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在飞秒激光与固体靶相互作用中,利用光学CCD相机和光学多道分析仪(OMA),分别在固体薄膜靶背表面法线方向测量了渡越辐射(TR)积分成像图案和渡越辐射光谱.测量结果显示,渡越辐射光斑呈现圆盘状结构,在圆盘中明亮而强的光信号呈局部化分布,并且有分离的光斑出现.该现象表明,超热电子在输运过程中存在成丝效应,引起严重的不稳定性;渡越辐射光谱在800 nm附近出现了尖峰,是基频波(ω0),并且光谱向红光方向移动;基频波产生的原因归结于超热电子束在传输过程中产生的微束团而引起的相干渡越辐射(CTR);光谱红移的原因是由于等离子体临界面的迅速膨胀所致;渡越辐射光强随靶厚度的增加而减小.
In the interaction between femtosecond laser and solid target, the transition radiation (TR) integral imaging pattern and transitional radiation were measured in the normal direction of the target surface of the solid film using an optical CCD camera and an optical multichannel analyzer (OMA) Spectrum.The results show that the transitional radiation spot presents a disc-like structure, the bright and strong optical signals in the disc are localized and the separated spots appear.The phenomenon shows that the superheated electrons are transported in the process of transport There is a filament-forming effect, causing serious instability; transition radiation spectrum peaked at 800 nm, is the fundamental frequency wave (ω0), and the spectrum to red light direction; Fundamental wave generation due to the superheat Due to the rapid expansion of the plasma interface; the intensity of the transition radiation increases with the increase of the target thickness Decrease