Abstract：Nanosecond laser-induced air plasma has a wide spectrum of radiation from ultraviolet, visible, near-infrared, and even radio frequency microwaves, but most people are currently concerned about spectral radiation from the ultraviolet to visible wavelength range. Laser plasma has many advantages as a new type of infrared radiation source. Compared with infrared bombs and infrared interference means, air plasma infrared radiation sources can be flexibly arranged and have low cost. Therefore, the study of the infrared radiation characteristics of air plasma is necessary. In view of the current research on the infrared interference of pulsed laser-induced air plasma, the infrared radiation characteristics of nanosecond pulsed laser-induced air plasma with a laser wavelength of 532 nm are experimentally studied. The influences of laser energy on the infrared radiation intensity of the air plasma are discussed, the angle distribution characteristics of the infrared radiation are presented, the possible mechanisms of plasma infrared radiation are analyzed. The experimental results show that the infrared spectrum of the laser-induced air plasma in the range of 950～1 700 nm is a superposition of the line spectrum and the continuous spectrum. The main spectrum is the neutral atomic lines of nitrogen and oxygen, and the infrared radiation of nitrogen atom dominates at the whole radiation. As the laser pulse energy increases, which induces the amount of oxygen and nitrogen atoms increasing produced by the air breakdown, the intensity of the infrared spectrum of the air plasma gradually increases. With the change of infrared radiation detection angle, the spectral intensity of OⅠ 1 128.63 nm and NⅠ 1 246.96 nm and 1 362.42 nm reaches the maximum at the detection angle of 75 degrees. When the detection angle is 120 degrees, the spectral intensity of NⅠ 1 011.46 nm and 1 053.96 nm reaches peak. The biggest reason is that the intensity of infrared radiation in the air plasma shows a spatial asymmetry with the change of the detection angle, indicating that the spatial distribution of different particles in the air plasma is asymmetric.
Key words：Nanosecond pulsed laser; Air plasma; Infrared radiation
王兴生，苑莉薪，李 馨，王 铭，高 勋, 林景全. 纳秒激光诱导空气等离子体的红外辐射特性研究[J]. 光谱学与光谱分析, 2019, 39(09): 2698-2701.
WANG Xing-sheng, YUAN Li-xin, LI Xin, WANG Ming, GAO Xun, LIN Jing-quan. The IR Radiation Characteristics of Nanosecond Pulsed Laser Induced Air Plasma. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(09): 2698-2701.
