PMMA材料在线偏振和圆偏振光下的超连续光谱特性分析

飞秒激光在透明材料加工过程中会出现超连续光谱现象。在阐述超连续光谱产生的原理的基础上，为了分析PMMA材料在不同偏振光下产生的超连续光谱的阈值，设计了线偏光和圆偏光及不同能量加工PMMA材料的实验方案。利用光谱仪对产生的超连续光谱信号进行采集及处理，分析出不同能量下的线偏振(TE和TM)和圆偏振两种偏振态的超连续光谱的变化规律，并对比了相同能量下线偏振和圆偏振的超连续光谱的区别。实验中采用脉宽160 fs、中心波长为775 nm的飞秒激光，实验结果表明，同一偏振下能量越大，光谱谱宽越宽；通过对比不同能量下的光谱特性，观测出产生超连续光谱的阈值, 线偏振光的阈值为0.46 μJ，圆偏振光的阈值为0.586 μJ；对比相同能量下的线偏振和圆偏振光，线偏振的谱宽比圆偏振的宽。

Analysis of supercontinuum spectra characteristics of PMMA materials in linear polarization and circularly polarized light

Super continuous spectrum phenomenon can appear when using femtosecond laser in the process of transparent materials.On the basis of the principle of supercontinuum generation, the experimental scheme of linear polarization and circular polarization and PMMA materials with different energies is designed in order to analyze the threshold of supercontinuum spectrum of PMMA material under different polarized lights.Supercontinuum spectra of two polarized states of linear polarization (TE and TM) and circular polarization under different energies are analyzed and compared with superconducting spectra of the same energy. In the experiment, femtosecond laser with the pulse width of 160 fs and center wavelength of 775 nm is used. Experimental results show that energy of the same polarization is wider and spectrum width is wider. By comparing spectral characteristics under different energies, threshold of the spectrum and the circularly polarized light is 0.46 μJ and 0.586 μJ respectively. The spectral width of the linear polarization is wider than that of the circular polarization and circularly polarized light.