Demonstration of joule-level chirped pulse amplification based on tiled Ti:sapphire amplifier

A novel tiled Ti:sapphire(Ti:S)amplifier was experimentally demonstrated with>1 J amplified chirped pulse output.Two Ti:S crystals having dimensions of 14 mm×14 mm×25 mm were tiled as the gain medium in a four-pass amplifier.Maximum output energy of 1.18 J was obtained with 2.75 J pump energy.The energy conversion efficiency of the tiled Ti:S amplifier was comparable with a single Ti:S amplifier.The laser pulse having the maximum peak power of 28 TW was obtained after the compressor.Moreover,the influence of the beam gap on the far field was discussed.This novel tiled Ti:S amplifier technique can provide a potential way for 100 PW or EW lasers in the future.     

基于交叉偏振波产生的脉冲净化技术研究与应用

本文利用交叉偏振波产生技术(XPW)对800 nm波段钛宝石飞秒激光器输出的激光脉冲进行时域净化, 提高脉冲时域对比度, 并测量验证了10¹¹对比度的脉冲, 达到测量仪器的动态范围极限, 比初始脉冲时域对比度有三个量级的提高, XPW的效率为22%. 同时发现净化后脉冲光谱宽度也得到一定展宽, 进一步利用啁啾镜对和补偿片对净化后的脉冲进行色散补偿, 得到25 fs脉宽的脉冲. 利用该净化后的激光脉冲作为种子注入已有的太瓦级钛宝石啁啾脉冲放大系统中, 在输出脉冲能量250 mJ, 宽度50 fs, 对应峰值功率5 TW的情况下, 在主脉冲前100 ps以外的范围内测量验证了10¹¹的脉冲对比度.     

Wavefront correction of Ti:sapphire terawatt laser with varying precision of phase conjugation between deformable mirror and wavefront sensor

The phase conjugation between the deformable mirror and the wavefront sensor in the aberration correction of a terawatt Ti:sapphire laser is studied experimentally and theoretically in this paper. At varying values of phase-conjugation precision, we focus the corresponding beams into spots of the same size of 5.1 μm×5.3 μm with a f/4 parabola in the 32 TW/36 fs Ti:sapphire laser system. The results show that the precision of conjugation can induce an intensity modulation but does not significantly affect the wavefront correction.     

Experimental investigation on pulse-contrast degradation caused by surface reflection in optical parametric chirped-pulse amplification

In this Letter, we experimentally explore the pulse-contrast degradation caused by surface reflection in optical parameter chirped-pulse amplification. Different pump-to-signal conversion efficiencies and post-pulses with different intensities are obtained by changing the seed-pulse or pump-pulse energy and inserting etalons with different reflection coefficients, respectively. The contrast measurements show that the generated first pre-pulse intensity is proportional to the product of the surface reflection intensity ratio and the square of the pump-to-signal conversion efficiency.     

Improvement of the large aperture Ti：sapphire amplifiers in the petawatt femtosecond laser system at SIOM

We report the recent improvement on the petawatt (PW) femtosecond Ti:sapphire chirped pulse amplification (CPA) laser system at Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences. By enlarging the sizes of the pump and signal beams in the large aperture Ti:sapphire amplifiers and optimizing the whole laser system, the output laser energy before the pulse compressor is upgraded to 42.6 J. Accordingly, the peak power of the laser system exceeds 1 PW. The shot-to-shot instability of the output laser energy at about 40 J is less than ±5%.     

Experimental study of K-shell X-ray emission generated from nanowire target irradiated by relativistic laser pulses

K-shell X-ray emission from a Cu nanowire target irradiated by an ultraintense femtosecond laser pulse is studied using an elliptically bent quartz crystal and imaging plate. The designed bent crystal spectrometer has better spectral resolution, which is higher than 1 000. The absolute Kα radiation photon yields are obtained from the experimental results and the Monte-Carlo model. The conversion efficiency of the Cu Kα line is estimated to be 0.019% from the interaction of 4 J, 50-fs laser pulse irradiated on a Cu nanowire target. The high yield of K shell X-ray has important applications in X-ray emission source.     

Wavefront correction of Ti： sapphire terawatt laser with varying precision of phase conjugation between deformable mirror and wavefront sensor

The phase conjugation between the deformable mirror and the wavefront sensor in the aberration correction of a terawatt Ti:sapphire laser is studied experimentally and theoretically in this paper.At varying values of phaseconjugation precision,we focus the corresponding beams into spots of the same size of 5.1 μm× 5.3 μm with a f/4 parabola in the 32 TW/36 fs Ti:sapphire laser system.The results show that the precision of conjugation can induce an intensity modulation but does not significantly affect the wavefront correction.     

Wavefront Correction of Pettawat Laser System by a Deformable Mirror with 50mm Active Aperture

We firstly propose and demonstrate a new economical approach that can correct the wavefront of the petwatt Ti：sapphire laser system with a beam size of 150mm. By using a deformable mirror with 50mm active aperture in the end of the laser, the focal spot size is reduced effectively. The experimental results show that the new approach is simple, less-expensive and valid from a technical and economical point. This technique could be applied to correct the wavefront of a large optical beam with a smaller aperture deformable mirror.     

Generation of 17-TW 23-fs Pulses with a Two-Stage Ti：Sapphire Amplifier at Repetition Rate 10 Hz

We have developed a two-stage Ti：sapphire amplifier system which can produce 17- TW/23-fs pulses at a repetition rate 10Hz. A birefringent plate is used in the regenerative amplifier to alleviate gain narrowing, while an all- reflective cylindrical-mirror-based pulse stretcher and an acousto-optic programmable dispersive filter （AOPDF） are used to compensate for the higher order dispersion of the system.