Two color laser pulses are used to form an air plasma and generate broadband infrared radiation suitable as a seed for backward Raman amplification of CO₂ laser pulses. Broadband radiation in the atmospheric window from 8 to 14 μm is observed. The infrared radiation is characterized using a long wavelength grating spectrometer specially designed to accept an ionizing laser filament at its input plane. The long wavelength infrared yield is greatly enhanced by chirping the drive pulse, but this affects the spectrum as well. Unidirectional pulse propagation simulations suggest that this is due in part to the dependence of the nonlinear refractive index on the pulse duration.

中文翻译：

---

在长波长红外中进行等离子体压缩的种子源

使用两种颜色的激光脉冲来形成空气等离子体，并生成宽带红外辐射，该辐射适合作为向后拉曼放大CO ₂激光脉冲的种子。宽带在从8至14的大气窗口辐射μ m的观察。红外辐射使用专门设计为在其输入平面接受电离激光灯丝的长波长光栅光谱仪进行表征。通过chi声驱动脉冲可以大大提高长波长的红外产量，但这也会影响光谱。单向脉冲传播模拟表明，这部分归因于非线性折射率对脉冲持续时间的依赖性。