雙脈沖飛秒激光誘導(dǎo)擊穿光譜研究
發(fā)布時(shí)間：2018-12-24 12:39
【摘要】：激光誘導(dǎo)擊穿光譜技術(shù)(Laser-induced breakdown spectroscopy,LIBS)是當(dāng)今材料分析領(lǐng)域的一個(gè)研究熱點(diǎn)。由于飛秒激光(femtosecond laser,fs laser)脈沖的超短持續(xù)時(shí)間,超高峰值功率,以及極低的熱效應(yīng),采用飛秒激光作為光源來研究材料的誘導(dǎo)擊穿光譜可以提高探測的空間分辨率,減少樣品材料的去除量,實(shí)現(xiàn)超遠(yuǎn)距離探測等。然而相對(duì)納秒激光,飛秒激光產(chǎn)生的等離子體的信號(hào)強(qiáng)度較弱,如何提高飛秒激光誘導(dǎo)擊穿光譜(fs-LIBS)的信號(hào)強(qiáng)度是一個(gè)迫切需要解決的問題。采用共線雙脈沖取代單脈沖可以有效提高飛秒激光誘導(dǎo)擊穿光譜的信號(hào)強(qiáng)度。然而,雙脈沖飛秒激光誘導(dǎo)擊穿光譜的增強(qiáng)機(jī)理研究仍然充滿爭議或有待研究�；谶@一背景,本文系統(tǒng)地研究了金屬、半導(dǎo)體、有機(jī)電介質(zhì)、以及火焰等不同物質(zhì)的雙脈沖飛秒激光誘導(dǎo)擊穿光譜的信號(hào)隨雙脈沖延時(shí)的變化規(guī)律,通過飛秒激光與不同物質(zhì)相互作用的機(jī)理深入探討了雙脈沖飛秒激光信號(hào)的增強(qiáng)機(jī)制。本論文研究工作的創(chuàng)新點(diǎn)概括如下:(1)通過研究金屬材料銅的雙脈沖fs-LIBS信號(hào),發(fā)現(xiàn)導(dǎo)致信號(hào)增強(qiáng)的原因是第二個(gè)脈沖對(duì)第一個(gè)脈沖產(chǎn)生的等離子體羽輝的加熱作用,使得等離子體進(jìn)一步離化升溫,壽命延長,從而使得探測光譜的信號(hào)增強(qiáng)。同時(shí)發(fā)現(xiàn)在較小的激光通量下的雙脈沖fs-LIBS信號(hào)的增強(qiáng)倍數(shù)較高,且在1 ps內(nèi)飛秒激光的脈沖寬度的變化對(duì)雙脈沖fsLIBS沒有影響。(2)通過對(duì)比半導(dǎo)體材料硅的雙脈沖fs-LIBS信號(hào)與其燒蝕坑的表面形貌和燒蝕深度,揭示了造成硅的雙脈沖fs-LIBS信號(hào)增強(qiáng)的主要原因是雙脈沖飛秒激光的材料去除量大于單脈沖的材料去除量。(3)首次研究了有機(jī)電介質(zhì)材料PMMA(聚甲基丙烯酸甲酯,俗稱有機(jī)玻璃)的雙脈沖fs-LIBS。發(fā)現(xiàn)其等離子體中的各粒子的信號(hào)增強(qiáng)倍數(shù)從大到小依次為離子、中性原子、分子。盡管其等離子體的動(dòng)態(tài)變化過程受到周圍空氣影響,但是通過對(duì)電子密度和等離子體溫度的研究發(fā)現(xiàn)造成其信號(hào)增強(qiáng)的主要機(jī)制與金屬材料類似,也是第二個(gè)飛秒激光脈沖對(duì)第一個(gè)脈沖產(chǎn)生的等離子體羽輝的加熱作用。(4)首次將雙脈沖fs-LIBS用于火焰燃燒的研究。由于飛秒激光誘導(dǎo)產(chǎn)生的氧炔焰中CN信號(hào)與火焰的燃氧比成正比,說明fs-LIBS的CN光譜可以用來探測火焰的燃氧比。通過使用雙脈沖fs-LIBS,CN光譜的信號(hào)強(qiáng)度得到了較大的增強(qiáng),使得用雙脈沖fs-LIBS探測火焰燃氧比的靈敏度提高。
[Abstract]:Laser induced breakdown spectroscopy (Laser-induced breakdown spectroscopy,LIBS) is a hot topic in the field of material analysis. Because of the ultrashort duration of femtosecond laser (femtosecond laser,fs laser) pulse, ultra-high peak power, and extremely low thermal effect, using femtosecond laser as a light source to study the induced breakdown spectrum of materials can improve the spatial resolution of the detection. To reduce the sample material removal amount, to achieve ultra-long-distance detection and so on. However, compared with nanosecond laser, the signal intensity of plasma produced by femtosecond laser is relatively weak. How to improve the signal intensity of femtosecond laser induced breakdown spectroscopy (fs-LIBS) is an urgent problem to be solved. The signal intensity of femtosecond laser induced breakdown spectrum can be improved by using collinear double pulse instead of single pulse. However, the enhancement mechanism of double pulse femtosecond laser induced breakdown spectroscopy is still controversial. Based on this background, the variation of the double pulse femtosecond laser induced breakdown spectra of metals, semiconductors, organic dielectrics, flame and other materials with double pulse delay is systematically studied in this paper. The enhancement mechanism of double pulse femtosecond laser signal is discussed through the interaction mechanism between femtosecond laser and different matter. The innovations of this thesis are summarized as follows: (1) by studying the double pulse fs-LIBS signal of copper, it is found that the cause of the signal enhancement is the heating effect of the second pulse on the plasma plume produced by the first pulse. The plasma is further ionized and the lifetime is prolonged, which enhances the signal of the detection spectrum. At the same time, it is found that the enhancement times of dual-pulse fs-LIBS signal are higher at low laser flux. The pulse width of femtosecond laser has no effect on the double pulse fsLIBS within 1 ps. (2) by comparing the double pulse fs-LIBS signal of the semiconductor silicon with the surface morphology and ablation depth of the ablation pit, It is revealed that the main reason for the enhancement of double pulse fs-LIBS signal of silicon is that the material removal of double pulse femtosecond laser is larger than that of single pulse. (3) the organic dielectric material PMMA (polymethyl methacrylate) is studied for the first time. Double pulse fs-LIBS. (commonly known as plexiglass) It is found that the signal enhancement times of each particle in the plasma are ion, neutral atom and molecule in order from large to small. Although the dynamic process of the plasma is influenced by the ambient air, it is found that the main mechanism of the signal enhancement is similar