Novel Laser Energy Gain Media Capable of 100-Thousand-Time Amplification
A pulse with width comparable to that of the oscillator, yet with 105-106 times the energy, can be obtained with Yb:SSO CPA amplifier system.
Researchers in Prof. Xiaoyan Liang's group, from Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, have conducted series of experiments on the CW and CWML oscillators based on Yb:SSO, and for the first time to the best of our knowledge, applied this crystal into the chirped pulse amplifier (CPA) to explore its potential as good amplification medium. Eventually, a pulse with width comparable to that of the oscillator, yet with 105-106 times the energy, was obtained. It is reported in Chinese Optics Letters Vol.13, No.1 (2015).
Yb-doped silicate Yb3+:Sc2SiO5 (Yb:SSO) has some excellent crystalline features such as broad gain bandwidth, high emission cross sections and thermal conductivity. These features indicate a potential use of Yb:SSO in the development of high average power continuous wave (CW) and ultrafast continuous wave mode-locked (CWML) lasers. A number of studies have been reported on Yb:SSO oscillators, including CW and CWML operation, over the last few years. Nevertheless, its capability of energy amplification has not been investigated.
In the study, a self-made femtosecond oscillator is used as the seed source. And a single chirped volume bragg grating (CVBG), with simpler structure and easier alignment compared with traditional grating, is used as both stretcher and compressor, which makes the whole system more compact.
Researchers from Prof. Liang's group believe that the result of this study confirms that Yb:SSO has great potential as CPA medium. Regenerative amplifiers based on this material could have important application in industry, medical and scientific areas such as micro-machining, biological imaging, microsurgery and nonlinear spectroscopy.
In the future work, effective measures need to be taken to suppress the gain narrowing effect in CPA, so that output pulses with shorter duration can be obtained. Moreover, in this way, a variety of insertion loss can be effectively attenuated to improve the amplification efficiency.
掺镱硅酸钪用于啁啾脉冲放大实现十万倍能量增益
通过Yb:SSO CPA放大系统能够获得宽度可与振荡器比拟、而能量提高了105-106倍的激光脉冲。
在材料微细加工、粒子加速等领域，通常要求激光具有很高的功率或能量。仅靠激光振荡器来获取高功率或高能量激光通常比较困难。激光振荡器一般在小能量状态工作，然后再经放大器得到大能量、高质量的激光输出。
中国科学院上海光学精密机械研究所的梁晓燕研究员课题组首次将掺镱硅酸钪（Yb:SSO）用于啁啾脉冲放大器（CPA），将脉冲能量由纳焦量级放大为数百微焦量级。相关研究成果发表在Chinese Optics Letters 2015年第1期上。
掺镱硅酸钪具有良好的晶体特性，例如增益带宽宽、发射截面大、热导性高等，因此非常适合于产生超快高功率激光。然而，对它能量放大特性的研究鲜有报道。
该实验采用自搭建的飞秒激光振荡器作为种子源；以单块啁啾布拉格体光栅同时作为放大前种子脉冲的展宽器和放大后脉冲的压缩器。
课题组的研究人员认为，实验结果证明Yb:SSO是一种非常有潜力的CPA放大介质；基于该种晶体的CPA可以在材料精细微加工、生物成像、显微外科手术、非线性光谱学等工业、医疗和科学领域具有重要的应用。
后续工作将主要采取有效措施抑制该CPA中的增益窄化效应，从而获得更窄的输出脉冲宽度，以及有效地减小各种插入损耗，提高其放大效率。