PW级掺钛蓝宝石激光放大器中横向寄生振荡控制

介绍了目前世界上在建的第一台掺钛蓝宝石激光系统中大口径晶体内横向寄生振荡的抑制方法。采用一种掺炭的热塑料MeltMount 1.704作为折射率匹配材料,掺入炭粉作为吸收体。理论上它可以将晶体中的寄生振荡阈值从13增加到2100。     

PW级掺钛蓝宝石激光放大器中横向寄生振荡控制

 介绍了目前世界上在建的第一台掺钛蓝宝石激光系统中大口径晶体内横向寄生振荡的抑制方法。采用一种掺炭的热塑料MeltMount 1.704作为折射率匹配材料，掺入炭粉作为吸收体。理论上它可以将晶体中的寄生振荡阈值从13增加到2100。     

A hybrid OPCPA/Nd:phosphate glass multi-terawatt laser system for seeding of a petawatt laser

To enhance radiographic abilities on its Z-Accelerator, Sandia National Laboratories is incorporating a petawatt laser system into the existing Z-Backlighter laser facility. As part of this work, a short-pulse laser has been constructed to seed the larger Beamlet type Nd:phosphate glass slab amplifiers. This seed laser consists of an optical parametric chirped pulse amplification (OPCPA) system joined to a Nd:phosphate glass rod amplifier system in order to achieve multi-Joule sub-picosecond operation. The rod amplifier system has been modeled using the Miró code which shows good agreement with the experimental results. This system can achieve focal intensities up to 10¹⁸ W/cm² at a repetition rate of once every 20 min and has been applied to produce k-alpha X-rays in copper.     

1.57 times diffraction-limit high-energy laser based on a Nd:YAG slab amplifier and an adaptive optics system

In this Letter, a 116-actuator deformable mirror(DM) was used to correct the wavefront distortion in a 10.7 J,10 Hz neodymium-doped yttrium aluminum garnet(Nd:YAG) slab amplifier. By applying a pump-light homogenizer to transform the 3 × 1 near-field beam array into an integrated beam, the beam quality was greatly improved from 5.54 times diffraction limit(TDL) to 1.57 TDL after being corrected by the DM. To the best of our knowledge, this is the first investigation on beam quality control of an arrayed near-field beam in high-energy diode-pumped solid-state lasers.     

A laser amplifier model for system optimization

A laser amplifier system model has been developed, incorporating many of the features of real devices. The theoretical performance of systems with several amplifiers is investigated to illustrate the effects of optical filters and control techniques. Realistic and practical system limits are also identified.     

An injection-seeded high-repetition rate Ti:Sapphire laser for high-resolution spectroscopy and trace analysis of rare isotopes

An injection-seeded high-repetition rate (～10 kHz) Ti:sapphire laser with a spectral bandwidth of ～20 MHz and an average output power of above 1.5 W has been developed. We report on its demonstration and characteristics with respect to the spectral, temporal, and spatial properties as well as the output energy. In crossed-beam resonance ionization on a well-collimated thermal atomic beam, the ～200 MHz hyperfine structure of the D₂ transition at 308 nm of ²⁷Al has been well resolved. Applications of the system in the field of insource laser spectroscopy for on-line produced short-lived radioactive isotopes as well as for selective-trace isotope determination are discussed.     

用于高能啁啾脉冲压缩的光子晶体光栅的设计

为了克服目前高能短脉冲装置压缩光栅的损伤阈值无法满足要求的问题,针对星光Ⅲ装置皮秒激光束的压缩器,设计了由熔石英材料构成的、具有较高损伤阈值的光子晶体光栅,该光栅由2维光子晶体和表面光栅结构两部分组成,具有高反射效率和强角色散的能力。计算结果显示:经过优化设计的光子晶体光栅在波长1 053 nm,57°～77°的入射范围内,-1级衍射效率超过了92%,而当入射角为71°时,在1 040～1 090 nm光谱范围内,-1级衍射效率超过92%,性能满足使用要求。     

用于高能啁啾脉冲压缩的光子晶体光栅的设计

 为了克服目前高能短脉冲装置压缩光栅的损伤阈值无法满足要求的问题,针对星光Ⅲ装置皮秒激光束的压缩器,设计了由熔石英材料构成的、具有较高损伤阈值的光子晶体光栅,该光栅由2维光子晶体和表面光栅结构两部分组成,具有高反射效率和强角色散的能力。计算结果显示:经过优化设计的光子晶体光栅在波长1 053 nm,57°～77°的入射范围内,-1级衍射效率超过了92%,而当入射角为71°时,在1 040～1 090 nm光谱范围内,-1级衍射效率超过92%,性能满足使用要求。     

Performance of a dual-stage semiconductor laser amplifier for optical transmission repeater system

The performance of a dual-stage semiconductor laser amplifier consisting of a preamplifier and a power amplifier is evaluated theoretically and experimentally. The dual-stage optical amplifier can offer high-gain amplification with low noise figure by using a low-noise amplifier as a preamplifier. Using the dual-stage amplifier, 2.4 Gbits^–1 193 km optical fibre transmission was demonstrated. In addition, by applying an automatic power control system to the dual-stage amplifier, output power stabilization with wide dynamic range was obtained.     

Design and application of a laser beam alignment system based on the imaging properties of a multi-pass amplifier

Image relaying is presented as a technique for aligning beams onto mm-sized target of high power laser. On the basis of summarizing the preceeding work on the near-field image relaying of multiple spatial filters,the far-filed image relaying is suggested firstly. The near-field and far-field image relaying properties of multiple spatial filters in laser beams automatic alignment system are analyzed. A geometrical optics approach and an ABCD ray matrix theory are used throughout. The reasonable and optimum scheme for automatically aligning multi-pass beam paths is presented and demonstrated on the multi-pass amplifier system of the SG-Ⅲ prototype.     