to that of the metal material through the study of the electron density and the temperature of the plasma. It is also the second femtosecond laser pulse to heat the plasma plume produced by the first pulse. (4) the double pulse fs-LIBS is used for flame combustion for the first time. Because the CN signal produced by femtosecond laser induced oxyacetylene flame is proportional to the ratio of combustion to oxygen, the CN spectrum of fs-LIBS can be used to detect the ratio of combustion to oxygen. The signal intensity of double pulse fs-LIBS,CN spectrum is greatly enhanced, which makes the sensitivity of detecting flame fuel to oxygen ratio improved by using double pulse fs-LIBS.
【學(xué)位授予單位】：北京理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB302.5
[Abstract]:Laser induced breakdown spectroscopy (Laser-induced breakdown spectroscopy,LIBS) is a hot topic in the field of material analysis. Because of the ultrashort duration of femtosecond laser (femtosecond laser,fs laser) pulse, ultra-high peak power, and extremely low thermal effect, using femtosecond laser as a light source to study the induced breakdown spectrum of materials can improve the spatial resolution of the detection. To reduce the sample material removal amount, to achieve ultra-long-distance detection and so on. However, compared with nanosecond laser, the signal intensity of plasma produced by femtosecond laser is relatively weak. How to improve the signal intensity of femtosecond laser induced breakdown spectroscopy (fs-LIBS) is an urgent problem to be solved. The signal intensity of femtosecond laser induced breakdown spectrum can be improved by using collinear double pulse instead of single pulse. However, the enhancement mechanism of double pulse femtosecond laser induced breakdown spectroscopy is still controversial. Based on this background, the variation of the double pulse femtosecond laser induced breakdown spectra of metals, semiconductors, organic dielectrics, flame and other materials with double pulse delay is systematically studied in this paper. The enhancement mechanism of double pulse femtosecond laser signal is discussed through the interaction mechanism between femtosecond laser and different matter. The innovations of this thesis are summarized as follows: (1) by studying the double pulse fs-LIBS signal of copper, it is found that the cause of the signal enhancement is the heating effect of the second pulse on the plasma plume produced by the first pulse. The plasma is further ionized and the lifetime is prolonged, which enhances the signal of the detection spectrum. At the same time, it is found that the enhancement times of dual-pulse fs-LIBS signal are higher at low laser flux. The pulse width of femtosecond laser has no effect on the double pulse fsLIBS within 1 ps. (2) by comparing the double pulse fs-LIBS signal of the semiconductor silicon with the surface morphology and ablation depth of the ablation pit, It is revealed that the main reason for the enhancement of double pulse fs-LIBS signal of silicon is that the material removal of double pulse femtosecond laser is larger than that of single pulse. (3) the organic dielectric material PMMA (polymethyl methacrylate) is studied for the first time. Double pulse fs-LIBS. (commonly known as plexiglass) It is found that the signal enhancement times of each particle in the plasma are ion, neutral atom and molecule in order from large to small. Although the dynamic process of the plasma is influenced by the ambient air, it is found that the main mechanism of the signal enhancement is similar to that of the metal material through the study of the electron density and the temperature of the plasma. It is also the second femtosecond laser pulse to heat the plasma plume produced by the first pulse. (4) the double pulse fs-LIBS is used for flame combustion for the first time. Because the CN signal produced by femtosecond laser induced oxyacetylene flame is proportional to the ratio of combustion to oxygen, the CN spectrum of fs-LIBS can be used to detect the ratio of combustion to oxygen. The signal intensity of double pulse fs-LIBS,CN spectrum is greatly enhanced, which makes the sensitivity of detecting flame fuel to oxygen ratio improved by using double pulse fs-LIBS.
【學(xué)位授予單位】：北京理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB302.5
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