High-energy picosecond Nd:YVO4 slab amplifier for OPCPA pumping

We demonstrate 12-ps pulses with up to 0.6-mJ pulse energy at repetition rates of 50 kHz and 100 kHz from a Nd:YVO₄ slab amplifier built in a simple four-pass configuration. Excellent noise performance with pulse energy fluctuations below 0.8% rms has been achieved by using 10-μJ seed pulses from a highly stable industrial laser system and moderate gain (30–46) in the slab amplifier.     

4程放大光路自动准直系统研究

 激光束光路自动准直系统用于神光 Ⅲ原型装置光束精密准直。针对神光-Ⅲ原型的总体要求和主光路，结合光路自动准直的关键技术，充分考虑了其4程放大主空间滤波器的4个小孔空间分布和光学位置的特点，利用小孔像传递的原理，设计出一套优化、合理的4程放大的光路准直总体方案，并且在多程放大实验平台上得到了充分的验证和考核。     

包含波面校正的四程放大系统的准直问题研究

为了解决高功率激光系统中, 尤其是多程放大系统中波前畸变校正和光路准直之间的相互干扰问题, 针对包含自适应光学系统的四程放大系统, 利用菲涅耳衍射积分理论, 建立了310 mm×310 mm大口径光束的四程传输模型, 采用坐标扩展变换的方法解决了传统计算中同时需求近、远场高分辨率带来的计算量过大问题; 基于此模型, 比较了质心法、圆拟合法和纯相位匹配滤波等三种图像处理算法对存在波面差的光束的远场中心的处理精度; 分析了波面校正对焦斑位置的影响; 本文内容为四程放大系统准直调整方案的优化提供了重要依据. 关键词： 光束准直 坐标扩展变换 自适应光学 四程放大     

Generation of 220 mJ nanosecond pulses at a 10 Hz repetition rate with excellent beam quality in a diode-pumped Yb:YAG MOPA system

A novel all-diode-pumped master oscillator power amplifier system based on Yb:YAG crystal rods has been developed. It consists of a Q-switched oscillator delivering 3 mJ, 6.4 ns pulses at a 10 Hz repetition rate and an additional four-pass amplifier, which boosts the output energy to 220 mJ, while a close to TEM(00) beam quality could be observed. Additionally a simulation of the amplification was written that allows for further scaling considerations.     

四程放大系统腔镜位置变形镜的面形解

 根据在大型高功率固体激光装置中自适应光学技术的应用研究，将变形镜置于腔镜位置，有利于提高自适应光学系统的校正动态范围。基于变口径90°翻转四程放大系统的光路特点，从理论上比较完整地解决了四程放大系统腔镜位置变形镜面形解的存在性问题，并对口径变换比值(缩束比)与面形求解之间的关系问题进行了数值模拟，结果表明:只要缩束比小于1，对应系统连续波前畸变的腔镜位置面形解是存在的，且随着缩束比减小，解的收敛性增强。     

High-Power CO2 Laser System with Repetition Rate Operation for High Current Multicharged Heavy Ion Generations

Experimental and numerical calculation results devoted to development of an optical system for an ion source based on a repetition rate CO₂ laser are described. The laser chain consists of a master oscillator, gas absorber cells, and a four-pass amplifier. The optical system provides smooth laser pulses with variable duration and high spatial quality that ensures efficiency for plasma heating and ion generation. The parameters of the plasma ion component measured in the CERN laboratory are applied for a lead target illumination.     

Development of a high-contrast,high-peak power,Ti:Sapphire/OPCPA laser system

We report on a high-contrast, high-peak power laser system, which combines both conventional laser amplification and optical parametric chirped pulse amplification (OPCPA) techniques. By employing an OPCPA system after a regenerative amplifier, we have enhanced the prepulse contrast by six orders of magnitude. A prepulse contrast of better than 4.4 × 10^?11 has been measured with a high-energy broadband pulse of 24 mJ at a 10 Hz repetition rate from the OPCPA system. With a subsequent four-pass Ti:sapphire amplifier, we have achieved an amplified energy of 279 mJ and an ultrashort recompressed amplified pulse duration of 23.5 fs. We also discuss the basic design aspects and present our preliminary experimental investigations for higher energy operation to a multijoule.     

