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研究了周期量级的圆偏振激光在空气中成丝产生太赫兹辐射的偏振特性。将中心波长1.8μm、脉宽8.6fs的圆偏振红外激光脉冲聚焦到空气中,形成等离子体细丝,产生太赫兹辐射。通过测量太赫兹辐射的偏振状态,和偏振方向与驱动激光载波-包络相位的关系,发展太赫兹波偏振控制的方法。实验结果表明,太赫兹辐射为椭圆偏振,而且偏振平面随着驱动激光载波-包络相位的变化而转动。这对太赫兹波的偏振控制有重要意义,并为周期量级激光载波-包络相位的测量提供了新方法。
The polarization characteristics of terahertz radiation generated by the circularly polarized laser beam in air are studied. The center wavelength of 1.8μm, pulse width 8.6fs circularly polarized infrared laser pulse focused into the air, the formation of plasma filaments, resulting in terahertz radiation. The method of developing terahertz wave polarization control is developed by measuring the polarization state of terahertz radiation and the relationship between the polarization direction and the carrier-envelope phase of driving laser. Experimental results show that the terahertz radiation is elliptically polarized, and the plane of polarization rotates as the carrier phase of the driving laser changes. This is of great significance to the control of the terahertz wave polarization and provides a new method for the measurement of periodic laser carrier-envelope phase.