緊聚焦條件下飛秒激光產(chǎn)生空氣等離子體的動(dòng)態(tài)演化特性
本文選題:激光光學(xué) 切入點(diǎn):飛秒激光傳輸 出處:《中國(guó)激光》2017年07期 論文類型:期刊論文
【摘要】:采用具有旋轉(zhuǎn)對(duì)稱性的三維空間電離模型,對(duì)緊聚焦條件下中心波長(zhǎng)為800nm、脈沖寬度為50fs的激光脈沖產(chǎn)生的空氣等離子體的時(shí)間和空間特性進(jìn)行了數(shù)值模擬,揭示了整個(gè)等離子體區(qū)折射率的動(dòng)態(tài)演化過(guò)程。計(jì)算結(jié)果表明:當(dāng)激光脈沖開(kāi)始聚焦時(shí),靠近焦點(diǎn)前方的空氣首先被電離,隨后產(chǎn)生一個(gè)中心區(qū)域達(dá)到飽和、邊緣具有很高折射率梯度的水滴狀等離子區(qū)域;隨著激光脈沖繼續(xù)向焦點(diǎn)傳播并越過(guò)焦點(diǎn),等離子體區(qū)進(jìn)一步向前延伸,直至在焦點(diǎn)前后形成一個(gè)近乎對(duì)稱的雙卵形結(jié)構(gòu);脈沖通過(guò)焦點(diǎn)區(qū)域后,空氣等離子體強(qiáng)度沿傳播方向逐漸減弱,直到最終完全消失;在10倍物鏡聚焦下,脈沖能量為500μJ、脈沖寬度為50fs的激光脈沖產(chǎn)生的空氣等離子體由產(chǎn)生到消失的整個(gè)過(guò)程約持續(xù)3ps。理論計(jì)算結(jié)果與30kPa低氣壓環(huán)境下的實(shí)驗(yàn)觀測(cè)結(jié)果相吻合。
[Abstract]:Using a three-dimensional spatial ionization model with rotational symmetry, the temporal and spatial characteristics of air plasma produced by a laser pulse with a central wavelength of 800 nm and a pulse width of 50 fs are numerically simulated under the condition of compact focusing. The dynamic evolution of refractive index in the whole plasma region is revealed. The calculated results show that when the laser pulse begins to focus, the air near the focal point is first ionized and then a central region is saturated. As the laser pulse continues to propagate to the focal point and crosses the focus, the plasma region further extends forward until a nearly symmetrical double oval structure is formed before and after the focal point. After the pulse passes through the focal area, the intensity of the air plasma decreases gradually along the direction of propagation, and finally disappears completely. The pulse energy is 500 渭 J and the pulse width is 50 fs. The whole process from generation to disappearance of the air plasma lasts about 3 ps.The theoretical calculation results are in agreement with the experimental results at 30 KPA low pressure.
【作者單位】: 南開(kāi)大學(xué)現(xiàn)代光學(xué)研究所光學(xué)信息技術(shù)科學(xué)教育部重點(diǎn)實(shí)驗(yàn)室;
【基金】:國(guó)家自然科學(xué)基金(11274185,61137001)
【分類號(hào)】:O437;O53
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