1 J,1 Hz lamp-pumped high-gain Nd:phosphate glass laser amplifier

We present a lamp-pumped Nd: phosphate glass laser amplifier delivering up to 1 J of pulse energy at 1053 nm with a repetition rate of 1 Hz and an injected pulse energy of 2.5 mJ. The amplifier system employs a beamshaping module and a four-pass, lamp-pumped amplifier. The thermally induced wavefront distortion is mitigated and a uniform gain distribution is obtained by a four-lamp-pumped laser head in the amplifier. Thus,an excellent beam quality is obtained.     

A compact subnanosecond high power Nd:YAG laser system

In this paper, a high power Nd:YAG laser system is described, which consists of an actively-passively mode-locked Nd:YAG laser oscillator with variable subnanosecond pulsewidths (200 ps to 1 ns), a Pockels-cell shutter and a coaxial four-pass Nd:YAG amplifier. With the oscillator operating in the colliding pulse regime, and a BDN dye film as the saturable absorber, and an acousto-optic modulator as the active modelocker, we have achieved a shot-to-shot stability of the pulse-train amplitude < ±4%. For a 0.1 mJ, 200 ps laser pulse, we obtained four-pass amplification of 7 × 10² with a pump energy of 106 J.     

Generation of near-Fourier-transform-limited high-energy pulses in a chain of fiber-bulk amplifiers

We demonstrate the generation of high-power near-Fourier-transform-limited pulses with variable pulse duration in the nanosecond regime through a combination of fiber and bulk amplification. The fiber amplifier consists of a dual-stage fiber amplifier based on Nd- and Yb-doped single- and double-clad fibers. The bulk amplifier consists of a four-pass, flash-lamp-pumped Nd:YAG rod. Since no resonance condition is required for locking of the seed source to a slave cavity, the setup is extremely rugged.     

Demonstration of a compact 100 Hz, 0.1 J, diode-pumped picosecond laser

We have demonstrated an all-diode-pumped Yb:YAG chirped pulse amplification laser that produces 100 mJ pulses of 5 ps duration at 100 Hz repetition rate. The compact laser system combines a room-temperature Yb:YAG regenerative amplifier for increased bandwidth and a cryogenically cooled Yb:YAG four-pass amplifier for improved heat dissipation and increased efficiency. The optical efficiency of this amplifier is higher than that of other diode-pumped systems of comparable energy.     

四程放大自动准直系统数学模型研究

针对高功率激光装置四程放大系统的特点,利用矩阵光学原理,建立了四程放大准直系统的数学模型;基于此模型,设计了四程放大系统的准直调整方案;得出了近、远场偏移量与调整量关系的解析解. 关键词： 激光技术 光束准直 四程放大     

A Compact All-Solid-State 630-ps 9.43-kHz High Power Nd：YAG/Nd：YVO4 Hybrid Laser System

We present a simple and compact design for an all-solid-state laser amplifier system which can output 9.43-kHz 630-ps, 3.5-W pulse trains under 20 W absorbed pumping power. The excellent matching between the repetition of its seed source and the fluorescence lifetime of the amplifying medium makes it quiet efficient for the four-pass amplifier to be pumped in cw mode without need of any synchronization device between the oscillator and the amplifier. The entire setup just covers an area of 55 × 25 cm^2. The output average power fluctuation is less than ±1.5% within 10min and 3% within 6h.     

Chirped-pulse amplification of ultraviolet femtosecond pulses by use of Ce(3+):LiCaAlF(6) as a broadband, solid-state gain medium

Chirped-pulse amplification in the ultraviolet region is demonstrated by use of a broadband Ce(3+): LiCaAlF(6) laser medium. A modified bow-tie-style four-pass amplifier pumped by 100-mJ, 266-nm pulses from a Q -switched Nd:YAG laser has a gain factor of 370 and delivers 6-mJ, 290-nm pulses. After dispersion compensation, the output pulses can be compressed to 115 fs.     

