基于PPLN晶體和雙波長(zhǎng)光纖激光器的可調(diào)諧THz輻射
發(fā)布時(shí)間：2019-02-24 20:15
【摘要】：太赫茲波具有很多獨(dú)特性質(zhì),如寬帶性、互補(bǔ)性、瞬態(tài)性、相干性等。在成像與感測(cè)等應(yīng)用領(lǐng)域和醫(yī)藥、化學(xué)與生命科學(xué)等基礎(chǔ)研究領(lǐng),以及國(guó)防技術(shù)領(lǐng)域都帶來了比較深遠(yuǎn)的影響。因此,THz科學(xué)與技術(shù)成為最近幾年比較熱門的研究課題。目前,THz有眾多熱門且有實(shí)際應(yīng)用價(jià)值的研究方向,包括THz輻射源、THz隱身以及THz波導(dǎo)等研究。其中,怎樣才能獲得可調(diào)諧的THz輻射源是THz科學(xué)與技術(shù)研究的關(guān)鍵性問題。經(jīng)過許多人的實(shí)驗(yàn)研究驗(yàn)證,非線性光學(xué)差頻獲得THz波輻射的方法是一種比較理想的方法,其優(yōu)點(diǎn)是能夠在常溫下穩(wěn)定運(yùn)轉(zhuǎn)且輸出可調(diào)諧和相干的THz波。非線性光學(xué)差頻方法產(chǎn)生THz輻射的原理是由兩束波長(zhǎng)接近、相干性好的激光通過非線性晶體在滿足相位匹配的條件下差頻獲得THz波。大多數(shù)選用的激光器是固體以及氣體激光器,采用光纖激光器的方法還比較少,尤其是采用1550nm附近的雙波長(zhǎng)單縱模摻鉺光纖激光器。 本文重點(diǎn)研究了基于PPLN晶體和雙波長(zhǎng)光纖激光器的可調(diào)諧THz輻射源,探討了PPLN晶體的相關(guān)特性如何影響THz輻射,并對(duì)基于PPLN晶體實(shí)現(xiàn)THz波的調(diào)諧進(jìn)行分析。通過分析非線性差頻對(duì)雙波長(zhǎng)源的要求以及雙波長(zhǎng)光纖激光器,得出雙波長(zhǎng)單縱模摻鉺光纖激光器是差頻生成系統(tǒng)(DFG)較為理想的雙波長(zhǎng)源。最終,本文設(shè)計(jì)出一種基于非線性放大環(huán)鏡(NALM)的雙波長(zhǎng)單縱模摻鉺光纖激光器。由此,為將來可調(diào)諧THz輻射源的光纖化工作打下基礎(chǔ)。 論文的主要工作有： (1)對(duì)非線性差頻理論進(jìn)行研究,建立滿足相位匹配時(shí)的非線性三波互作用的穩(wěn)態(tài)耦合波方程,從而得出生成THz波輻射的條件,并介紹了相位匹配的方法。在準(zhǔn)相位匹配理論分析的基礎(chǔ)上,討論了PPLN晶體的相關(guān)特性對(duì)準(zhǔn)相位匹配的影響,如折射率和相干長(zhǎng)度等,從而得到如何優(yōu)化PPLN晶體結(jié)構(gòu)的方法。 (2)對(duì)THz波調(diào)諧方式進(jìn)行分析,重點(diǎn)分析了溫度調(diào)諧,極化周期調(diào)諧以及二者結(jié)合方式的調(diào)諧。并分析THz波譜寬,得到基于PPLN晶體差頻生成THz輻射源的THz波普?qǐng)D。以及得到PPLN晶體相位失配時(shí)的極化周期允許帶寬,最后對(duì)THz輸出功率進(jìn)行了分析。 (3)對(duì)用于差頻生成THz輻射的雙波長(zhǎng)源進(jìn)行分析,得出雙波長(zhǎng)摻鉺光纖激光器是一種比較理想的雙波長(zhǎng)源。設(shè)計(jì)了一種基于非線性放大環(huán)鏡的雙波長(zhǎng)單縱模摻鉺光纖激光器,從而得到1550nm附近的雙波長(zhǎng)光纖激光器,經(jīng)過測(cè)量?jī)x的測(cè)量分析得到的雙波長(zhǎng)是否滿足DFG系統(tǒng)中雙波長(zhǎng)源的要求,為以后THz輻射源的光纖化工作打下基礎(chǔ)。
[Abstract]:Terahertz wave has many unique properties, such as wideband, complementarity, transient, coherence and so on. In the field of imaging and sensing applications, medicine, chemistry and life sciences, and national defense technology have brought more far-reaching impact. Therefore, THz science and technology has become a hot research topic in recent years. At present, THz has many hot and practical applications, including THz radiation sources, THz stealth and THz waveguides. Among them, how to obtain tunable THz radiation source is a key problem in THz science and technology research. It has been proved by many experiments that the method of obtaining THz wave radiation by nonlinear optical differential frequency is an ideal method. The advantage of this method is that it can operate stably at room temperature and output tunable and coherent THz waves. The principle of generating THz radiation by nonlinear optical differential frequency method is that the THz wave is obtained by using a laser with good coherence and two wavelengths close to each other. Most of the lasers used are solid and gas lasers, and the methods of using fiber lasers are relatively few, especially the dual-wavelength single-longitudinal-mode erbium-doped fiber lasers near 1550nm. In this paper, the tunable THz radiation source based on PPLN crystal and dual-wavelength fiber laser is studied, and how the related characteristics of PPLN crystal affect the THz radiation is discussed, and the tuning of THz wave based on PPLN crystal is analyzed. By analyzing the requirement of nonlinear differential frequency for dual wavelength source and dual wavelength fiber laser, it is concluded that dual wavelength single longitudinal mode erbium doped fiber laser is an ideal dual wavelength source for (DFG). Finally, a dual wavelength single longitudinal mode erbium doped fiber laser based on nonlinear amplifying loop mirror (NALM) is designed. Therefore, it will lay a foundation for the fiber conversion of tunable THz radiation sources in the future. The main work of this paper is as follows: (1) the nonlinear differential frequency theory is studied, and the steady-state coupling wave equation satisfying the nonlinear three-wave interaction in phase matching is established, and the conditions for generating THz wave radiation are obtained. The method of phase matching is also introduced. Based on the theoretical analysis of quasi-phase matching, the effects of correlation characteristics of PPLN crystal on phase matching, such as refractive index and coherent length, are discussed, and the method of optimizing the structure of PPLN crystal is obtained. (2) the tunable mode of THz wave is analyzed, especially the temperature tuning, the polarization period tuning and the combination tuning. The spectrum width of THz is analyzed, and the THz wave diagram of THz radiation source is obtained based on the difference frequency of PPLN crystal. The allowable