High beam quality by SBS phase conjugation of a single rod Nd-amplifier up to 140 W average output power

For pumping XUV plasma light sources with solid-state lasers and also for micromaterial processing, high beam quality and output power as well as simplicity of the pump lasers are crucial. The beam quality of high-power solid-state lasers can be significantly improved using phase-conjugating mirrors based on stimulated Brillouin scattering (SBS). Hence, SBS phase conjugation may prove one of the key technologies in this field. We describe a single-rod neodymium amplifier with 140 W average output power and nearly diffraction-limited beam. Because of automatic compensation of the thermal lensing by SBS phase conjugation, the output power can be tuned without changing the beam profile.     

Self-Frequency-Doubling Ytterbium Lasers

Ytterbium-doped self-frequency-doubling lasers offer high efficiency, tunable, visible and near-infrared, cw and pulsed operation from compact devices. We review the performance of ytterbium-doped yttrium aluminium borate (Yb:YAB) self-frequency-doubling lasers. Because of the detailed dynaMisc of the interaction of the nonlinear pulse shaping process for mode-locking or for Q-switching self-frequency-doubled lasers, we observe pulse lengthening in each process when frequency doubling is optimised, with high average output power. However, for continuous wave operation, the self-frequency doubling process may be optimised to give highly efficient, robust, widely-tunable output in the visible as well as fundamental output in the infrared.     

InAs/GaAs quantum-dot saturable absorber for a diode-pumped passively mode-locked Nd:YVO4 laser at 1342 nm

We report that InAs/GaAs quantum dots were developed to be saturable absorbers as well as output couplers in diode-pumped passively mode-locked Nd:YVO4 lasers at 1342 nm. With an incident pump power of 12.6 W, an average output power of 0.85 W with a mode-locked pulse width of 26 ps at a repetition rate of 152 MHz was obtained.     

Soliton mode-locked Er:Yb:glass laser

We report on a simple diode-pumped passively mode-locked Er:Yb:glass laser generating transform-limited 1536-nm solitons of 255-fs duration with a repetition rate of 50 MHz and average power of 58 mW. We also discuss timing jitter and the trade-off between short pulses and high output power in these lasers.     

High power ultrafast Nd:YVO<Subscript>4</Subscript> laser mode locked by single wall carbon nanotube absorber

We use a single walled carbon nanotubes (SWCNTs) absorber to demonstrate a high power mode locking for Nd:YVO₄ lasers. Under the pump power of 12 W, continuous wave mode-locked (CWML) pulse were generated with the maximum average output power of 3.6 W and the pulse duration of 7.6 ps. The peak power and the single pulse energy of the mode-locked laser were up to 4.9 kW and 37.5 nJ, respectively. To our knowledge, this is the highest average output power of the CWML laser with the SWCNTs absorber reported.     

1018 nm短波长掺镱光纤激光高功率自组织相干合成

搭建了两台高功率、低量子损耗的1018 nm短波长掺镱光纤激光器,进行了全光纤结构下两路光纤激光器的相干合成实验。获得了功率为55 W、合成效率为90.2%的相干输出,这是当前严格单模1018 nm光纤激光器的最高功率水平。同时,验证了Michelson腔自组织相干合成技术能够实现光纤激光器的高功率单模输出。     

体布拉格光栅用于高功率光谱组束的研究

使用透射型体布拉格光栅组束两束光纤激光,实现了856 W光谱组束输出。总的光谱组束效率为73.7%,组束光束的横向质量因子为7.9,纵向质量因子为2.7。研究结果显示,虽然体光栅的角色散严重影响衍射光束的光束质量,但其并不影响透射光束的光束特性。由于当前宽谱光纤激光器的输出功率远大于窄线宽输出,使用宽谱光纤激光器(光谱带宽超过4nm)作为透射光束,能够在不降低组束效率和组束光束质量的前提下,有效提升使用体布拉格光栅进行光谱组束的总输出功率。     

