Judd-Oflet analysis of spectrum and laser performance of Ho:YAP crystal end-pumped by 1.91-μm Tm:YLF laser

The Ho：YAP crystal is grown by the Czochralski technique. The room-temperature polarized absorption spectra of Ho：YAP crystal was measured on a c-cut sample with 1 at% holmium. According to the obtained Judd-Ofelt intensity parameters Ω2 = 1.42 × 10^-20cm^2, Ω4 = 2.92 ×10^-20 cm^2, and Ω6 =1.71 ×10^-20cm^2, this paper calculated the fluorescence lifetime to be 6 ms for ^5I7→^5Is transition, and the integrated emission cross section to be 2.24 × 10^-18 cm^2. It investigates the room-temperature Ho：YAP laser end-pumped by a 1.91-μm Tm：YLF laser. The maximum output power was 4.1 W when the incident 1.91-μm pump power was 14.4W. The slope efficiency is 40.8%, corresponding to an optical-to-optical conversion efficiency of 28.4%. The Ho：YAP output wavelength was centred at 2118 nm with full width at half maximum of about 0.8nm.

Experimental Study on a Passively Q-Switched Ho:YLF Laser with Polycrystalline Cr2+:ZnS as a Saturable Absorber

Output performance of a continuous-wave TIn：YAP laser pumped passively Q-switched Ho：YLF laser is demon- strated with a polycrystalline Cr2＋ ：ZnS as the saturable absorber. We compare the experimental results at the three different distances L of the polycrystalline Cr2＋ ：ZnS saturable absorber to the output coupler. The pulse width almost remains constant for different L, when the incident pump power is changed in the range of 7.9 27.1 W. The shortest pulse duration of 33.3 ns for L = 105 mm and the highest average output power of 6.8 W for L = 5 mm are obtMned at the incident pump power of 27.1 W. The output wavelength of the passively Q-switched laser shifts to 2045.2nm from 2064.7nm in the cw operation. The beam quality factor of M2 is 1.2.

A 60 W Tm:YLF Laser with Triple Tm:YLF Rods

A narrow linewidth stable high-power continuous-wave 3.5% Tin3＋ doped LiYF4 （Tm：YLF） laser is reported. By using dual F P etalons and three Tm：YLF rods in a cavity, laser output of ~60 W at 1907.7nm is obtained with a slope efficiency of 34.8%. The M2 factor is found to be ~2.0 under an output power of 30 W. In addition, the relaxation oscillation and efficiency of the Tm：YLF laser are also studied. The relaxation oscillation of the Tm：YLF laser is improved obviously by setting the ratio of pump beam to oscillating laser beam as ~1.5：1 and the efficiency is increased in comparison with the ratio of ~1.3：1.

Efficient Diode-End-Pumped Actively Q-Switched Nd:YLF/SrWO4 Raman Laser

An efficient diode-end-pumped actively Q-switched Nd：YLF/SrW04 Raman laser is demonstrated. The fun- damental wave is 1047.0nm and the corresponding first-Stocks wave is 1158.7nm. With a pumping power of 10.5 W, the average output power of 2.2 W at 1158.7nm is obtained, with the corresponding optical conversion efficiency of 20.9%. At a repetition rate of 6 kHz, the pulse width of the Raman laser is 8. 7ns and the peak power is calculated to be 42.1 kW. The beam quality factors M2 in horizontal and vertical directions are 1.3 and 1.5, respectively.

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 efflciencies of 37.9% and 26.6%, respectively.

A Laser-Diode-Pumped Widely Tunable Single-Longitude-Mode Tm：YAP Laser at Room Temperature

A laser-diode-pumped widely tunable single-longitude-mode TIn：YAP laser in 2μm eye-safe region is built. Con- tinuous tanable range from 1899nm to 2025nm is achieved with the maximum laser output power of 225mW at 1989 am. In addition, the TIn：YAP laser operating under multimode and slngle-mode conditions is discussed.

Diode-pumped single frequency Tm,Ho:YLF laser at room temperature

A diode-pumped single frequcncy Tm,Ho：YLF laser operating at an eye-safe wavelength of 2 μm has been developed. Temperature of the laser crystal was controlled at room temperature with a thermoelectric cooler. The line-width narrowing elements were two solid uncoated fused silica etalons whose thicknesses were 1 and 0.1 mm, respectively. Continuous wave single frequency power of 113 mW was obtained.

Diode-pumped Nd:YLF slab master oscillator power amplifier laser system with 655 m J output at 50 Hz repetition rate

A laser-diode-pumped high-pulse-energy Nd：LiYF4 master oscillator power amplifier 1053 nm laser system is demonstrated. We design a home-made pump module to homogenize the pump intensity through the ray tracing method. To increase the extraction efficiency, the pre-amplifier adopts a double-pass amplification structure. At a repetition rate of 50 Hz, 655 mJ pulse energy and 12.9 ns pulse width of 1053 nm laser is obtained from the master oscillator power amplifier system. The corresponding peak power is 51 MW. The optical-to-optical efficiency of the system is about 9.7%.

