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The thermal lens effects in Tm:YAP laser are analyzed by solving the Poisson equation with finite difference method. The thermal focal lengths measured are in the range of 40 ? 90 mm at the pump power of 16?34 W, consistent with the simulation results. The temperature contribution coefficient (the linear coefficient between the maximum temperature in the laser crystal and the pump power) of 1.19 K/W is also obtained. The convex lens and plano-concave mirror thermal lens compensation methods are proposed and applied to a high power pumped Tm:YAP laser.

The active Q-switched and passive mode-locked Er3+-doped all-fibre laser is presented. The fibre laser centre wavelength is located at 1563 nm and determined by the homemade singlemulti- single (SMS) in-line fibre filter. The laser spectrum width is nearly 0.1 nm. The active Q-switched mechanism relies on the polarisation state control using a piezoelectric to press a segment of passive fibre on the circular cavity. The nonlinear polarisation rotation technology is used to realise the passive self-started modelocked operation. In the passive mode-locked regimes, the output average power is 2.1 mW, repetition frequency is 11.96 MHz, and single pulse energy is 0.18 nJ. With the 100-Hz Q-switched regimes running, the output average power is 1.5 mW. The total Q-switched pulse width is 15 us, and every Q-switched pulse is made up by several tens of mode-locked peak pulses. The calculated output pulse energy of the Q-switched fibre laser is about 15 uJ, and the energy of every mode-locked pulse is about 64-68 nJ during a Q-switched pulse taking into account the power fraction propagating between pulses.

High-efficiency continuous-wave (CW) Tm:YLF laser by the dual-end-pumping configuration is presented. Under the total input pump power of 24.0 W, the highest output power reaches 9.8 W in the wavelength range of 1910-1926 nm by use of 10% output coupling, corresponding to optical conversion efficiency of 40.9% and slope efficiency of 51.4%. The free-running laser spectrum of Tm:YLF is measured.

We report a continuous-wave (CW) 2.1-\mum Ho:YAG laser operating at room temperature pumped by a diode-pumped 1.94-\mum Tm:YAP laser. The maximum output power of 1.5 W is obtained from Ho:YAG laser, corresponding to Tm-to-Ho slope efficiency of 17.9% and diode-to-Ho conversion efficiency of 5.6%.

A low-threshold middle-infrared (mid-IR) MgO:PPLN optical parametric generation (OPG) pumped by a laser diode (LD) end-pumped Z-type Nd:YLF laser at 1047 nm is realized with high reflectivity(HR) mirror for signal. At repetition rate of 10 kHz, the OPG threshold of 50 'mu'J has been achieved with HR mirror for signal. Compared with the threshold without mirror, the threshold decreases by 17%. Using HR mirror for pump at output side of crystal, the threshold of 40 'mu'J is achieved. The 2.7-4.1 micron continuous tunable output is produced with seven grating periods from 28.5 to 31.5 micron and temperatures from 30 to 200 centigrade. When the incident average pump power is 3 W, the OPG idler output power is 0.46 W at 3.26 micron, which corresponds to optical-to-optical conversion efficiency up to 15.3%.

A doubly resonant ZnGeP2 (ZGP) optical parametric oscillator (OPO) pumped by a novel Tm,Ho:GdVO4 laser was demonstrated. Cryogenic Tm(5 at.-%), Ho(0.5 at.-%):GdVO4 laser with high pulse repetition frequency (PRF) of 10 kHz at 2.05 microns was employed as pumping source of ZGP OPO. The 15-mm-long ZGP crystal, 55° cut for I-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 4.52 ?m under pumping power of 5.3 W, corresponding to slope efficiency of 40% from incident 2-?m laser power to mid-infrared (Mid-IR) output. A widely tunable range from 3.0 to 6.5 ?m was achieved by changing the crystal angle only 3.5°.

A Nd:YAG master oscillator power amplifier (MOPA) system, pumped by a pulse flash-lamps as the pump source of optical parametric oscillator (OPO), is employed to improve the pump beam quality of OPO pump source. A back amplifying configuration with stimulated Brillouin scattering (SBS) phase conjugation mirror is used. OPO pump laser energy of 611 mJ/pulse with 30-ns pulse duration is obtained, and near diffraction limited beam quality is achieved. Based on the type II degenerate non-critically phase-matched KTP crystal, the OPO is used to convert pump beam from 1.064 ?m to 1.57 ?m, eye-safe near infrared laser range source. 1.57-?m output energy of 209 mJ/pulse with 18-ns pulse duration is attained with a short cavity KTP OPO, when pump laser energy is approximately 611 mJ. OPO conversion efficiency is up to 38.7% when pump laser energy is approximately 200 mJ.

We demonstrate a single-longitudinal-mode Ho^3+:YVO_4 unidirectional ring laser based on the acousto-optic effect, utilizing the features of the acousto-optical Q switch and half-wave plate to achieve unidirectional operation. The maximum power achieved in the single-longitudinal-mode at 2053.9 nm is 941 mW when the absorbed power is set as 4.4 W, yielding a nearly 50% slope efficiency. The M^2 factor is 1.1. The results show that such a technique offers a potentially promising new method for achieving a high power and narrow linewidth 2 μm single-longitudinal-mode laser.

We report a cladding-pumped actively Q-switched ring Tm-doped fiber laser (TDFL). This laser is Q-switched by a free space acousto-optic modulator. A pulse energy up to 150 μJ with a pulse width of 207 ns at a repetition rate of 100 Hz is achieved for a cavity optical length of 6.68 m. The pulse amplitude’s stability at this repetition rate is better than 95%. To the best of our knowledge, this is the first free space structure Q-switched ring TDFL report.

We report a monolithic Tm:YLF micro laser in this Letter. In order to improve the relaxation oscillation of the laser, both ends of the crystal are coated, making the Tm:YLF crystal itself a resonant cavity. The micro laser is pumped by a 792 nm laser diode operated in the continuous wave (CW) mode. We obtain maximum output powers of 7.78 and 10.4 W at the total incident power of 43.6 W with focus lenses of 37.5 and 40 mm, respectively, corresponding to the slope efficiencies of 25.6% and 40.0% and the optical–optical conversion efficiencies of 17.8% and 23.8%. It is clear that the amplitude of the relaxation oscillation is smaller and the beam quality is better with the focus length of 37.5 mm; however, the laser with the focus length of 40 mm produces a higher output power and a more stable wavelength centering at 1878.44 nm.

We demonstrate a diode-pump Tm^3+-doped all-fiber laser operating at 1908 nm based on a master oscillator power amplifier (MOPA) configuration. In our work, 152 W of laser output power is generated by a total incident pump power of 434 W at 790 nm, corresponding to the total optical efficiency of 35%. The laser wavelength is 1908.29 nm. To the best of our knowledge, it is the highest output power reached around 1908 nm with such a narrow linewidth of 0.18 nm based on a MOPA configuration.