Compact high-power end-pumped Nd:YAG laser

We present a compact diode- and end-pumped Nd:YAG laser for material processing with an output power of 238 W, an optical-to-optical efficiency of 48% and a slope efficiency of 60%. This is to the best of our knowledge the highest optical efficiency for a high-power end-pumped Nd:YAG laser.     

Experimental study of high-power pulse side-pumped Nd:YAG laser

The paper reports on the characterization of a compact and simple side-pumped 0.538 J×100 Hz pulse Nd:YAG laser. A side-pumping configuration with 100 laser diode bars is used in the laser head. We also experimentally studied the laser performance of the diode-pumped Nd:YAG laser head in the free running and Q-switched operation under different repetition rates.     

Experimental study of electro-optical-switched pulsed Nd:YAG laser

We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd:YAG laser. We experimentally study and compare the performance of the pulsed Nd:YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configuration of the optical resonator. In this laser, an unsymmetrical concave–concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 m J with an FWHM pulse width of 7 ns at100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.     

Experimental study of a high-power CW side-pumped Nd:YAG laser

The paper reports on the characterization of a side-pumped 40 W CW Nd:YAG laser. A side-pumping configuration with six laser diodes is used for the laser. We show the comparison between the calculated and measured pump energy distributions in the laser crystal. The birefringence and the thermal lens effect of the Nd:YAG crystal have been experimentally investigated, and their influence on the performance of the laser are discussed. Output power and beam quality of the laser under different output couplings, cavity lengths, types of cavity and different temperatures of the cooling water have been experimentally studied.     

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.     

Thermal effects in high-power Nd:YAG disk-type solid state laser

An investigation of thermal effects in a high-power Nd:YAG disk-type solid state laser pumped with different pump beam transverse profiles is carried out by numerical simulation based on the finite element method (FEM). Impact of the heat sink on the thermal effects is included in the simulation. The distribution of first principle stress, thermally induced birefringence, including the distribution and variation of the birefringence loss, are studied. The characteristics of the phase variation are analyzed with consideration of the temperature gradient, deformation, strain and thermal stress. Thermal lensing is explored as a function of pump power and of the radius pumped with different pump beam transverse profiles. The non-parabolic part of optical phase distortion is simulated. Furthermore, the characteristics of the bi-focus of the disk laser are also studied. Experiments on the maximum tensile stress distribution and depolarization loss are carried out. The presented calculations are in qualitative agreement with the experimental observations.     

Experimental study of electro-optical Q-switched pulsed Nd:YAG laser

We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd:YAG laser. We experimentally study and compare the performance of the pulsed Nd:YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configuration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.     

Biocompatible film deposition by using Nd:YAG pulsed laser

A Nd:YAG laser operating at the fundamental wavelength (1064 nm) and at the second harmonic (532 nm), with 9 ns pulse duration, 100–900 mJ pulse energy, and 30 Hz repetition rate mode, was employed to ablate in vacuum (10^?6 mbar) biomaterial targets and to deposit thin films on substrate backings. Titanium target was ablated at the fundamental frequency and deposited on near-Si substrates. The ablation yield increases with the laser fluence and at 40 J/cm ² the ablation yield for titanium is 1.2×10¹⁶ atoms/pulse. Thin film of titanium was deposited on silicon substrates placed at different distance and angles with respect to the target and analysed with different surface techniques (optical microscopy, scanning electron spectrosopy (SEM), and surface profile).

Hydroxyapatite (HA) target was ablated to the second harmonic and thin films were deposited on Ti and Si substrates. The ablation yield at a laser fluence of 10 J/cm ² is about 5×10¹⁴ HA molecules/pulse. Thin film of HA, deposited on silicon substrates placed at different distance and angles with respect to the target, was analysed with different surface techniques (optical microscopy, SEM, and Raman spectroscopy).

Metallic films show high uniformity and absence of grains, whereas the bio-ceramic film shows a large grain size distribution. Both films found special application in the field of biomaterial coverage.     

高功率高光束质量脉冲Nd: YAG激光器

 以实现高功率、高光束质量的脉冲激光输出为目的,对非对称平-凹谐振腔的结构进行了理论分析。设计出了高功率、高光束质量非对称放置的平-凹谐振腔、双氙灯泵浦的脉冲Nd: YAG激光器。当占空比为9%时,实现输出激光平均功率近480 W,光束参数积优于12.7 mm·mrad,电光转化效率近4%,与理论分析吻合,可用芯径300 μm的光纤传输,不稳定性优于±1%。加工实验证明有较好的质量：切割材料为不锈钢,厚度为3 mm时、切割速度为0.6 m/min和厚度为1.5 mm、切割速度为1.2 m/min时,两种情况下所得切缝宽度均为250 μm,且切割上下沿光滑。     

Investigation of Cr:YAG passive mode-locking in a pulsed Nd:YAG laser

Passive mode-locking of a pulsed Nd:YAG laser using a Cr⁴⁺:YAG saturable absorber was realized for the first time in a nearly critical stable resonator containing an antiresonant ring structure. The output energy and pulse duration are 13.5 mJ and 180 ps, respectively. The recovery time and saturable intensity for excited-state absorption of Cr⁴⁺:YAG under the action of strong laser pulses were calculated from rate equations.     