基于89C52的Cr,Tm,Ho∶YAG激光治疗机控制系统的设计

介绍了Cr,Tm,Ho∶YAG激光治疗仪控制系统。通过89C52单片机实现了脉冲激光电源分频电路的控制,通过该芯片控制步进电机驱动器以及脉冲激光电源实现了四路Cr,Tm,Ho∶YAG激光的轮流输出,耦合了一根320μm的低OH-石英光纤,目前的输出功率在国内处于领先水平。     

High-energy, high-power ytterbium-doped Q-switched fiber laser

We report on a Q -switched, cladding-pumped, ytterbium-doped large-mode-area fiber laser operating at 1090 nm that is capable of generating 2.3 mJ of output pulse energy at a 500-Hz repetition rate and more than 5 W of average output power at higher repetition rates in a high-brightness beam (M(2) = 3) . Using a similar fiber with a smaller core, we generated >0.5-mJ pulses in a diffraction-limited beam. Our results represent a threefold increase in pulse energy over previously published values for Q-switched fiber lasers and firmly establish fiber lasers as compact, multiwatt, multimillijoule pulse sources with large scope for both industrial and scientific applications.     

飞秒光纤激光相干合成技术最新进展

飞秒光纤激光器具有平均功率高、散热性能佳、光束质量好和空间体积小等优势,在基础研究、工业加工、生物医疗等方面得到越来越广泛的应用.相干合成技术能够有效克服光纤中有害的非线性效应和热效应的影响,进一步提高飞秒光纤激光器输出的脉冲能量和平均功率.本文介绍高功率飞秒光纤激光器相干合成的基本技术路线,重点阐述相干合成技术中关于填充孔径相干合成与平铺孔径相干合成的最新研究进展,并详细介绍相干合成技术中不同类型主动相位锁定技术的基本原理.相信在不远的将来,飞秒光纤激光相干合成系统的单脉冲能量和平均功率将不断攀升,从而开创许多崭新的研究领域.     

Optical parametric oscillators for high pulse energy and high average power operation based on large aperture periodically poled KTP and RTA

We report on optical parametric oscillators (OPOs) based on large aperture periodically poled KTiOPO₄ (PPKTP) and RbTiOAsO₄ (PPRTA) pumped with high pulse energy and high average power Q-switched solid-state lasers. The OPOs were pumped with 1064-nm pulses of a diode-pumped Nd:YVO₄ laser at 20 kHz repetition rate. The emitted signal wavelengths were 1.72 μm and 1.58 μm and the idler wavelengths were 2.79 μm and 3.26 μm, respectively. Pumping the PPKTP OPO with 7.2 W and the PPRTA OPO with 8 W average power, 2 W and 1.3 W total OPO output powers were generated. Two-dimensional measurements of the total OPO output power, the signal wavelength and the signal bandwidth in dependence on the crystal location indicated a good uniformity of the quasiphasematching structure over the entire 3-mm-thick crystals. This allowed pumping with larger pump beams and therefore with pulse energies of tens of millijoules. Pumping with different flash-lamp-pumped lasers, good OPO performance and high output pulse energies could be achieved for all pump lasers. Maximum input pulse energies of 56 mJ gave output pulse energies of as much as 18 mJ. The temperature tuning behaviors of both OPOs were measured, showing excellent agreement with calculated temperature tuning curves. New equations for temperature dispersion in RTA are presented. These results show that large-aperture PPKTP and PPRTA crystals are well suited for tunable nanosecond OPO operation with multi-watt average pump power and several tens of millijoules pump pulse energies. Received: 7 September 2001 / Published online: 7 November 2001     

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.     

External resonator design for high-power laser diodes that yields 400mW of TEM(00) power

Normal diode lasers with average output powers of 1 W or more exhibit bad beam quality and therefore cannot be applied for high-precision applications or nonlinear optics. Therefore an external output coupling mirror was used in our experiments. Diffraction-limited operation was achieved, which yielded 400 mW of power and a factor-of-12 improvement in brightness. With this resonator type 1.1 W of average output power was also obtained, with a beam propagation factor of 2.6 in the slow axis; fast axis emission is always diffraction limited.     

