本文選題：太赫茲氣體光子學(xué)　切入點(diǎn)：光電流模型　出處：《華中科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：近年來,利用強(qiáng)場激光誘導(dǎo)氣體等離子體產(chǎn)生太赫茲輻射的研究吸引了眾多科研工作者的關(guān)注。與其他產(chǎn)生方法相比,該技術(shù)不用考慮介質(zhì)(氣體)的損耗,沒有聲子共振和吸收,得到的輻射場強(qiáng)度大、光譜范圍寬,并且可以利用其原理的逆過程來同時(shí)進(jìn)行探測。本論文基于當(dāng)前流行的光電流模型,圍繞如何獲得更高強(qiáng)度和可調(diào)制的太赫茲波輸出,從改變、調(diào)制光場成分以及加入恒定磁場等角度做了一系列的探索。論文首先描述了雙色場光電流模型的計(jì)算,作為后續(xù)研究的理論基礎(chǔ)。然后引入三倍頻光,并通過模擬計(jì)算研究了光束間相位差對輻射強(qiáng)度的影響。通過對特殊值點(diǎn)一個(gè)周期光場的具體分析,對三倍頻光導(dǎo)致輻射增強(qiáng)給出了一個(gè)簡單而又物理意義清晰的解釋。其次,從改變電子運(yùn)動的空間對稱性出發(fā),研究了加入恒定磁場帶來的影響。詳細(xì)推導(dǎo)了電子在光場和磁場雙重作用下速度的離散表達(dá)式,并給出了電磁輻射的計(jì)算方法。結(jié)果表明,加入磁場不但可以增強(qiáng)輻射,還能大大減小相位差的影響,獲得比較穩(wěn)定的輸出。最后,從減小光脈沖脈寬和引入線性啁啾兩個(gè)角度來改變單色光場,探究對低頻輻射的影響。啁啾會導(dǎo)致激光頻譜向高頻和低頻方向展寬,而周期量級飛秒激光波形本身就是不對稱的,這都會導(dǎo)致太赫茲輻射的增強(qiáng),并且這兩種作用的效果是累積的。另外研究還發(fā)現(xiàn),高頻方向的展寬會隨著啁啾參數(shù)的增大而增大,而低頻方向的展寬卻呈現(xiàn)一種間歇性起伏的變化趨勢。整篇論文通過理論研究發(fā)現(xiàn)了幾種增強(qiáng)太赫茲輻射的方法,并對結(jié)果給出了自己的解釋,為將來進(jìn)一步的理論和實(shí)驗(yàn)研究做了基礎(chǔ)。
[Abstract]:In recent years, the research on the generation of terahertz radiation from gas plasma induced by a strong field laser has attracted the attention of many researchers. Compared with other generation methods, this technique does not take into account the loss of medium (gas). Without phonon resonance and absorption, the radiation field is large, the spectral range is wide, and the inverse process of its principle can be used to simultaneously detect it. A series of explorations are made on how to obtain higher intensity and modulable terahertz wave output from the angles of changing, modulating the composition of the light field and adding a constant magnetic field. Firstly, the calculation of the photocurrent model of the two-color field is described. As the theoretical basis for further study, the third harmonic light is introduced, and the influence of phase difference between beams on the radiation intensity is studied by simulation. The specific analysis of a periodic light field at a special value point is given. This paper gives a simple and clear explanation of the radiation enhancement caused by triple-frequency light. Secondly, starting from changing the spatial symmetry of electron motion, The influence of the constant magnetic field is studied. The discrete expression of electron velocity under the action of light field and magnetic field is derived in detail, and the calculation method of electromagnetic radiation is given. The results show that the addition of magnetic field can not only enhance the radiation, Finally, the monochromatic light field can be changed by reducing the pulse width and introducing the linear chirp. To explore the effects on low frequency radiation. Chirp results in the broadening of the laser spectrum in the high and low frequency directions, while the periodic femtosecond laser waveform itself is asymmetrical, which leads to the enhancement of terahertz radiation. Moreover, the effects of these two actions are cumulative. In addition, it has been found that the broadening of the high frequency direction increases with the increase of chirp parameters. However, the broadening of low-frequency direction shows a tendency of intermittent fluctuation. In this paper, several methods of enhancing terahertz radiation are found through theoretical research, and the results are explained. It provides a basis for further theoretical and experimental research in the future.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN24

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