Highly efficient degenerate four-wave mixing with multipass geometries in a polymer laser dye saturable amplifier

We demonstrate the use of highly efficient degenerate four-wave mixing for phase conjugation with multipass geometries in a polymer laser dye saturable amplifier. Phase-conjugate energy reflectivity of as much as 20,000% with a four-pass geometry in the longitudinally pumped polymer dye was obtained at 564 nm.     

Applying the stochastic parallel gradient algorithm in the auto alignment problem for the amplifier channel of the UFL-2M facility

The procedure of automatic alignment of the four-pass amplifier channel of a UFL-2M facility has been simulated numerically in the presence of aberrations in the optical path. The alignment procedure is based on the “marker” or “reference” method. The control elements are directed by the stochastic parallel gradient algorithm. The order of executing the automatic alignment is determined. The numerical simulation shows the possibility of positioning the beam at the exit from the channel with an accuracy of 1% of the pinhole size in the far field and of 0.1% of the beam aperture size in the near field. It was established that the centering accuracy of the alignment beam in inner pinholes in the presence of optical inhomogeneities in the amplifier channel can be worse than at the exit of the channel. The possibility of symmetrizing the picture of far-field markers has been considered in the case where the position of the optical axis of the channel is unknown.     

Multifunctional high-performance 10-J level laser system

In this letter,we report a multifunctional high-performance Nd:glass laser system.Laser pulses from an all-fiber front end are first amplified by a regenerative amplifier to 10 mJ level,and then further amplified in a four-pass amplifier.The laser system can provide 10.3-J,3-ns laser pulses at 1053-nm wavelength.The shot-to-shot energy stability is better than 1.5%(RMS).The output laser beam is near diffraction limit.Binary amplitude masks are used to maintain a flat top near-field profile with a 71%fill factor.After the frequency conversion process,7 and 5.5 J pulses at 526.5 and 351 nm are obtained,respectively.     

Beam stability analysis of high power laser system based on relay imaging

The model of a beam propagating in a high power laser system is built based on relay imaging. The displacement sensitivity of the lens to beam positioning error is obtained using this model, which is then compared with the traditional method. Two real systems, the pre-amplifier and four-pass amplifier in SGII-U, are presented to further discuss the differences between the two methods. The limitation and application range are summarized in the end. The findings can be used to provide guidance in similar systems.     

A 61-mJ, 1-kHz cryogenic Yb: YAG laser amplifier

We report a diode-pumped rod-type Yb:YAG laser amplifier operating at 1 kHz. Cryogenic cooling method was adopted to make the Yb:YAG crystal work with four-level behavior. A single-frequency fiber laser acts as the seed in an actively Q-switched Yb:YAG oscillator. The resonator delivers 5.75-mJ pulses at 1 kHz with a pulse duration of approximately 40 ns. The pulses were amplified to 61 mJ in a four-pass rod-type Yb:YAG amplifier with optical-to-optical efficiency of 24% in the main amplifier. The M² parameter of the output laser is <1.4.     

Experimental study of a broad-band XeCl double-pass amplifier with SBS mirror

An oscillator-amplifier XeCl laser system has been used to experimentally investigate the effectiveness of a liquid stimulated Brillouin scattering (SBS) mirror for correcting the spatial aberrations of broad-band laser radiation in a double-pass amplifier. It has been found that the SBS amplifier performance is strongly dependent on the intensity I _p exciting the Brillouin medium. A good beam reconstruction has been attained at I _p1GW/cm², whereas highly aberrated output beams have been delivered by the SBS amplifier for I _p>1 GW/cm². By comparing the broad-band SBS amplifier performance to that of the same amplifier with a dielectrically coated flat mirror at one end, it has been found that the use of a SBS mirror is advantageous to obtain lower divergence output beams only for low energy pump beams (<1 mJ).