高功率高光束质量脉冲Nd: YAG激光器

以实现高功率、高光束质量的脉冲激光输出为目的,对非对称平-凹谐振腔的结构进行了理论分析。设计出了高功率、高光束质量非对称放置的平-凹谐振腔、双氙灯泵浦的脉冲Nd: YAG激光器。当占空比为9%时,实现输出激光平均功率近480 W,光束参数积优于12.7 mm·mrad,电光转化效率近4%,与理论分析吻合,可用芯径300 μm的光纤传输,不稳定性优于±1%。加工实验证明有较好的质量：切割材料为不锈钢,厚度为3 mm时、切割速度为0.6 m/min和厚度为1.5 mm、切割速度为1.2 m/min时,两种情况下所得切缝宽度均为250 μm,且切割上下沿光滑。     

An efficient high-power 946 nm Nd:YAG planar waveguide laser

To date increasing the output power of Nd:YAG lasers operating on the three-level ⁴F_3/2→⁴I_9/2 transition has been restricted by detrimental thermal effects in the gain medium. Using a double-clad planar waveguide, an efficient 946 nm laser has been demonstrated that produced 35 W of output power with corresponding slope and optical-to-optical conversion efficiencies of 56% and 50%, respectively. Performance and further power-scaling possibilities are discussed.     

Passively mode-locked high-power Nd:YAG lasers. with multiple laser heads

We discuss power scaling of passively mode-locked lasers using multiple laser heads in the resonator. We experimentally compared two different approaches for the cavity design, both using three side-pumped Nd:YAG laser heads. We obtained a record-high average output power of up to 27 W with close to diffraction-limited beam quality, a pulse duration of 19 ps, a pulse energy of 0.5 7J, and 23 kW peak power. Single-pass second-harmonic generation in a 10-mm-long LBO crystal yields 16.2 W of 532-nm radiation.     

UV laser micromachining of piezoelectric ceramic using a pulsed Nd:YAG laser

UV laser (=355 nm) ablation of piezoelectric lead zirconate titanate (PZT) ceramics in air has been investigated under different laser parameters. It has been found that there is a critical pulse number (N=750). When the pulse number is smaller than the critical value, the ablation rate decreases with increasing pulse number. Beyond the critical value, the ablation rate becomes constant. The ablation rate and concentrations of O, Zr and Ti on the ablated surface increase with the laser fluence, while the Pb concentration decreases due to the selective evaporation of PbO. The loss of the Pb results in the formation of a metastable pyrochlore phase. ZrO₂ was detected by XPS in the ablated zone. Also, the concentrations of the pyrochlore phase and ZrO₂ increase with increasing laser fluence. These results clearly indicate that the chemical composition and phase structure in the ablated zone strongly depend on the laser fluence. The piezoelectric properties of the cut PZT ceramic samples completely disappear due to the loss of the Pb and the existence of the pyrochlore phase. After these samples were annealed at 1150 °C for 1 h in a PbO-controlled atmosphere, their phase structure and piezoelectric properties were recovered again. Finally, 1–3 and concentric-ring 2–2 PZT/epoxy composites were fabricated by UV laser micromachining and their thickness modes were measured by impedance spectrum analysis and a d₃₃ meter. Both composites show high piezoelectric properties. PACS 81.40.Gh; 77.84.-s     

Quality of the beam produced a pulsed Nd:YAG laser

The quality of the beam produced by a Nd:YAG laser was investigated. A hemispherical Nd:YAG laser resonator was developed. A flashlamp driver was designed to pump a Nd:YAG laser crystal. The output of the laser was characterized via the variation of the capacitor voltage. A phosphor card was used to detect the invisible of the infrared beam. Exposed photographic paper was utilized to examine the energetic beam after interaction. The brightness and strength of the beams were analyzed using the Matrox Inspector and VideoTest 5 software packages. The intensity of the beam produced and the volume loss after interaction were found to linearly increase with respect to the input energy.     

用倍频晶体KTP实现Nd：YAG激光锁模的研究

报道用倍频晶体KTP实现Nd:YAG激光锁模的系统研究,给出了该锁模激光器输出脉宽的表达式,并和实验测量值相比较,计算值跟实验结果符合较好.文中还分析了各种参数对该锁模激光输出性能的影响.     

高平均功率六棒串接脉冲Nd:YAG激光器

报道了一种腔内六棒串接的脉冲Nd:YAG激光器。采用44矩阵对晶体棒失调角度对谐振腔光轴的影响进行了理论分析,给出了六棒串接脉冲激光器中晶体棒失调角度的允许范围。在串接实验中,谐振腔采用对称平平腔结构,通过调整每根晶体棒的失调角度到允许范围内,实现了六棒串接脉冲Nd:YAG激光器。在输入电功率86 kW,占空比17%时,获得了平均功率3 018 W的脉冲激光输出,峰值功率17.75 kW,最高单脉冲能量为66 J,光束参数乘积为26.3 mmmrad,电光转换效率3.5%,长时间工作不稳定性小于2%。     

高平均功率六棒串接脉冲Nd:YAG激光器

报道了一种腔内六棒串接的脉冲Nd:YAG激光器。采用44矩阵对晶体棒失调角度对谐振腔光轴的影响进行了理论分析,给出了六棒串接脉冲激光器中晶体棒失调角度的允许范围。在串接实验中,谐振腔采用对称平平腔结构,通过调整每根晶体棒的失调角度到允许范围内,实现了六棒串接脉冲Nd:YAG激光器。在输入电功率86 kW,占空比17%时,获得了平均功率3 018 W的脉冲激光输出,峰值功率17.75 kW,最高单脉冲能量为66 J,光束参数乘积为26.3 mmmrad,电光转换效率3.5%,长时间工作不稳定性小于2%。