Characteristics of copper HyBrID-type lasers which use HCl reactive gas

We have investigated the output behaviour of a low temperature HyBrID-type copper laser operating with a flowing Ne–HCl reactive gas mixture. 15.5 W of average power was observed from a 19 mm bore device at 23 kHz PRF corresponding to a specific output power of 78 mW/cm3. The output power was 20–30% lower than that of the same device operating with an Ne–HBr mixture; however, it markedly exceeds the output of similar sized elemental copper vapour lasers (with or without hydrogen additive). This revised version was published online in June 2006 with corrections to the Cover Date.     

High-energy soliton pulse generation with a passively mode-locked Er/Yb-doped multifilament-core fiber laser

We report the generation of high-energy short pulses from a mode-locked erbium/ytterbium-doped large-mode-area multifilament-core fiber laser operating in the purely anomalous dispersion regime. The self-starting fiber laser emits 400 mW of average output power at a pulse repetition rate of 44 MHz, corresponding to a pulse energy of 9.1 nJ. The laser produces near transform-limited output pulses with pulse duration of 1.6 ps, corresponding to 5 kW peak power. This new type of low-nonlinearity fibers demonstrates the power and energy scaling potential of fiber-based short pulse lasers in the eye-safe region.     

Passively mode-locked Nd:LuVO(4) laser with a GaAs wafer

We report on the passive mode locking of a diode-pumped Nd:LuVO(4) laser with a GaAs wafer as output coupler. Using the interference modulation effect of the GaAs wafer, high-power continuous-wave mode locking with a pulse width of about 7.1 ps and an average output power of 3.11 W was achieved. Our result shows that Nd:LuVO(4) could be an excellent gain medium for diode-pumped high-power mode-locked lasers.     

14-fs pulse generation in Kerr-lens mode-locked prismless Cr:LiSGaF and Cr:LiSAF lasers: observation of pulse self-frequency shift

Kerr-lens mode-locked Kr-laser-pumped Cr:LiSGaF and Cr:LiSAF lasers containing only two newly developed low-loss chirped mirrors instead of conventional dielectric resonator mirrors and generating pulses of widths as small as 14-fs with as much as 100 mW of average output power are reported. We report what is to our knowledge the first experimental observation of a pulse self-frequency shift in crystalline active media that are characteristic of such short pulses at megawatt intracavity peak powers. We also believe this phenomenon to be one of the significant limiting factors for pulse duration in femtosecond Cr:LiSAF-type lasers.     

Mode-locked self-starting Cr:forsterite laser using a single-walled carbon nanotube saturable absorber

We report what we believe to be the first passive mode-locking of Cr:forsterite laser using a single-walled carbon nanotube saturable absorber (SWCNT-SA). The dispersion-compensated Cr:forsterite laser in a self-starting configuration produces nearly Fourier transform-limited pulses as short as 120 fs near 1.25 microm. The maximum average output power of 202 mW obtained with a 5% output coupler at a repetition rate of 79.1 MHz represents, to the best of our knowledge, the highest power level ever reported for SWCNT-SA mode locking of solid-state lasers.     

Acousto-Optic Power Summation for Mutually Noncoherent Pulsed Lasers

A method of the power summation for mutually noncoherent pulsed lasers of the same type using time interleaving is proposed and validated experimentally. The method uses an acoustic-optic deflector, which commutates radiation of different sources into one output channel simultaneously with radiation presenting in this channel. It is crucially important that the power of the final output radiation is equal to the power sum of the input sources, and the angular and coordinate parameters of an output beam are the same as that for the input sources. The experiments were carried out with single-mode diode lasers on a wavelength of 1.3 μm using a ТеО₂-crystal-based deflector. The method is appropriate for the power summation for fiber-optic, diode, and solid-state lasers. We have estimated the main interrelated parameters.     

1.1-W cw Cr:LiSAF laser pumped by a 1-cm diode array

We demonstrate 1.1-W cw output power from a diode-laser array-pumped Cr:LiSAF laser based on a concept that allows for pumping low-gain solid-state lasers at reduced temperature rise. We discuss scaling to higher powers as a function of diode power and define a figure of merit for evaluating given diode lasers as pump sources for low-gain solid-state lasers.