本文選題：光學(xué)超晶格　切入點：圖案極化鈮酸鋰　出處：《南京大學(xué)》2017年碩士論文

【摘要】：光學(xué)超晶格主要是指二階非線性系數(shù)受到人工調(diào)制的微結(jié)構(gòu)材料,其調(diào)制周期與光波的波長相比擬,通常為微米量級。鈮酸鋰(Lithium Niobate,LN)是最常用的光學(xué)超晶格材料之一,可以用來研究非線性光學(xué)現(xiàn)象,并恰好可以通過準(zhǔn)位相匹配理論去補償非線性過程中的位相失配,以此來產(chǎn)生或是調(diào)控非線性光學(xué)效應(yīng)。本論文主要研究的是通過鐵電疇反轉(zhuǎn)制備光學(xué)超晶格,以及其在非線性光學(xué)方面的應(yīng)用。具體包括以下幾個部分:1.介紹介電體超晶格的概念與發(fā)展歷程,從一維的周期結(jié)構(gòu)到任意的二維結(jié)構(gòu),并著眼于其在非線性光學(xué)方面的應(yīng)用,然后結(jié)合準(zhǔn)位相匹配的理論,分析了光學(xué)超晶格在非線性頻率轉(zhuǎn)換中的作用;2.梳理了通過鐵電疇反轉(zhuǎn)制備光學(xué)超晶格的方法,包括生長條紋法、化學(xué)擴散法、電子束直寫法、外加電場極化法等,重點研究了鈮酸鋰疇極化的過程與性質(zhì),主要包括五個過程:分別是反轉(zhuǎn)疇的成核、反轉(zhuǎn)疇的縱向生長、反轉(zhuǎn)疇的橫向擴張、反轉(zhuǎn)疇的橫向合并與自發(fā)的背向反轉(zhuǎn)效應(yīng);3.詳細介紹了我們制備圖案極化鈮酸鋰薄膜的工藝流程,在外加電場極化法的基礎(chǔ)上,我們不斷改進工藝水平,優(yōu)化工藝參數(shù),能夠在30-50 μm厚的鈮酸鋰晶體薄膜中,制備出任意的、二維的、均勻的、貫穿的、長期穩(wěn)定存在鐵電疇結(jié)構(gòu)。通過選擇性刻蝕之后,我們可以在光學(xué)顯微鏡下清晰地看到鈮酸鋰晶體薄膜的鐵電疇結(jié)構(gòu);4.我們的制備方法具有很多優(yōu)點,相比于傳統(tǒng)的500 μm厚的鈮酸鋰晶體,這種極化方法易于操作,不需要苛刻的外部條件,本論文中所有的極化過程都是在常溫常壓下進行的。這種厚度的的LN晶體薄膜的鐵電疇結(jié)構(gòu)能夠長期穩(wěn)定的存在,不會消退;5.理論上分析了非共線的非線性倍頻過程,主要包括非線性拉曼奈斯衍射及非線性切倫科夫衍射,分別是橫向的位相匹配與縱向的位相匹配過程。然后我們利用制備的圖案極化鈮酸鋰薄膜進行了實驗驗證,實驗結(jié)果與理論計算十分吻合;6.最后,我們將全息技術(shù)引入非線性光學(xué)領(lǐng)域,基于制備的圖案極化鈮酸鋰薄膜,可以對倍頻光進行波前整形。在實驗上,我們通過叉形光柵結(jié)構(gòu)產(chǎn)生了倍頻渦旋光,并設(shè)計了同心圓結(jié)構(gòu)與分立點陣結(jié)構(gòu)的鐵電疇,產(chǎn)生了不同的非線性波前。
[Abstract]:Optical superlattices mainly refer to microstructured materials whose second-order nonlinear coefficients are manually modulated. The modulation period of optical superlattices is comparable to the wavelength of light waves and is usually of the order of micron magnitude.Lithium Niobate LN) is one of the most commonly used optical superlattice materials, which can be used to study nonlinear optical phenomena and compensate for phase mismatch in nonlinear process by quasi-phase matching theory.In this way, nonlinear optical effects are produced or regulated.In this thesis, we mainly study the fabrication of optical superlattices by ferroelectric domain inversion and their applications in nonlinear optics.It includes the following parts: 1.This paper introduces the concept and development of dielectric superlattice, from one-dimensional periodic structure to arbitrary two-dimensional structure, and focuses on its application in nonlinear optics, and then combines the theory of quasi-phase matching.The role of optical superlattices in nonlinear frequency conversion is analyzed.The methods of preparing optical superlattices by ferroelectric domain inversion, including growth stripe method, chemical diffusion method, electron beam direct-writing method, applied electric field polarization method and so on, were reviewed. The process and properties of domain polarization of lithium niobate were studied.There are five main processes: nucleation of reverse domain, longitudinal growth of reverse domain, transverse expansion of reverse domain, transverse combination of reverse domain and spontaneous reverse effect.The process of fabricating patterned lithium niobate thin films is introduced in detail. On the basis of the applied electric field polarization method, we continuously improve the process level and optimize the process parameters, which can be used in 30 ~ 50 渭 m thick lithium niobate crystal thin films.Arbitrary, two-dimensional, uniform, penetrating and stable ferroelectric domain structures have been prepared.After selective etching, the ferroelectric domain structure of lithium niobate thin films can be clearly observed under optical microscope.Compared with the traditional 500 渭 m thick lithium niobate crystal, this method is easy to operate and does not require harsh external conditions. All the polarization processes in this paper are carried out under normal temperature and atmospheric pressure.The ferroelectric domain structure of this thickness LN crystal thin film can exist steadily for a long time and will not fade away.The nonlinear frequency doubling process of noncollinear is analyzed theoretically, including nonlinear Raman diffraction and nonlinear Cherenkov diffraction, which are transverse phase matching and longitudinal phase matching, respectively.Then we use the patterned poled lithium niobate film to verify the experimental results, and the experimental results are in good agreement with the theoretical calculation.Finally, the holographic technique is introduced into the field of nonlinear optics. Based on the pattern-polarized lithium niobate thin films, the wavefront shaping of frequency-doubled light can be carried out.In the experiment, we have generated the frequency doubling vortex light through the forked grating structure, and designed the ferroelectric domains with concentric circle structure and discrete lattice structure, and produced different nonlinear wavefront.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O484
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本文編號：1705823