Generation of high power laser at 1314 nm from a diode-side-pumped Nd:YLF module

We demonstrate a high power continuous-wave （CW） and acoustic-optically （AO） Q-switched 1314-nm laser with a diode-side-pumped Nd：YLF module. A maximum CW output power of 21.6 W is obtained with a diode pump power of 180 W, corresponding to an optical-to-optical conversion efficiency of 12.0% and a slope efficiency of 16.1%. In the Q-switching operation, a highest pulse energy of 3.8 mJ is obtained at a pulse repetition rate of 1 kHz. The shortest pulse width and maximum single peak power are 101.9 ns and 37.3 kW, respectively.

Efficient and compact diode-end-pumped conductively cooled Q-switched Nd:YLF laser operating at 527 nm

A novel, compact diode-end-pumped conductively cooled Q-switched Nd：YLF laser is developed. A diode-end-pumped pair of Nd：YLF slabs and an intracavity-frequency-doubled configuration are adopted to increase conversion efficiency. Using 49.8-mJ incident pump pulse energy at 500-Hz repetition rate, the laser obtains 11-mJ pulse energy and 5.5-W average output power at 527-nm wavelength, achieving an optical-optical conversion efficiency of 22%. The pulsewidth is less than 15 ns, and the beam quality factors are Mx2=1.28 and M y^2=1.12.

202 W dual-end-pumped Tm:YLF laser with a VBG as an output coupler

We demonstrated a 202 W Tm:YLF slab laser using a reflecting volume Bragg grating(VBG)as an output coupler at room temperature.Two kinds of active heat dissipation methods were used for the VBG to suppress the shift of wavelength caused by its increasing temperature.The maximum continuous wave(CW)output power of 202 W using the microchannel cooling was obtained under the total incident pump power of 553 W,the corresponding slope efficiency and optical-to-optical conversion efficiency were 39.7%and 36.5%,respectively.The central wavelength was 1908.5 nm with the linewidth(full width at half maximum)of 0.57 nm.Meanwhile,with the laser output increasing from 30 to 202 W,the total shift was about 1.0 nm,and the wavelength was limited to two water absorption lines near 1908 nm.The beam quality factors M;were measured to be 2.3 and 4.0 in x and y directions at 202 W.

Graphene oxide for diode-pumped Tm:YLF passively Q-switched laser at 2 μm

A diode-pumped Tm：YLF passively Q-switched laser at 2 μm was first demonstrated by using graphene oxide（GO） as a saturable absorber（SA）.In this letter,continuous-wave（CW） laser and pulse laser performances were studied meticulously and systematically.It reasonably showed the dependence of the pulse duration,pulse energy,and pulse repetition rate on the absorbed power.A maximum repetition rate of 38.33 kHz and a single pulse energy of 9.89 μJ were obtained.

Microperforation of the human nail plate by radiation of erbium lasers

The nail plate forms a barrier that limits the effectiveness of drug delivery in the treatment of nail diseases and prevents the outflow of fluid in the case of subungual hematoma formation. Microperforation of the nail plate through laser radiation can increase the effectiveness of drug delivery and ensure the possibility of blood outflow. This study detected and identified the type and threshold of effects that arise from exposing the nail plate to Yb,Er： Glass （λ = 1.54 μm） and Er：YLF （λ= 2.81 μm） laser radiation. The rate and efficiency of nail plate ablation by the radiation of these lasers were studied. The effect of the storage time of a freshly extracted nail plate in open air on its ablation rate by Er：YLF （ λ=2.81 μm） laser radiation was also investigated. The impact of the Yb,Er：Glass and Er：YLF laser pulses on the nail plate caused bleaching, carbonization, ablation with microcrater formation, and microperforation. The laser energy densities WE （thresholds） required for these effects were determined. The maximum ablation rate for Yb,Er：Glass laser radiation was 8 μm/pulse at WE = 91 ±2 J/cm2, whereas that for Er：YLF laser radiation was 12 μm/ pulse at WE= 10.5＋0.5 J/cm2. The maximum ablation efficiency for Yb,Er：Glass laser radiation was 0.1 μm/mJ at Ws = 10.5±0.5 J/cm2, whereas that for Er：YLF laser radiation was 4.6 μm/mJ at WE = 5.3±0.3 J/cm2. The laser ablation rate depends on the storage time and conditions of the freshly extracted nail plate. For example, when exposed to Er：YLF laser radiation, the laser ablation rate decreased by half from the initial maximum value in 96 h of air storage and returned to the initial value after 1 h of storage in distilled water.