered at 2.13 μm.     

Study on characteristics of diode-pumped continuous-wave tunable and passively Q-switched Tm:SSO laser

In this paper, we present a diode-pumped continuous-wave tunable and Q-switched Tm:SSO laser with a semiconductor saturable absorber mirror. In continuous-wave regime, a maximum output power of 340 mW at 1,980.7 nm was obtained. With a quartz plate, wavelength-tunable continuous-wave operation was achieved from 1,922 to 2,020 nm. In Q-switched regime, a maximum output pulse energy of 14.7 μJ under a repetition rate of 800 Hz and a minimum pulse width of 7.6 μs corresponding to a repetition rate of 8.8 kHz around 1,974.4 nm were obtained from the passively Q-switched Tm:SSO laser.     

Diode pumped actively mode-locked Tm:YAlO3 laser

CW acousto-optical mode-locked diode pumped Tm:YAlO₃ laser at 1.936 μm was experimentally studied. Lasing with output power ～100 mW, pulse repetition rate 103.4 MHz and laser pulse durations in the range of 30–200 ps was realized. The problem of laser intensity stabilization is discussed.     

Efficient continuous-wave self-frequency-doubling green diode-pumped Yb:YAl(3)(BO(3))(4) lasers

Efficient cw self-frequency-doubled green laser output of 160 mW has been obtained from Yb:YAl(3)(BO(3))(4) crystal pumped by 1.4-W incident power from a fiber-coupled 976-nm laser diode. The incident-pump-power-green-output-power conversion efficiency is greater than 11.3%, and the electrical-input-green conversion efficiency is 3.9%. Tunable green output from 513.0 to 545.8 nm is also demonstrated with a quartz birefringent filter.     

High-efficiency high-power QCW diode-side-pumped zigzag Nd:YAG ceramic slab laser

A high-efficiency high-power diode-side-pumped quasi-continuous wave (QCW) Nd:YAG ceramic slab laser using zigzag optical path was demonstrated. With an integrating sphere technique, the scattering and absorption coefficient of the ceramic slab were measured to be 0.0024 and 0.0016 cm^?1 at 1,064 nm, respectively. Under a pump power of 6.69 kW, an average output power of 2.44 kW at 1,064 nm with a repetition rate of 400 Hz was achieved, corresponding to an optical-to-optical efficiency of 36.5 %. As far as we know, this is the highest conversion efficiency reported for QCW side-pumped single slab Nd:YAG ceramic laser.     

High-conversion-efficiency, diode-pumped continuous-wave Raman laser

We demonstrate a diode-pumped cw Raman laser in H(2) with photon-conversion efficiency of (66+/-8)%. Pumped by an injection-locked diode laser at 792 nm, the Stokes laser produces a peak output power of ~16mW at 1180 nm. Accompanying the high Stokes power are deviations from the existing theory, which are believed to be caused by the thermal-lensing effect of the Raman gas.     

Tm3+ cladding-doped fiber for selective wavelength filtering in high-power pump lasers

Scattering and reflection of transmission band power in a fiber amplifier cause increased bit-error rates through multiple path interference (MPI). We report a passive method for reducing MPI contributions from the front facet of a 980-nm fiber-Bragg-grating-stabilized pump laser by use of a Tm3+-doped fiber pigtail between the diode facet and the fiber Bragg grating. Optical return loss in the C band is reduced to below -30 dB.     

二极管泵浦准三能级板条固体激光器的优化设计

基于最大激光增益条件，分析和优化了二极管泵浦准三能级Yb∶YAG固体板条激光器的激光增益、板条的最佳光学长度和最佳宽度参数。结果表明：在低功率侧面泵浦条件下，板条增益介质的掺杂浓度和板条宽度满足一定的关系，这为研究该类激光器提供了一条有效途径，其结果可应用于其他准三能级固体激光器设计。     

Rotating-disk diode-pumped continuous-wave Nd:YAG laser

Continuous-Wave (CW) diode-laser-pumped experiments using rotating Nd: YAG disk(s) have been performed in the input-power range of 1–6 W and rotation-speed range of 0–25 Hz. With a single Nd: YAG disk in the laser cavity, about 1.56 W of output power at 1.06 µm due to the Nd³⁺ (⁴ F _3/2–⁴ I _11/2) transition at an absorbed input power of 4.2 W has been observed, leading to an optical-to-optical conversion efficiency of over 37% and slope efficiency of 52% using 7.5% transmission output coupler. The laser output power has been observed to decrease by either increasing the number of Nd:YAG disks in the cavity or increasing the rotation speed of the disk(s).     

High-power diode-pumped Tm:YLF laser

A high-power, continuous-wave 3.5% Tm³⁺ doped LiYF₄ (Tm:YLF) laser has been developed. Using two Tm:YLF rods in a single cavity, 55 W of laser output at 1910 nm was obtained with a slope efficiency of 49%. The M² factor was found to be <3. With a single Tm:YLF rod, a maximum laser power of 30 W was obtained with a slope efficiency of 50%. The laser was tuned to the peak absorption wavelength of Ho:YAG of 1907.5 nm by an intracavity quartz etalon with an output power loss < 1 W. PACS 42.55.-f; 42.55.Xi; 42.60.Pk     

LiGdF4:Tm3+: spectroscopy and diode-pumped laser experiments

A novel LiGdF₄ crystal doped with Thulium ions has been grown using the Czochralski technique. Three samples with doping concentrations of 0.3 at.%, 8 at.%, and 12 at.% have been extensively spectroscopically analyzed. We also performed room-temperature preliminary laser experiments, pumping the samples with a laser diode at 792 nm obtaining 53% as maximum slope efficiency with a maximum output power of 205 mW and a minimum lasing threshold of 22 mW. The laser emission spectrum in free running condition typically spans between 1990 and 2018 nm.     

Efficient 1 W continuous-wave diode-pumped Er,Yb:YAl3(BO3)4 laser

We report the spectroscopy and high-power continuous-wave (CW) diode-pumped laser operation of Er:Yb:YAl3(BO3) crystal. Absorption and stimulated emission spectra, emission lifetimes, and efficiency of energy transfer from Yb3+ to Er3+ ions were determined. A CW Er:Yb:YAB laser emitting at 1602, 1555, and 1531 nm with output power as high as 1W and slope efficiency up to 35% was demonstrated.     

High power and efficiency of a 2044-nm c-cut Tm, Ho:YAlO3 laser

A high power and efficiency of c-cut Tm, Ho:YAlO₃ (YAP) laser is reported in the paper. The laser operated in continuous wave (CW) mode or Acousto-optical (AO) Q-switched mode at 2044 nm. The Tm, Ho:YAP crystal was cooled at the temperature of 77 K and pumped by a fiber-coupled laser diode (LD) with the centre output wavelength of 794.8 nm. In CW operation, a 9.30-W output power was obtained at a 150-mm physical cavity length, corresponding to a slope efficiency of 42.5%. In Q-switch mode, the output average power of 9 W was achieved at the pulse repetition frequency (PRF) of 10 kHz with a 130-ns pulse width. Moreover, the energy per pulse of 3.54 mJ in 47 ns was acquired at 2.5 kHz with a 75.3-kW peak power.