物理学报2017，Vol.66Issue(4)：50-55,6.DOI:10.7498/aps.66.040601
色散对双晶交叉偏振滤波输出特性的影响
Influences of quadratic spectral phase on characteristics of two crystal cross-polarized generation with femtosecond pulses
摘要
Abstract
The rapid developments of ultra-intense and ultra-short laser offer the possibility to study laser driven ion accel-eration with using solid density target. However, the prepulse and amplified spontaneous emission generated in the amplification can create preplasma at the target front by heating, melting and evaporating a portion of a solid density. The main pulse then interacts with the preplasma, which would be harmful to laser ion acceleration. Therefore, many methodshavebeendevelopedtoenhancethetemporalcontrastofhighpowerlasersystem,suchassaturable absorber, cross polarized wave generation (XPW) and plasma mirror. With many advantages, such as high conversion efficiency, introducing neither spatial nor spectral distortions, and easy setup compared with other mechanisms, XPW has been used to clean the femtosecond laser system. Besides that, the spectrum of the XPW pulse could be broadened by √3 times under the best condition compared with the initial spectrum. It can solve the spectrum narrowing problem during the laser amplification to obtain ultra-short femtosecond laser pulse. Here, we experimentally investigate the output power, spectrum bandwidth and center wavelength shift of the generated cross-polarized wave according to the input pulse quadratic spectral phase. The femtosecond laser pulse in compact laser plasma accelerator system at Peking University is used to investigate the role of quadratic spectral phase in characterizing the two crystal cross-polarized generation. The Ti: Sapphire-based laser system has a central wavelength of 798 nm and bandwidth of 35.5 nm which allows the pulse to be compressed down to 40 fs duration (FWHM). Typical the input pulse energy of XPW is 150 μJ and the laser system operates well at 1 kHz repetition rate. The quadratic spectral phase can be increased by changing the position of compressor grating. The conversion efficiency, spectrum bandwidth and the central wavelength shift by changing the quadratic spectral phase are measured. The conversion efficiency is 17%when quadratic spectral phaseφ2=0, and decreases as quadratic spectral phase increases. The rapid decrease is caused by negative quadratic spectral phase. The spectrum bandwidth is 62 nm under the optimum condition, and the broadening effect exists when quadratic spectral phase is in a range of?280 fs2 <φ2 <1400 fs2. It is slowly blue-shifted when φ2 >0 and stays at 772 nm when φ2 >1000 fs2. It starts to be red-shifted whenφ2<0 and stays at 806 nm finally. In conclusion, with the increase of quadratic spectral phase, we observe the effects of conversion efficiency and spectrum bandwidth and the shift of central wavelength. Moreover, the influences of positive and negative quadratic spectral phase on characteristics of XPW are different. Our result shows that the negative quadratic spectral phaseis more effective at reducing the conversion efficiency and spectrum bandwidth than the positive one.关键词
啁啾脉冲放大/交叉偏振滤波/光谱/色散Key words
chirp pulse amplification/cross-polarized generation/spectrum/quadratic spectral phase引用本文复制引用
耿易星,李荣凤,赵研英,王大辉,卢海洋,颜学庆..色散对双晶交叉偏振滤波输出特性的影响[J].物理学报,2017,66(4):50-55,6.基金项目
Project supported by the National Natural Science Foundation of China (Grant No. 11504009) and the National Grand Instrument Project, China (Grant No. 2012YQ030142). 国家自然科学基金(批准号: 11504009)和国家重大科学仪器设备开发专项(专项号:2012YQ030142)资助的课题. （Grant No. 11504009）
