中文摘要：

对强飞秒激光聚焦在空气中所激发的等离子体的发射光谱进行了实验研究.结果表明,光谱特征表现为短波段（截至波长为340nm）强烈的连续谱和长波段（波长在800nm附近）强度相对较低的线光谱.在脉冲宽度（50fs）保持不变而不断调节激光脉冲能量时,等离子体光谱形状的特征基本相似;当激光脉冲能量（1mJ）保持不变而脉冲宽度从50fs增加至500fs和1ps时,连续谱的峰值（500nm）显得格外突出,并开始呈现出线光谱特征.

英文摘要：

The emission spectra produced in ambient air with focused strong femtosecond laser pulses are studied experimentally.The results show the emission spectrum presents the short-wavelength continuum spectrum with stronger intensity（cutoff wavelength 340 nm） and long-wavelength line spectrum with less weak intensity（near 800 nm）.A similar spectrum shape can be acquired with fixed pulse width 50 fs and adjustable laser pulse energy.When the pulse energy is 1 mJ and the pulse width increases from 50 fs to 1ps,the peak value of continuum spectrum located in 500 nm wavelength becomes strong and gradually presents the line spectrum characteristics.