基于铌酸锂双折射晶体的皮秒拍瓦激光系统光谱整形

为补偿皮秒拍瓦激光系统中钕玻璃宽带放大引起的增益窄化,提出了一种基于铌酸锂双折射晶体的高能量光谱整形方法.在相同强度调制下,对比了BBO、铌酸锂和石英3种晶体,针对1053 nm激光,选用了高双折射率、大口径且不易潮解的铌酸锂作为整形晶体.理论分析了晶体厚度、倾斜角、面内旋转角对强度调制的影响,发现它们分别决定调制的带宽、中心波长及深度.并对整形过程中晶体引入的光谱相位进行了分析,发现各阶色散量随晶体厚度、倾斜角、面内旋转角变化的规律,因此可通过上述参数控制各阶色散量.在此基础上,开展了中心波长为1053 nm、带宽为10 nm、调制深度为80%的光谱整形实验和相位测量实验,实验与理论分析相一致.针对神光Ⅱ皮秒拍瓦激光系统,利用上述整形方案,国内首次实现了1700 J, 6 nm (FWHM)的高能宽带激光输出,有效补偿了增益窄化.研究结果对国内基于钕玻璃放大系统的宽频带激光装置的工程研制具有重要意义.     

Design and application of a laser beam alignment system based on the imaging properties of a multi-pass amplifier

Image relaying is presented as a technique for aligning beams onto mm-sized target of high power laser. On the basis of summarizing the preceeding work on the near-field image relaying of multiple spatial filters, the far-filed image relaying is suggested firstly. The near-field and far-field image relaying properties of multiple spatial filters in laser beams automatic alignment system are analyzed. A geometrical optics approach and an ABCD ray matrix theory are used throughout. The reasonable and optimum scheme for automatically aligning multi-pass beam paths is presented and demonstrated on the multi-pass amplifier system of the SG-Ⅲprototype.     

A high-energy, chirped laser system for optical Stark deceleration

We describe a high-energy, frequency chirped laser system designed for optical Stark deceleration of cold molecules. This system produces two, pulse amplified beams of up to 700 mJ with flat-top temporal profiles, whose frequency and intensity can be well controlled for durations from 20 ns–10 μs. The two beams are created by amplifying a single, rapidly tunable Nd:YVO₄ microchip type laser at 1064 nm, which can be frequency chirped by up to 1 GHz over the duration of the pulse. Intensity modulation induced by relaxation oscillations in the microchip laser during the frequency chirp are virtually eliminated by injection locking a free running semiconductor diode laser before pulsed amplification.     

Generation of tunable subnanosecond laser pulses with a nitrogen laser pumped dye laser amplifier system

A simple method for generating single tunable subnanosecond dye laser pulses is described. A Rhodamin 6G dye laser is transversely pumped by a subnanosecond UV pulse of a TEA nitrogen laser. The narrowband output of the dye laser is amplified and shortened in a synchronously pumped amplifier. Narrowband pulses with a duration of 30–40 ps (fwhm) and a pulse power of 30 kW are obtained. They are tunable over the range of 580–600 nm.     

Plasma formation by high-repetition rate pulsed periodic laser irradiation of metals in air at atmospheric and reduced pressures

High-speed spectroscopy with spatial and temporal resolution is used to determine the basic plasma parameters and to examine the shift from an air plasma to an erosion plasma during multipulse laser irradiation of various metals at repetition rates ranging from 5 to 50 kHz with irradiances q > 2∙10⁸ W/cm². The formation of a distinctive surface plasma structure is observed which (a) facilitates the expulsion of the shielding layer of "air" plasma produced during the first of a series of laser pulses by vapor from the target and (b) inhibits the propagation of a metal vapor plasma front into the air during the subsequent pulses.     

Modeling of systems for broadening of spectrum of petawatt laser pulses and for their nonlinear compression

We numerically model the propagation of high-power laser pulses in a periodic system of nonlinear elements separated by spatial retransmitter filters. We show that, if the accumulated phase difference in an individual nonlinear element is restricted by a value smaller than 1.6 rad, it is possible to obtain the total accumulated phase difference greater than 14 rad while preserving the high radiation brightness. The considered scheme can be used for compressing superpower laser pulses.     

Fluence homogenization of a 240 J-diode-laser pump system for a multi-pass solid state laser amplifier

Within the POLARIS project multi-pass amplification to the 10 joule level for a femtosecond CPA laser system has been achieved by diode-pumping an Yb³⁺ doped fluoride-phosphate glass disk with a total energy of 240 J. The collimated light of 40 diode stacks is focussed onto a circular area of the glass disk with a diameter of 18 mm. A two-sided ring shaped setup is used for axially symmetric pumping. We developed a computer aided optimization routine for the positioning of single pump foci to gain a smooth homogeneously distributed, top-hat shaped pump profile. The homogeneity of the pump light distribution was improved substantially by this new method.PACS 42.55.Xi; 42.60.By; 42.60.Jf     

Ideal laser amplifier as a phase measuring system of a microscopic radiation field

A measuring system is described for the phase determination of a microscopic radiation field. The essential element of this system is a Q-switched Nd:YAG laser which serves as an ideal laser amplifier with a high amplification of approximately 10¹⁰, having insignificant quantum noise. The result for a phase measurement of several photons (about five) is presented.     

Sensitivity of a neodymium-glass laser amplifier

The results of an experimental study of the sensitivity of a neodymium-glass laser amplifier are presented. The sensitivity of a traveling wave laser amplifier is shown to be close to the theoretical limit, being 1.7 · 10^–6 W for a pass band of 6 · 10¹² cps.