基于光放大的长脉冲抽运太赫兹激光

为了获得较窄增益带宽、较大光强的太赫兹辐射，尝试了利用TEA CO₂激光器对6 W可调谐连续波CO₂种子激光实行双程光放大实验，以期望获得长脉冲、高峰值功率的抽运光.通过实验，获得了大约30倍的放大系数，放大光输出功率随种子光注入功率的增加而增加，其中10 P （20）支线表现更加突出，并且被放大的激光支线半峰全宽在14 μs左右.基于这种长脉冲抽运源，建立了一种产生脉冲太赫兹的动力学模型，给出了产生太赫兹辐射的饱和抽运光强表达式，确定了抽运光的光强范围.另外， 关键词： 激光物理 长脉冲 动力学模型 太赫兹激光

Long-pulse optical pumping THz laser based on optical amplification

To obtain narrower linewidth and more intense THz radiation, long-pulse and high-peak power optical pumping source is attempted by performing a light amplification experiment in which a 6 W tunable continuous-wave CO₂ seeding laser is amplified by a double-pass amplifier with TEA CO₂ laser. The result of an amplification factor of 30 at 14 μs pulse duration （FWHM） is obtained experimentally. During the amplification, the output power of the amplified light increases with that of seeding light increasing, especially for the CO₂ 10P （20）line. Based on the optical pumping source of long pulse laser, a dynamic model for generating pulsed THz radiation is established, and the expression of saturation pumping intensity which yields THz radiation is given, thus the range of pumping intensity can be determined. In addition, by solving time-dependent equation of dynamic model, the expression of pumping energy absorbed by THz medium is deduced. Theoretical analysis shows further that the heavy molecules will be more appropriate for THz gain medium for long pulse pumping source, and no THz radiation can be generated due to the absence of population reversion below pumping intensity.