bandwidth of polarization period for phase mismatch of PPLN crystal is obtained. Finally, the output power of THz is analyzed. (3) the dual-wavelength source used to generate THz radiation from the differential frequency is analyzed, and it is concluded that the dual-wavelength erbium-doped fiber laser is an ideal dual-wavelength source. A dual-wavelength single-longitudinal-mode erbium-doped fiber laser based on nonlinear amplifying loop mirror is designed, and a dual-wavelength fiber laser near 1550nm is obtained. Whether the dual-wavelength can meet the requirements of the dual-wavelength source in DFG system can be obtained by the measurement and analysis of the instrument, which will lay a foundation for the future work of the THz radiation source.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN248
本文編號(hào)：2429893
[Abstract]:Terahertz wave has many unique properties, such as wideband, complementarity, transient, coherence and so on. In the field of imaging and sensing applications, medicine, chemistry and life sciences, and national defense technology have brought more far-reaching impact. Therefore, THz science and technology has become a hot research topic in recent years. At present, THz has many hot and practical applications, including THz radiation sources, THz stealth and THz waveguides. Among them, how to obtain tunable THz radiation source is a key problem in THz science and technology research. It has been proved by many experiments that the method of obtaining THz wave radiation by nonlinear optical differential frequency is an ideal method. The advantage of this method is that it can operate stably at room temperature and output tunable and coherent THz waves. The principle of generating THz radiation by nonlinear optical differential frequency method is that the THz wave is obtained by using a laser with good coherence and two wavelengths close to each other. Most of the lasers used are solid and gas lasers, and the methods of using fiber lasers are relatively few, especially the dual-wavelength single-longitudinal-mode erbium-doped fiber lasers near 1550nm. In this paper, the tunable THz radiation source based on PPLN crystal and dual-wavelength fiber laser is studied, and how the related characteristics of PPLN crystal affect the THz radiation is discussed, and the tuning of THz wave based on PPLN crystal is analyzed. By analyzing the requirement of nonlinear differential frequency for dual wavelength source and dual wavelength fiber laser, it is concluded that dual wavelength single longitudinal mode erbium doped fiber laser is an ideal dual wavelength source for (DFG). Finally, a dual wavelength single longitudinal mode erbium doped fiber laser based on nonlinear amplifying loop mirror (NALM) is designed. Therefore, it will lay a foundation for the fiber conversion of tunable THz radiation sources in the future. The main work of this paper is as follows: (1) the nonlinear differential frequency theory is studied, and the steady-state coupling wave equation satisfying the nonlinear three-wave interaction in phase matching is established, and the conditions for generating THz wave radiation are obtained. The method of phase matching is also introduced. Based on the theoretical analysis of quasi-phase matching, the effects of correlation characteristics of PPLN crystal on phase matching, such as refractive index and coherent length, are discussed, and the method of optimizing the structure of PPLN crystal is obtained. (2) the tunable mode of THz wave is analyzed, especially the temperature tuning, the polarization period tuning and the combination tuning. The spectrum width of THz is analyzed, and the THz wave diagram of THz radiation source is obtained based on the difference frequency of PPLN crystal. The allowable bandwidth of polarization period for phase mismatch of PPLN crystal is obtained. Finally, the output power of THz is analyzed. (3) the dual-wavelength source used to generate THz radiation from the differential frequency is analyzed, and it is concluded that the dual-wavelength erbium-doped fiber laser is an ideal dual-wavelength source. A dual-wavelength single-longitudinal-mode erbium-doped fiber laser based on nonlinear amplifying loop mirror is designed, and a dual-wavelength fiber laser near 1550nm is obtained. Whether the dual-wavelength can meet the requirements of the dual-wavelength source in DFG system can be obtained by the measurement and analysis of the instrument, which will lay a foundation for the future work of the THz radiation source.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TN248
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